[NTVDM]: DOS: Implement INT 29h: DOS 2+ Fast Console Output.
[reactos.git] / subsystems / ntvdm / dos.c
index d89c8c2..c871d3d 100644 (file)
@@ -8,19 +8,60 @@
 
 /* INCLUDES *******************************************************************/
 
+#define NDEBUG
+
+#include "emulator.h"
 #include "dos.h"
+
 #include "bios.h"
-#include "emulator.h"
+#include "bop.h"
+#include "int32.h"
+#include "registers.h"
 
 /* PRIVATE VARIABLES **********************************************************/
 
 static WORD CurrentPsp = SYSTEM_PSP;
+static WORD DosLastError = 0;
 static DWORD DiskTransferArea;
+static BYTE CurrentDrive;
+static CHAR LastDrive = 'E';
+static CHAR CurrentDirectories[NUM_DRIVES][DOS_DIR_LENGTH];
 static HANDLE DosSystemFileTable[DOS_SFT_SIZE];
 static WORD DosSftRefCount[DOS_SFT_SIZE];
+static BYTE DosAllocStrategy = DOS_ALLOC_BEST_FIT;
+static BOOLEAN DosUmbLinked = FALSE;
+static WORD DosErrorLevel = 0x0000;
+
+/* BOP Identifiers */
+#define BOP_DOS 0x50    // DOS System BOP (for NTIO.SYS and NTDOS.SYS)
+#define BOP_CMD 0x54    // DOS Command Interpreter BOP (for COMMAND.COM)
 
 /* PRIVATE FUNCTIONS **********************************************************/
 
+/* Taken from base/shell/cmd/console.c */
+static BOOL IsConsoleHandle(HANDLE hHandle)
+{
+    DWORD dwMode;
+
+    /* Check whether the handle may be that of a console... */
+    if ((GetFileType(hHandle) & FILE_TYPE_CHAR) == 0) return FALSE;
+
+    /*
+     * It may be. Perform another test... The idea comes from the
+     * MSDN description of the WriteConsole API:
+     *
+     * "WriteConsole fails if it is used with a standard handle
+     *  that is redirected to a file. If an application processes
+     *  multilingual output that can be redirected, determine whether
+     *  the output handle is a console handle (one method is to call
+     *  the GetConsoleMode function and check whether it succeeds).
+     *  If the handle is a console handle, call WriteConsole. If the
+     *  handle is not a console handle, the output is redirected and
+     *  you should call WriteFile to perform the I/O."
+     */
+    return GetConsoleMode(hHandle, &dwMode);
+}
+
 static VOID DosCombineFreeBlocks(WORD StartBlock)
 {
     PDOS_MCB CurrentMcb = SEGMENT_TO_MCB(StartBlock), NextMcb;
@@ -49,13 +90,13 @@ static VOID DosCombineFreeBlocks(WORD StartBlock)
     }
 }
 
-static WORD DosCopyEnvironmentBlock(WORD SourceSegment)
+static WORD DosCopyEnvironmentBlock(WORD SourceSegment, LPCSTR ProgramName)
 {
     PCHAR Ptr, SourceBuffer, DestBuffer = NULL;
     ULONG TotalSize = 0;
     WORD DestSegment;
 
-    Ptr = SourceBuffer = (PCHAR)((ULONG_PTR)BaseAddress + TO_LINEAR(SourceSegment, 0));
+    Ptr = SourceBuffer = (PCHAR)SEG_OFF_TO_PTR(SourceSegment, 0);
 
     /* Calculate the size of the environment block */
     while (*Ptr)
@@ -65,28 +106,34 @@ static WORD DosCopyEnvironmentBlock(WORD SourceSegment)
     }
     TotalSize++;
 
+    /* Add the string buffer size */
+    TotalSize += strlen(ProgramName) + 1;
+
     /* Allocate the memory for the environment block */
-    DestSegment = DosAllocateMemory((TotalSize + 0x0F) >> 4, NULL);
+    DestSegment = DosAllocateMemory((WORD)((TotalSize + 0x0F) >> 4), NULL);
     if (!DestSegment) return 0;
 
     Ptr = SourceBuffer;
 
-    DestBuffer = (PCHAR)((ULONG_PTR)BaseAddress + TO_LINEAR(DestSegment, 0));
+    DestBuffer = (PCHAR)SEG_OFF_TO_PTR(DestSegment, 0);
     while (*Ptr)
     {
         /* Copy the string */
         strcpy(DestBuffer, Ptr);
 
         /* Advance to the next string */
-        Ptr += strlen(Ptr) + 1;
         DestBuffer += strlen(Ptr);
+        Ptr += strlen(Ptr) + 1;
 
         /* Put a zero after the string */
         *(DestBuffer++) = 0;
     }
 
     /* Set the final zero */
-    *DestBuffer = 0;
+    *(DestBuffer++) = 0;
+
+    /* Copy the program name after the environment block */
+    strcpy(DestBuffer, ProgramName);
 
     return DestSegment;
 }
@@ -194,7 +241,7 @@ static VOID DosCopyHandleTable(LPBYTE DestinationTable)
         for (i = 0; i <= 2; i++)
         {
             /* Set the index in the SFT */
-            DestinationTable[i] = i;
+            DestinationTable[i] = (BYTE)i;
 
             /* Increase the reference count */
             DosSftRefCount[i]++;
@@ -224,6 +271,16 @@ WORD DosAllocateMemory(WORD Size, WORD *MaxAvailable)
 {
     WORD Result = 0, Segment = FIRST_MCB_SEGMENT, MaxSize = 0;
     PDOS_MCB CurrentMcb, NextMcb;
+    BOOLEAN SearchUmb = FALSE;
+
+    DPRINT("DosAllocateMemory: Size 0x%04X\n", Size);
+
+    if (DosUmbLinked && (DosAllocStrategy & (DOS_ALLOC_HIGH | DOS_ALLOC_HIGH_LOW)))
+    {
+        /* Search UMB first */
+        Segment = UMB_START_SEGMENT;
+        SearchUmb = TRUE;
+    }
 
     while (TRUE)
     {
@@ -233,6 +290,8 @@ WORD DosAllocateMemory(WORD Size, WORD *MaxAvailable)
         /* Make sure it's valid */
         if (CurrentMcb->BlockType != 'M' && CurrentMcb->BlockType != 'Z')
         {
+            DPRINT("The DOS memory arena is corrupted!\n");
+            DosLastError = ERROR_ARENA_TRASHED;
             return 0;
         }
 
@@ -248,23 +307,59 @@ WORD DosAllocateMemory(WORD Size, WORD *MaxAvailable)
         /* Check if this block is big enough */
         if (CurrentMcb->Size < Size) goto Next;
 
-        /* It is, update the smallest found so far */
-        if ((Result == 0) || (CurrentMcb->Size < SEGMENT_TO_MCB(Result)->Size))
+        switch (DosAllocStrategy & 0x3F)
         {
-            Result = Segment;
+            case DOS_ALLOC_FIRST_FIT:
+            {
+                /* For first fit, stop immediately */
+                Result = Segment;
+                goto Done;
+            }
+
+            case DOS_ALLOC_BEST_FIT:
+            {
+                /* For best fit, update the smallest block found so far */
+                if ((Result == 0) || (CurrentMcb->Size < SEGMENT_TO_MCB(Result)->Size))
+                {
+                    Result = Segment;
+                }
+
+                break;
+            }
+
+            case DOS_ALLOC_LAST_FIT:
+            {
+                /* For last fit, make the current block the result, but keep searching */
+                Result = Segment;
+                break;
+            }
         }
 
 Next:
         /* If this was the last MCB in the chain, quit */
-        if (CurrentMcb->BlockType == 'Z') break;
+        if (CurrentMcb->BlockType == 'Z')
+        {
+            /* Check if nothing was found while searching through UMBs */
+            if ((Result == 0) && SearchUmb && (DosAllocStrategy & DOS_ALLOC_HIGH_LOW))
+            {
+                /* Search low memory */
+                Segment = FIRST_MCB_SEGMENT;
+                continue;
+            }
+
+            break;
+        }
 
         /* Otherwise, update the segment and continue */
         Segment += CurrentMcb->Size + 1;
     }
 
+Done:
+
     /* If we didn't find a free block, return 0 */
     if (Result == 0)
     {
+        DosLastError = ERROR_NOT_ENOUGH_MEMORY;
         if (MaxAvailable) *MaxAvailable = MaxSize;
         return 0;
     }
@@ -301,10 +396,15 @@ BOOLEAN DosResizeMemory(WORD BlockData, WORD NewSize, WORD *MaxAvailable)
     WORD Segment = BlockData - 1, ReturnSize = 0, NextSegment;
     PDOS_MCB Mcb = SEGMENT_TO_MCB(Segment), NextMcb;
 
+    DPRINT("DosResizeMemory: BlockData 0x%04X, NewSize 0x%04X\n",
+           BlockData,
+           NewSize);
+
     /* Make sure this is a valid, allocated block */
     if ((Mcb->BlockType != 'M' && Mcb->BlockType != 'Z') || Mcb->OwnerPsp == 0)
     {
         Success = FALSE;
+        DosLastError = ERROR_INVALID_HANDLE;
         goto Done;
     }
 
@@ -327,6 +427,8 @@ BOOLEAN DosResizeMemory(WORD BlockData, WORD NewSize, WORD *MaxAvailable)
         /* Make sure the next segment is free */
         if (NextMcb->OwnerPsp != 0)
         {
+            DPRINT("Cannot expand memory block: next segment is not free!\n");
+            DosLastError = ERROR_NOT_ENOUGH_MEMORY;
             Success = FALSE;
             goto Done;
         }
@@ -347,6 +449,10 @@ BOOLEAN DosResizeMemory(WORD BlockData, WORD NewSize, WORD *MaxAvailable)
         /* Check if the block is larger than requested */
         if (Mcb->Size > NewSize)
         {
+            DPRINT("Block too large, reducing size from 0x%04X to 0x%04X\n",
+                   Mcb->Size,
+                   NewSize);
+
             /* It is, split it into two blocks */
             NextMcb = SEGMENT_TO_MCB(Segment + NewSize + 1);
     
@@ -362,6 +468,10 @@ BOOLEAN DosResizeMemory(WORD BlockData, WORD NewSize, WORD *MaxAvailable)
     }
     else if (NewSize < Mcb->Size)
     {
+        DPRINT("Shrinking block from 0x%04X to 0x%04X\n",
+                Mcb->Size,
+                NewSize);
+
         /* Just split the block */
         NextMcb = SEGMENT_TO_MCB(Segment + NewSize + 1);
         NextMcb->BlockType = Mcb->BlockType;
@@ -377,6 +487,9 @@ Done:
     /* Check if the operation failed */
     if (!Success)
     {
+        DPRINT("DosResizeMemory FAILED. Maximum available: 0x%04X\n",
+               ReturnSize);
+
         /* Return the maximum possible size */
         if (MaxAvailable) *MaxAvailable = ReturnSize;
     }
@@ -388,8 +501,14 @@ BOOLEAN DosFreeMemory(WORD BlockData)
 {
     PDOS_MCB Mcb = SEGMENT_TO_MCB(BlockData - 1);
 
+    DPRINT("DosFreeMemory: BlockData 0x%04X\n", BlockData);
+
     /* Make sure the MCB is valid */
-    if (Mcb->BlockType != 'M' && Mcb->BlockType != 'Z') return FALSE;
+    if (Mcb->BlockType != 'M' && Mcb->BlockType != 'Z')
+    {
+        DPRINT("MCB block type '%c' not valid!\n", Mcb->BlockType);
+        return FALSE;
+    }
 
     /* Mark the block as free */
     Mcb->OwnerPsp = 0;
@@ -397,11 +516,73 @@ BOOLEAN DosFreeMemory(WORD BlockData)
     return TRUE;
 }
 
+BOOLEAN DosLinkUmb(VOID)
+{
+    DWORD Segment = FIRST_MCB_SEGMENT;
+    PDOS_MCB Mcb = SEGMENT_TO_MCB(Segment);
+
+    DPRINT("Linking UMB\n");
+
+    /* Check if UMBs are already linked */
+    if (DosUmbLinked) return FALSE;
+
+    /* Find the last block */
+    while ((Mcb->BlockType == 'M') && (Segment <= 0xFFFF))
+    {
+        Segment += Mcb->Size + 1;
+        Mcb = SEGMENT_TO_MCB(Segment);
+    }
+
+    /* Make sure it's valid */
+    if (Mcb->BlockType != 'Z') return FALSE;
+
+    /* Connect the MCB with the UMB chain */
+    Mcb->BlockType = 'M';
+
+    DosUmbLinked = TRUE;
+    return TRUE;
+}
+
+BOOLEAN DosUnlinkUmb(VOID)
+{
+    DWORD Segment = FIRST_MCB_SEGMENT;
+    PDOS_MCB Mcb = SEGMENT_TO_MCB(Segment);
+
+    DPRINT("Unlinking UMB\n");
+
+    /* Check if UMBs are already unlinked */
+    if (!DosUmbLinked) return FALSE;
+
+    /* Find the block preceding the MCB that links it with the UMB chain */
+    while (Segment <= 0xFFFF)
+    {
+        if ((Segment + Mcb->Size) == (FIRST_MCB_SEGMENT + USER_MEMORY_SIZE))
+        {
+            /* This is the last non-UMB segment */
+            break;
+        }
+
+        /* Advance to the next MCB */
+        Segment += Mcb->Size + 1;
+        Mcb = SEGMENT_TO_MCB(Segment);
+    }
+
+    /* Mark the MCB as the last MCB */
+    Mcb->BlockType = 'Z';
+
+    DosUmbLinked = FALSE;
+    return TRUE;
+}
+
 WORD DosCreateFile(LPWORD Handle, LPCSTR FilePath, WORD Attributes)
 {
     HANDLE FileHandle;
     WORD DosHandle;
 
+    DPRINT("DosCreateFile: FilePath \"%s\", Attributes 0x%04X\n",
+            FilePath,
+            Attributes);
+
     /* Create the file */
     FileHandle = CreateFileA(FilePath,
                              GENERIC_READ | GENERIC_WRITE,
@@ -414,7 +595,7 @@ WORD DosCreateFile(LPWORD Handle, LPCSTR FilePath, WORD Attributes)
     if (FileHandle == INVALID_HANDLE_VALUE)
     {
         /* Return the error code */
-        return GetLastError();
+        return (WORD)GetLastError();
     }
 
     /* Open the DOS handle */
@@ -440,6 +621,10 @@ WORD DosOpenFile(LPWORD Handle, LPCSTR FilePath, BYTE AccessMode)
     ACCESS_MASK Access = 0;
     WORD DosHandle;
 
+    DPRINT("DosOpenFile: FilePath \"%s\", AccessMode 0x%04X\n",
+            FilePath,
+            AccessMode);
+
     /* Parse the access mode */
     switch (AccessMode & 3)
     {
@@ -483,7 +668,7 @@ WORD DosOpenFile(LPWORD Handle, LPCSTR FilePath, BYTE AccessMode)
     if (FileHandle == INVALID_HANDLE_VALUE)
     {
         /* Return the error code */
-        return GetLastError();
+        return (WORD)GetLastError();
     }
 
     /* Open the DOS handle */
@@ -509,14 +694,16 @@ WORD DosReadFile(WORD FileHandle, LPVOID Buffer, WORD Count, LPWORD BytesRead)
     DWORD BytesRead32 = 0;
     HANDLE Handle = DosGetRealHandle(FileHandle);
 
+    DPRINT("DosReadFile: FileHandle 0x%04X, Count 0x%04X\n", FileHandle, Count);
+
     /* Make sure the handle is valid */
-    if (Handle == INVALID_HANDLE_VALUE) return ERROR_INVALID_PARAMETER;
+    if (Handle == INVALID_HANDLE_VALUE) return ERROR_INVALID_HANDLE;
 
     /* Read the file */
     if (!ReadFile(Handle, Buffer, Count, &BytesRead32, NULL))
     {
         /* Store the error code */
-        Result = GetLastError();
+        Result = (WORD)GetLastError();
     }
 
     /* The number of bytes read is always 16-bit */
@@ -531,15 +718,32 @@ WORD DosWriteFile(WORD FileHandle, LPVOID Buffer, WORD Count, LPWORD BytesWritte
     WORD Result = ERROR_SUCCESS;
     DWORD BytesWritten32 = 0;
     HANDLE Handle = DosGetRealHandle(FileHandle);
+    WORD i;
+
+    DPRINT("DosWriteFile: FileHandle 0x%04X, Count 0x%04X\n",
+           FileHandle,
+           Count);
 
     /* Make sure the handle is valid */
-    if (Handle == INVALID_HANDLE_VALUE) return ERROR_INVALID_PARAMETER;
+    if (Handle == INVALID_HANDLE_VALUE) return ERROR_INVALID_HANDLE;
 
-    /* Write the file */
-    if (!WriteFile(Handle, Buffer, Count, &BytesWritten32, NULL))
+    if (IsConsoleHandle(Handle))
     {
-        /* Store the error code */
-        Result = GetLastError();
+        for (i = 0; i < Count; i++)
+        {
+            /* Call the BIOS to print the character */
+            BiosPrintCharacter(((LPBYTE)Buffer)[i], DOS_CHAR_ATTRIBUTE, Bda->VideoPage);
+            BytesWritten32++;
+        }
+    }
+    else
+    {
+        /* Write the file */
+        if (!WriteFile(Handle, Buffer, Count, &BytesWritten32, NULL))
+        {
+            /* Store the error code */
+            Result = (WORD)GetLastError();
+        }
     }
 
     /* The number of bytes written is always 16-bit */
@@ -549,12 +753,113 @@ WORD DosWriteFile(WORD FileHandle, LPVOID Buffer, WORD Count, LPWORD BytesWritte
     return Result;
 }
 
+WORD DosSeekFile(WORD FileHandle, LONG Offset, BYTE Origin, LPDWORD NewOffset)
+{
+    WORD Result = ERROR_SUCCESS;
+    DWORD FilePointer;
+    HANDLE Handle = DosGetRealHandle(FileHandle);
+
+    DPRINT("DosSeekFile: FileHandle 0x%04X, Offset 0x%08X, Origin 0x%02X\n",
+           FileHandle,
+           Offset,
+           Origin);
+
+    /* Make sure the handle is valid */
+    if (Handle == INVALID_HANDLE_VALUE) return ERROR_INVALID_HANDLE;
+
+    /* Check if the origin is valid */
+    if (Origin != FILE_BEGIN && Origin != FILE_CURRENT && Origin != FILE_END)
+    {
+        return ERROR_INVALID_FUNCTION;
+    }
+
+    /* Move the file pointer */
+    FilePointer = SetFilePointer(Handle, Offset, NULL, Origin);
+
+    /* Check if there's a possibility the operation failed */
+    if (FilePointer == INVALID_SET_FILE_POINTER)
+    {
+        /* Get the real error code */
+        Result = (WORD)GetLastError();
+    }
+
+    if (Result != ERROR_SUCCESS)
+    {
+        /* The operation did fail */
+        return Result;
+    }
+
+    /* Return the file pointer, if requested */
+    if (NewOffset) *NewOffset = FilePointer;
+
+    /* Return success */
+    return ERROR_SUCCESS;
+}
+
+BOOLEAN DosFlushFileBuffers(WORD FileHandle)
+{
+    HANDLE Handle = DosGetRealHandle(FileHandle);
+
+    /* Make sure the handle is valid */
+    if (Handle == INVALID_HANDLE_VALUE) return FALSE;
+
+    /*
+     * No need to check whether the handle is a console handle since
+     * FlushFileBuffers() automatically does this check and calls
+     * FlushConsoleInputBuffer() for us.
+     */
+    // if (IsConsoleHandle(Handle))
+    //    return (BOOLEAN)FlushConsoleInputBuffer(Handle);
+    // else
+    return (BOOLEAN)FlushFileBuffers(Handle);
+}
+
+BOOLEAN DosDuplicateHandle(WORD OldHandle, WORD NewHandle)
+{
+    BYTE SftIndex;
+    PDOS_PSP PspBlock;
+    LPBYTE HandleTable;
+
+    DPRINT("DosDuplicateHandle: OldHandle 0x%04X, NewHandle 0x%04X\n",
+           OldHandle,
+           NewHandle);
+
+    /* The system PSP has no handle table */
+    if (CurrentPsp == SYSTEM_PSP) return FALSE;
+
+    /* Get a pointer to the handle table */
+    PspBlock = SEGMENT_TO_PSP(CurrentPsp);
+    HandleTable = (LPBYTE)FAR_POINTER(PspBlock->HandleTablePtr);
+
+    /* Make sure the old handle is open */
+    if (HandleTable[OldHandle] == 0xFF) return FALSE;
+
+    /* Check if the new handle is open */
+    if (HandleTable[NewHandle] != 0xFF)
+    {
+        /* Close it */
+        DosCloseHandle(NewHandle);
+    }
+
+    /* Increment the reference count of the SFT entry */
+    SftIndex = HandleTable[OldHandle];
+    DosSftRefCount[SftIndex]++;
+
+    /* Make the new handle point to that SFT entry */
+    HandleTable[NewHandle] = SftIndex;
+
+    /* Return success */
+    return TRUE;
+}
+
 BOOLEAN DosCloseHandle(WORD DosHandle)
 {
     BYTE SftIndex;
     PDOS_PSP PspBlock;
     LPBYTE HandleTable;
 
+    DPRINT("DosCloseHandle: DosHandle 0x%04X\n", DosHandle);
+
     /* The system PSP has no handle table */
     if (CurrentPsp == SYSTEM_PSP) return FALSE;
 
@@ -579,6 +884,96 @@ BOOLEAN DosCloseHandle(WORD DosHandle)
         DosSystemFileTable[SftIndex] = INVALID_HANDLE_VALUE;
     }
 
+    /* Clear the entry in the JFT */
+    HandleTable[DosHandle] = 0xFF;
+
+    return TRUE;
+}
+
+BOOLEAN DosChangeDrive(BYTE Drive)
+{
+    WCHAR DirectoryPath[DOS_CMDLINE_LENGTH];
+
+    /* Make sure the drive exists */
+    if (Drive > (LastDrive - 'A')) return FALSE;
+
+    /* Find the path to the new current directory */
+    swprintf(DirectoryPath, L"%c\\%S", Drive + 'A', CurrentDirectories[Drive]);
+
+    /* Change the current directory of the process */
+    if (!SetCurrentDirectory(DirectoryPath)) return FALSE;
+
+    /* Set the current drive */
+    CurrentDrive = Drive;
+
+    /* Return success */
+    return TRUE;
+}
+
+BOOLEAN DosChangeDirectory(LPSTR Directory)
+{
+    BYTE DriveNumber;
+    DWORD Attributes;
+    LPSTR Path;
+
+    /* Make sure the directory path is not too long */
+    if (strlen(Directory) >= DOS_DIR_LENGTH)
+    {
+        DosLastError = ERROR_PATH_NOT_FOUND;
+        return FALSE;
+    }
+
+    /* Get the drive number */
+    DriveNumber = Directory[0] - 'A';
+
+    /* Make sure the drive exists */
+    if (DriveNumber > (LastDrive - 'A'))
+    {
+        DosLastError = ERROR_PATH_NOT_FOUND;
+        return FALSE;
+    }
+
+    /* Get the file attributes */
+    Attributes = GetFileAttributesA(Directory);
+
+    /* Make sure the path exists and is a directory */
+    if ((Attributes == INVALID_FILE_ATTRIBUTES)
+        || !(Attributes & FILE_ATTRIBUTE_DIRECTORY))
+    {
+        DosLastError = ERROR_PATH_NOT_FOUND;
+        return FALSE;
+    }
+
+    /* Check if this is the current drive */
+    if (DriveNumber == CurrentDrive)
+    {
+        /* Change the directory */
+        if (!SetCurrentDirectoryA(Directory))
+        {
+            DosLastError = LOWORD(GetLastError());
+            return FALSE;
+        }
+    }
+
+    /* Get the directory part of the path */
+    Path = strchr(Directory, '\\');
+    if (Path != NULL)
+    {
+        /* Skip the backslash */
+        Path++;
+    }
+
+    /* Set the directory for the drive */
+    if (Path != NULL)
+    {
+        strncpy(CurrentDirectories[DriveNumber], Path, DOS_DIR_LENGTH);
+    }
+    else
+    {
+        CurrentDirectories[DriveNumber][0] = '\0';
+    }
+
+    /* Return success */
     return TRUE;
 }
 
@@ -598,8 +993,8 @@ VOID DosInitializePsp(WORD PspSegment, LPCSTR CommandLine, WORD ProgramSize, WOR
 
     /* Save the interrupt vectors */
     PspBlock->TerminateAddress = IntVecTable[0x22];
-    PspBlock->BreakAddress = IntVecTable[0x23];
-    PspBlock->CriticalAddress = IntVecTable[0x24];
+    PspBlock->BreakAddress     = IntVecTable[0x23];
+    PspBlock->CriticalAddress  = IntVecTable[0x24];
 
     /* Set the parent PSP */
     PspBlock->ParentPsp = CurrentPsp;
@@ -623,7 +1018,7 @@ VOID DosInitializePsp(WORD PspSegment, LPCSTR CommandLine, WORD ProgramSize, WOR
     PspBlock->FarCall[2] = 0xCB; // retf
 
     /* Set the command line */
-    PspBlock->CommandLineSize = strlen(CommandLine);
+    PspBlock->CommandLineSize = (BYTE)min(strlen(CommandLine), DOS_CMDLINE_LENGTH - 1);
     RtlCopyMemory(PspBlock->CommandLine, CommandLine, PspBlock->CommandLineSize);
     PspBlock->CommandLine[PspBlock->CommandLineSize] = '\r';
 }
@@ -633,16 +1028,21 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
     BOOLEAN Success = FALSE, AllocatedEnvBlock = FALSE;
     HANDLE FileHandle = INVALID_HANDLE_VALUE, FileMapping = NULL;
     LPBYTE Address = NULL;
-    LPSTR ProgramFilePath, Parameters[128];
-    CHAR CommandLineCopy[128];
+    LPSTR ProgramFilePath, Parameters[256];
+    CHAR CommandLineCopy[DOS_CMDLINE_LENGTH];
+    CHAR ParamString[DOS_CMDLINE_LENGTH];
     INT ParamCount = 0;
-    DWORD Segment = 0;
+    WORD Segment = 0;
     WORD MaxAllocSize;
     DWORD i, FileSize, ExeSize;
     PIMAGE_DOS_HEADER Header;
     PDWORD RelocationTable;
     PWORD RelocWord;
 
+    DPRINT("DosCreateProcess: CommandLine \"%s\", EnvBlock 0x%04X\n",
+           CommandLine,
+           EnvBlock);
+
     /* Save a copy of the command line */
     strcpy(CommandLineCopy, CommandLine);
 
@@ -650,12 +1050,21 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
     ProgramFilePath = strtok(CommandLineCopy, " \t");
 
     /* Load the parameters in the local array */
-    while ((ParamCount < 256)
+    while ((ParamCount < sizeof(Parameters)/sizeof(Parameters[0]))
            && ((Parameters[ParamCount] = strtok(NULL, " \t")) != NULL))
     {
         ParamCount++;
     }
 
+    ZeroMemory(ParamString, sizeof(ParamString));
+
+    /* Store the parameters in a string */
+    for (i = 0; i < ParamCount; i++)
+    {
+        strncat(ParamString, Parameters[i], DOS_CMDLINE_LENGTH - strlen(ParamString) - 1);
+        strncat(ParamString, " ", DOS_CMDLINE_LENGTH - strlen(ParamString) - 1);
+    }
+
     /* Open a handle to the executable */
     FileHandle = CreateFileA(ProgramFilePath,
                              GENERIC_READ,
@@ -691,7 +1100,8 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
         /* No, copy the one from the parent */
         EnvBlock = DosCopyEnvironmentBlock((CurrentPsp != SYSTEM_PSP)
                                            ? SEGMENT_TO_PSP(CurrentPsp)->EnvBlock
-                                           : SYSTEM_ENV_BLOCK);
+                                           : SYSTEM_ENV_BLOCK,
+                                           ProgramFilePath);
     }
 
     /* Check if this is an EXE file or a COM file */
@@ -718,7 +1128,7 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
         for (i = Header->e_maxalloc; i >= Header->e_minalloc; i--, ExeSize--)
         {
             /* Try to allocate that much memory */
-            Segment = DosAllocateMemory(ExeSize, NULL);
+            Segment = DosAllocateMemory((WORD)ExeSize, NULL);
             if (Segment != 0) break;
         }
 
@@ -727,8 +1137,8 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
 
         /* Initialize the PSP */
         DosInitializePsp(Segment,
-                         CommandLine,
-                         ExeSize,
+                         ParamString,
+                         (WORD)ExeSize,
                          EnvBlock);
 
         /* The process owns its own memory */
@@ -736,8 +1146,7 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
         DosChangeMemoryOwner(EnvBlock, Segment);
 
         /* Copy the program to Segment:0100 */
-        RtlCopyMemory((PVOID)((ULONG_PTR)BaseAddress
-                      + TO_LINEAR(Segment, 0x100)),
+        RtlCopyMemory(SEG_OFF_TO_PTR(Segment, 0x100),
                       Address + (Header->e_cparhdr << 4),
                       min(FileSize - (Header->e_cparhdr << 4),
                           (ExeSize << 4) - sizeof(DOS_PSP)));
@@ -749,17 +1158,16 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
         for (i = 0; i < Header->e_crlc; i++)
         {
             /* Get a pointer to the word that needs to be patched */
-            RelocWord = (PWORD)((ULONG_PTR)BaseAddress
-                                + TO_LINEAR(Segment + HIWORD(RelocationTable[i]),
-                                            0x100 + LOWORD(RelocationTable[i])));
+            RelocWord = (PWORD)SEG_OFF_TO_PTR(Segment + HIWORD(RelocationTable[i]),
+                                                0x100 + LOWORD(RelocationTable[i]));
 
             /* Add the number of the EXE segment to it */
             *RelocWord += Segment + (sizeof(DOS_PSP) >> 4);
         }
 
         /* Set the initial segment registers */
-        EmulatorSetRegister(EMULATOR_REG_DS, Segment);
-        EmulatorSetRegister(EMULATOR_REG_ES, Segment);
+        setDS(Segment);
+        setES(Segment);
 
         /* Set the stack to the location from the header */
         EmulatorSetStack(Segment + (sizeof(DOS_PSP) >> 4) + Header->e_ss,
@@ -781,7 +1189,7 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
         DosAllocateMemory(0xFFFF, &MaxAllocSize);
 
         /* Make sure it's enough for the whole program and the PSP */
-        if ((MaxAllocSize << 4) < (FileSize + sizeof(DOS_PSP))) goto Cleanup;
+        if (((DWORD)MaxAllocSize << 4) < (FileSize + sizeof(DOS_PSP))) goto Cleanup;
 
         /* Allocate all of it */
         Segment = DosAllocateMemory(MaxAllocSize, NULL);
@@ -792,24 +1200,29 @@ BOOLEAN DosCreateProcess(LPCSTR CommandLine, WORD EnvBlock)
         DosChangeMemoryOwner(EnvBlock, Segment);
 
         /* Copy the program to Segment:0100 */
-        RtlCopyMemory((PVOID)((ULONG_PTR)BaseAddress
-                      + TO_LINEAR(Segment, 0x100)),
+        RtlCopyMemory(SEG_OFF_TO_PTR(Segment, 0x100),
                       Address,
                       FileSize);
 
         /* Initialize the PSP */
         DosInitializePsp(Segment,
-                         CommandLine,
-                         (FileSize + sizeof(DOS_PSP)) >> 4,
+                         ParamString,
+                         MaxAllocSize,
                          EnvBlock);
 
         /* Set the initial segment registers */
-        EmulatorSetRegister(EMULATOR_REG_DS, Segment);
-        EmulatorSetRegister(EMULATOR_REG_ES, Segment);
+        setDS(Segment);
+        setES(Segment);
 
         /* Set the stack to the last word of the segment */
         EmulatorSetStack(Segment, 0xFFFE);
 
+        /*
+         * Set the value on the stack to 0, so that a near return
+         * jumps to PSP:0000 which has the exit code.
+         */
+        *((LPWORD)SEG_OFF_TO_PTR(Segment, 0xFFFE)) = 0;
+
         /* Execute */
         CurrentPsp = Segment;
         DiskTransferArea = MAKELONG(0x80, Segment);
@@ -840,15 +1253,24 @@ Cleanup:
 
 VOID DosTerminateProcess(WORD Psp, BYTE ReturnCode)
 {
+    WORD i;
     WORD McbSegment = FIRST_MCB_SEGMENT;
     PDOS_MCB CurrentMcb;
     LPDWORD IntVecTable = (LPDWORD)((ULONG_PTR)BaseAddress);
     PDOS_PSP PspBlock = SEGMENT_TO_PSP(Psp);
 
+    DPRINT("DosTerminateProcess: Psp 0x%04X, ReturnCode 0x%02X\n",
+           Psp,
+           ReturnCode);
+
     /* Check if this PSP is it's own parent */
     if (PspBlock->ParentPsp == Psp) goto Done;
 
-    // TODO: Close all handles opened by the process
+    for (i = 0; i < PspBlock->HandleTableSize; i++)
+    {
+        /* Close the handle */
+        DosCloseHandle(i);
+    }
 
     /* Free the memory used by the process */
     while (TRUE)
@@ -860,7 +1282,7 @@ VOID DosTerminateProcess(WORD Psp, BYTE ReturnCode)
         if (CurrentMcb->BlockType != 'M' && CurrentMcb->BlockType !='Z') break;
 
         /* If this block was allocated by the process, free it */
-        if (CurrentMcb->OwnerPsp == Psp) DosFreeMemory(McbSegment);
+        if (CurrentMcb->OwnerPsp == Psp) DosFreeMemory(McbSegment + 1);
 
         /* If this was the last block, quit */
         if (CurrentMcb->BlockType == 'Z') break;
@@ -882,22 +1304,53 @@ Done:
         if (CurrentPsp == SYSTEM_PSP) VdmRunning = FALSE;
     }
 
+    /* Save the return code - Normal termination */
+    DosErrorLevel = MAKEWORD(ReturnCode, 0x00);
+
     /* Return control to the parent process */
     EmulatorExecute(HIWORD(PspBlock->TerminateAddress),
                     LOWORD(PspBlock->TerminateAddress));
 }
 
-CHAR DosReadCharacter()
+CHAR DosReadCharacter(VOID)
 {
     CHAR Character = '\0';
     WORD BytesRead;
 
-    /* Use the file reading function */
-    DosReadFile(DOS_INPUT_HANDLE, &Character, sizeof(CHAR), &BytesRead);
+    if (IsConsoleHandle(DosGetRealHandle(DOS_INPUT_HANDLE)))
+    {
+        /* Call the BIOS */
+        Character = LOBYTE(BiosGetCharacter());
+    }
+    else
+    {
+        /* Use the file reading function */
+        DosReadFile(DOS_INPUT_HANDLE, &Character, sizeof(CHAR), &BytesRead);
+    }
 
     return Character;
 }
 
+BOOLEAN DosCheckInput(VOID)
+{
+    HANDLE Handle = DosGetRealHandle(DOS_INPUT_HANDLE);
+
+    if (IsConsoleHandle(Handle))
+    {
+        /* Call the BIOS */
+        return (BiosPeekCharacter() != 0xFFFF);
+    }
+    else
+    {
+        DWORD FileSizeHigh;
+        DWORD FileSize = GetFileSize(Handle, &FileSizeHigh);
+        LONG LocationHigh = 0;
+        DWORD Location = SetFilePointer(Handle, 0, &LocationHigh, FILE_CURRENT);
+
+        return ((Location != FileSize) || (LocationHigh != FileSizeHigh));
+    }
+}
+
 VOID DosPrintCharacter(CHAR Character)
 {
     WORD BytesWritten;
@@ -906,15 +1359,15 @@ VOID DosPrintCharacter(CHAR Character)
     DosWriteFile(DOS_OUTPUT_HANDLE, &Character, sizeof(CHAR), &BytesWritten);
 }
 
-VOID DosHandleIoctl(BYTE ControlCode, WORD FileHandle)
+BOOLEAN DosHandleIoctl(BYTE ControlCode, WORD FileHandle)
 {
     HANDLE Handle = DosGetRealHandle(FileHandle);
 
     if (Handle == INVALID_HANDLE_VALUE)
     {
         /* Doesn't exist */
-        EmulatorSetFlag(EMULATOR_FLAG_CF);
-        EmulatorSetRegister(EMULATOR_REG_AX, ERROR_FILE_NOT_FOUND);
+        DosLastError = ERROR_FILE_NOT_FOUND;
+        return FALSE;
     }
 
     switch (ControlCode)
@@ -939,10 +1392,8 @@ VOID DosHandleIoctl(BYTE ControlCode, WORD FileHandle)
             InfoWord |= 1 << 7;
 
             /* Return the device information word */
-            EmulatorClearFlag(EMULATOR_FLAG_CF);
-            EmulatorSetRegister(EMULATOR_REG_DX, InfoWord);
-
-            break;
+            setDX(InfoWord);
+            return TRUE;
         }
 
         /* Unsupported control code */
@@ -950,201 +1401,469 @@ VOID DosHandleIoctl(BYTE ControlCode, WORD FileHandle)
         {
             DPRINT1("Unsupported IOCTL: 0x%02X\n", ControlCode);
 
-            EmulatorSetFlag(EMULATOR_FLAG_CF);
-            EmulatorSetRegister(EMULATOR_REG_AX, ERROR_INVALID_PARAMETER);
+            DosLastError = ERROR_INVALID_PARAMETER;
+            return FALSE;
+        }
+    }
+}
+
+VOID WINAPI DosSystemBop(LPWORD Stack)
+{
+    /* Get the Function Number and skip it */
+    BYTE FuncNum = *(PBYTE)SEG_OFF_TO_PTR(getCS(), getIP());
+    setIP(getIP() + 1);
+
+    DPRINT1("Unknown DOS System BOP Function: 0x%02X\n", FuncNum);
+}
+
+VOID WINAPI DosCmdInterpreterBop(LPWORD Stack)
+{
+    /* Get the Function Number and skip it */
+    BYTE FuncNum = *(PBYTE)SEG_OFF_TO_PTR(getCS(), getIP());
+    setIP(getIP() + 1);
+
+    switch (FuncNum)
+    {
+        case 0x08: // Launch external command
+        {
+#define CMDLINE_LENGTH  1024
+
+            BOOL Result;
+            DWORD dwExitCode;
+
+            LPSTR Command = (LPSTR)SEG_OFF_TO_PTR(getDS(), getSI());
+            CHAR CommandLine[CMDLINE_LENGTH] = "";
+            STARTUPINFOA StartupInfo;
+            PROCESS_INFORMATION ProcessInformation;
+            DPRINT1("CMD Run Command '%s'\n", Command);
+
+            Command[strlen(Command)-1] = 0;
+            
+            strcpy(CommandLine, "cmd.exe /c ");
+            strcat(CommandLine, Command);
+
+            ZeroMemory(&StartupInfo, sizeof(StartupInfo));
+            ZeroMemory(&ProcessInformation, sizeof(ProcessInformation));
+
+            StartupInfo.cb = sizeof(StartupInfo);
+
+            DosPrintCharacter('\n');
+
+            Result = CreateProcessA(NULL,
+                                    CommandLine,
+                                    NULL,
+                                    NULL,
+                                    TRUE,
+                                    0,
+                                    NULL,
+                                    NULL,
+                                    &StartupInfo,
+                                    &ProcessInformation);
+            if (Result)
+            {
+                DPRINT1("Command '%s' launched successfully\n");
+
+                /* Wait for process termination */
+                WaitForSingleObject(ProcessInformation.hProcess, INFINITE);
+
+                /* Get the exit code */
+                GetExitCodeProcess(ProcessInformation.hProcess, &dwExitCode);
+
+                /* Close handles */
+                CloseHandle(ProcessInformation.hThread);
+                CloseHandle(ProcessInformation.hProcess);
+            }
+            else
+            {
+                DPRINT1("Failed when launched command '%s'\n");
+                dwExitCode = GetLastError();
+            }
+            
+            DosPrintCharacter('\n');
+
+            setAL((UCHAR)dwExitCode);
+
+            break;
+        }
+
+        default:
+        {
+            DPRINT1("Unknown DOS CMD Interpreter BOP Function: 0x%02X\n", FuncNum);
+            // setCF(1); // Disable, otherwise we enter an infinite loop
+            break;
         }
     }
 }
 
-VOID DosInt20h(WORD CodeSegment)
+VOID WINAPI DosInt20h(LPWORD Stack)
 {
     /* This is the exit interrupt */
-    DosTerminateProcess(CodeSegment, 0);
+    DosTerminateProcess(Stack[STACK_CS], 0);
 }
 
-VOID DosInt21h(WORD CodeSegment)
+VOID WINAPI DosInt21h(LPWORD Stack)
 {
-    INT i;
-    CHAR Character;
+    BYTE Character;
     SYSTEMTIME SystemTime;
     PCHAR String;
     PDOS_INPUT_BUFFER InputBuffer;
-    DWORD Eax = EmulatorGetRegister(EMULATOR_REG_AX);
-    DWORD Ecx = EmulatorGetRegister(EMULATOR_REG_CX);
-    DWORD Edx = EmulatorGetRegister(EMULATOR_REG_DX);
-    DWORD Ebx = EmulatorGetRegister(EMULATOR_REG_BX);
-    WORD DataSegment = EmulatorGetRegister(EMULATOR_REG_DS);
-    WORD ExtSegment = EmulatorGetRegister(EMULATOR_REG_ES);
 
     /* Check the value in the AH register */
-    switch (HIBYTE(Eax))
+    switch (getAH())
     {
         /* Terminate Program */
         case 0x00:
         {
-            DosTerminateProcess(CodeSegment, 0);
+            DosTerminateProcess(Stack[STACK_CS], 0);
             break;
         }
 
-        /* Read Character And Echo */
+        /* Read Character from STDIN with Echo */
         case 0x01:
         {
             Character = DosReadCharacter();
             DosPrintCharacter(Character);
-            EmulatorSetRegister(EMULATOR_REG_AX, (Eax & 0xFFFFFF00) | Character);
+
+            /* Let the BOP repeat if needed */
+            if (getCF()) break;
+
+            setAL(Character);
             break;
         }
 
-        /* Print Character */
+        /* Write Character to STDOUT */
         case 0x02:
         {
-            DosPrintCharacter(LOBYTE(Edx));
+            Character = getDL();
+            DosPrintCharacter(Character);
+
+            /*
+             * We return the output character (DOS 2.1+).
+             * Also, if we're going to output a TAB, then
+             * don't return a TAB but a SPACE instead.
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2554.htm
+             * for more information.
+             */
+            setAL(Character == '\t' ? ' ' : Character);
             break;
         }
 
-        /* Read Character Without Echo */
-        case 0x07:
-        case 0x08:
+        /* Read Character from STDAUX */
+        case 0x03:
         {
-            EmulatorSetRegister(EMULATOR_REG_AX,
-                               (Eax & 0xFFFFFF00) | DosReadCharacter());
+            // FIXME: Really read it from STDAUX!
+            DPRINT1("INT 16h, 03h: Read character from STDAUX is HALFPLEMENTED\n");
+            setAL(DosReadCharacter());
             break;
         }
 
-        /* Print String */
-        case 0x09:
+        /* Write Character to STDAUX */
+        case 0x04:
         {
-            String = (PCHAR)((ULONG_PTR)BaseAddress
-                     + TO_LINEAR(DataSegment, LOWORD(Edx)));
-
-            while ((*String) != '$')
-            {
-                DosPrintCharacter(*String);
-                String++;
-            }
-
+            // FIXME: Really write it to STDAUX!
+            DPRINT1("INT 16h, 04h: Write character to STDAUX is HALFPLEMENTED\n");
+            DosPrintCharacter(getDL());
             break;
         }
 
-        /* Read Buffered Input */
+        /* Write Character to Printer */
+        case 0x05:
+        {
+            // FIXME: Really write it to printer!
+            DPRINT1("INT 16h, 05h: Write character to printer is HALFPLEMENTED -\n\n");
+            DPRINT1("0x%p\n", getDL());
+            DPRINT1("\n\n-----------\n\n");
+            break;
+        }
+
+        /* Direct Console I/O */
+        case 0x06:
+        {
+            Character = getDL();
+
+            if (Character != 0xFF)
+            {
+                /* Output */
+                DosPrintCharacter(Character);
+
+                /*
+                 * We return the output character (DOS 2.1+).
+                 * See Ralf Brown: http://www.ctyme.com/intr/rb-2558.htm
+                 * for more information.
+                 */
+                setAL(Character);
+            }
+            else
+            {
+                /* Input */
+                if (DosCheckInput())
+                {
+                    Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_ZF;
+                    setAL(DosReadCharacter());
+                }
+                else
+                {
+                    /* No character available */
+                    Stack[STACK_FLAGS] |= EMULATOR_FLAG_ZF;
+                    setAL(0x00);
+                }
+            }
+
+            break;
+        }
+
+        /* Character Input without Echo */
+        case 0x07:
+        case 0x08:
+        {
+            Character = DosReadCharacter();
+
+            /* Let the BOP repeat if needed */
+            if (getCF()) break;
+
+            setAL(Character);
+            break;
+        }
+
+        /* Write string to STDOUT */
+        case 0x09:
+        {
+            String = (PCHAR)SEG_OFF_TO_PTR(getDS(), getDX());
+
+            while (*String != '$')
+            {
+                DosPrintCharacter(*String);
+                String++;
+            }
+
+            /*
+             * We return the terminating character (DOS 2.1+).
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2562.htm
+             * for more information.
+             */
+            setAL('$');
+            break;
+        }
+
+        /* Read Buffered Input */
         case 0x0A:
         {
-            InputBuffer = (PDOS_INPUT_BUFFER)((ULONG_PTR)BaseAddress
-                                              + TO_LINEAR(DataSegment,
-                                                          LOWORD(Edx)));
+            InputBuffer = (PDOS_INPUT_BUFFER)SEG_OFF_TO_PTR(getDS(), getDX());
 
-            InputBuffer->Length = 0;
-            for (i = 0; i < InputBuffer->MaxLength; i ++)
+            while (Stack[STACK_COUNTER] < InputBuffer->MaxLength)
             {
+                /* Try to read a character */
                 Character = DosReadCharacter();
+
+                /* If it's not ready yet, let the BOP repeat */
+                if (getCF()) break;
+
+                /* Echo the character and append it to the buffer */
                 DosPrintCharacter(Character);
-                InputBuffer->Buffer[InputBuffer->Length] = Character;
+                InputBuffer->Buffer[Stack[STACK_COUNTER]] = Character;
+
                 if (Character == '\r') break;
-                InputBuffer->Length++;
+                Stack[STACK_COUNTER]++;
+            }
+
+            /* Update the length */
+            InputBuffer->Length = Stack[STACK_COUNTER];
+            break;
+        }
+
+        /* Get STDIN Status */
+        case 0x0B:
+        {
+            setAL(DosCheckInput() ? 0xFF : 0x00);
+            break;
+        }
+
+        /* Flush Buffer and Read STDIN */
+        case 0x0C:
+        {
+            BYTE InputFunction = getAL();
+
+            /* Flush STDIN buffer */
+            DosFlushFileBuffers(DOS_INPUT_HANDLE); // Maybe just create a DosFlushInputBuffer...
+
+            /*
+             * If the input function number contained in AL is valid, i.e.
+             * AL == 0x01 or 0x06 or 0x07 or 0x08 or 0x0A, call ourselves
+             * recursively with AL == AH.
+             */
+            if (InputFunction == 0x01 || InputFunction == 0x06 ||
+                InputFunction == 0x07 || InputFunction == 0x08 ||
+                InputFunction == 0x0A)
+            {
+                setAH(InputFunction);
+                /*
+                 * Instead of calling ourselves really recursively as in:
+                 * DosInt21h(Stack);
+                 * prefer resetting the CF flag to let the BOP repeat.
+                 */
+                setCF(1);
             }
+            break;
+        }
 
+        /* Disk Reset */
+        case 0x0D:
+        {
+            PDOS_PSP PspBlock = SEGMENT_TO_PSP(CurrentPsp);
+
+            // TODO: Flush what's needed.
+            DPRINT1("INT 21h, 0Dh is UNIMPLEMENTED\n");
+
+            /* Clear CF in DOS 6 only */
+            if (PspBlock->DosVersion == 0x0006)
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+
+            break;
+        }
+
+        /* Set Default Drive  */
+        case 0x0E:
+        {
+            DosChangeDrive(getDL());
+            setAL(LastDrive - 'A' + 1);
+            break;
+        }
+
+        /* NULL Function for CP/M Compatibility */
+        case 0x18:
+        {
+            /*
+             * This function corresponds to the CP/M BDOS function
+             * "get bit map of logged drives", which is meaningless
+             * under MS-DOS.
+             *
+             * For: PTS-DOS 6.51 & S/DOS 1.0 - EXTENDED RENAME FILE USING FCB
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2584.htm
+             * for more information.
+             */
+            setAL(0x00);
+            break;
+        }
+
+        /* Get Default Drive */
+        case 0x19:
+        {
+            setAL(CurrentDrive);
             break;
         }
 
         /* Set Disk Transfer Area */
         case 0x1A:
         {
-            DiskTransferArea = MAKELONG(LOWORD(Edx), DataSegment);
+            DiskTransferArea = MAKELONG(getDX(), getDS());
+            break;
+        }
+
+        /* NULL Function for CP/M Compatibility */
+        case 0x1D:
+        case 0x1E:
+        {
+            /*
+             * Function 0x1D corresponds to the CP/M BDOS function
+             * "get bit map of read-only drives", which is meaningless
+             * under MS-DOS.
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2592.htm
+             * for more information.
+             *
+             * Function 0x1E corresponds to the CP/M BDOS function
+             * "set file attributes", which was meaningless under MS-DOS 1.x.
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2593.htm
+             * for more information.
+             */
+            setAL(0x00);
+            break;
+        }
+
+        /* NULL Function for CP/M Compatibility */
+        case 0x20:
+        {
+            /*
+             * This function corresponds to the CP/M BDOS function
+             * "get/set default user (sublibrary) number", which is meaningless
+             * under MS-DOS.
+             *
+             * For: S/DOS 1.0+ & PTS-DOS 6.51+ - GET OEM REVISION
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2596.htm
+             * for more information.
+             */
+            setAL(0x00);
             break;
         }
 
         /* Set Interrupt Vector */
         case 0x25:
         {
-            DWORD FarPointer = MAKELONG(LOWORD(Edx), DataSegment);
+            DWORD FarPointer = MAKELONG(getDX(), getDS());
+            DPRINT1("Setting interrupt 0x%x ...\n", getAL());
 
             /* Write the new far pointer to the IDT */
-            ((PDWORD)BaseAddress)[LOBYTE(Eax)] = FarPointer;
+            ((PDWORD)BaseAddress)[getAL()] = FarPointer;
+            break;
+        }
 
+        /* Create New PSP */
+        case 0x26:
+        {
+            DPRINT1("INT 21h, 26h - Create New PSP is UNIMPLEMENTED\n");
             break;
         }
 
-        /* Get system date */
+        /* Get System Date */
         case 0x2A:
         {
             GetLocalTime(&SystemTime);
-            EmulatorSetRegister(EMULATOR_REG_CX,
-                                (Ecx & 0xFFFF0000) | SystemTime.wYear);
-            EmulatorSetRegister(EMULATOR_REG_DX,
-                                (Edx & 0xFFFF0000)
-                                | (SystemTime.wMonth << 8)
-                                | SystemTime.wDay);
-            EmulatorSetRegister(EMULATOR_REG_AX,
-                                (Eax & 0xFFFFFF00) | SystemTime.wDayOfWeek);
+            setCX(SystemTime.wYear);
+            setDX(MAKEWORD(SystemTime.wDay, SystemTime.wMonth));
+            setAL(SystemTime.wDayOfWeek);
             break;
         }
 
-        /* Set system date */
+        /* Set System Date */
         case 0x2B:
         {
             GetLocalTime(&SystemTime);
-            SystemTime.wYear = LOWORD(Ecx);
-            SystemTime.wMonth = HIBYTE(Edx);
-            SystemTime.wDay = LOBYTE(Edx);
-
-            if (SetLocalTime(&SystemTime))
-            {
-                /* Return success */
-                EmulatorSetRegister(EMULATOR_REG_AX, Eax & 0xFFFFFF00);
-            }
-            else
-            {
-                /* Return failure */
-                EmulatorSetRegister(EMULATOR_REG_AX, Eax | 0xFF);
-            }
+            SystemTime.wYear  = getCX();
+            SystemTime.wMonth = getDH();
+            SystemTime.wDay   = getDL();
 
+            /* Return success or failure */
+            setAL(SetLocalTime(&SystemTime) ? 0x00 : 0xFF);
             break;
         }
 
-        /* Get system time */
+        /* Get System Time */
         case 0x2C:
         {
             GetLocalTime(&SystemTime);
-            EmulatorSetRegister(EMULATOR_REG_CX,
-                                (Ecx & 0xFFFF0000)
-                                | (SystemTime.wHour << 8)
-                                | SystemTime.wMinute);
-            EmulatorSetRegister(EMULATOR_REG_DX,
-                                (Edx & 0xFFFF0000)
-                                | (SystemTime.wSecond << 8)
-                                | (SystemTime.wMilliseconds / 10));
+            setCX(MAKEWORD(SystemTime.wMinute, SystemTime.wHour));
+            setDX(MAKEWORD(SystemTime.wMilliseconds / 10, SystemTime.wSecond));
             break;
         }
 
-        /* Set system time */
+        /* Set System Time */
         case 0x2D:
         {
             GetLocalTime(&SystemTime);
-            SystemTime.wHour = HIBYTE(Ecx);
-            SystemTime.wMinute = LOBYTE(Ecx);
-            SystemTime.wSecond = HIBYTE(Edx);
-            SystemTime.wMilliseconds = LOBYTE(Edx) * 10;
-
-            if (SetLocalTime(&SystemTime))
-            {
-                /* Return success */
-                EmulatorSetRegister(EMULATOR_REG_AX, Eax & 0xFFFFFF00);
-            }
-            else
-            {
-                /* Return failure */
-                EmulatorSetRegister(EMULATOR_REG_AX, Eax | 0xFF);
-            }
+            SystemTime.wHour         = getCH();
+            SystemTime.wMinute       = getCL();
+            SystemTime.wSecond       = getDH();
+            SystemTime.wMilliseconds = getDL() * 10; // In hundredths of seconds
 
+            /* Return success or failure */
+            setAL(SetLocalTime(&SystemTime) ? 0x00 : 0xFF);
             break;
         }
 
         /* Get Disk Transfer Area */
         case 0x2F:
         {
-            EmulatorSetRegister(EMULATOR_REG_ES, HIWORD(DiskTransferArea));
-            EmulatorSetRegister(EMULATOR_REG_BX, LOWORD(DiskTransferArea));
-
+            setES(HIWORD(DiskTransferArea));
+            setBX(LOWORD(DiskTransferArea));
             break;
         }
 
@@ -1153,18 +1872,141 @@ VOID DosInt21h(WORD CodeSegment)
         {
             PDOS_PSP PspBlock = SEGMENT_TO_PSP(CurrentPsp);
 
-            EmulatorSetRegister(EMULATOR_REG_AX, PspBlock->DosVersion);
+            /*
+             * DOS 2+ - GET DOS VERSION
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2711.htm
+             * for more information.
+             */
+
+            if (LOBYTE(PspBlock->DosVersion) < 5 || getAL() == 0x00)
+            {
+                /*
+                 * Return DOS OEM number:
+                 * 0x00 for IBM PC-DOS
+                 * 0x02 for packaged MS-DOS
+                 */
+                setBH(0x02);
+            }
+
+            if (LOBYTE(PspBlock->DosVersion) >= 5 && getAL() == 0x01)
+            {
+                /*
+                 * Return version flag:
+                 * 1 << 3 if DOS is in ROM,
+                 * 0 (reserved) if not.
+                 */
+                setBH(0x00);
+            }
+
+            /* Return DOS 24-bit user serial number in BL:CX */
+            setBL(0x00);
+            setCX(0x0000);
+
+            /*
+             * Return DOS version: Minor:Major in AH:AL
+             * The Windows NT DOS box returns version 5.00, subject to SETVER.
+             */
+            setAX(PspBlock->DosVersion);
+
+            break;
+        }
+
+        /* Extended functionalities */
+        case 0x33:
+        {
+            if (getAL() == 0x06)
+            {
+                /*
+                 * DOS 5+ - GET TRUE VERSION NUMBER
+                 * This function always returns the true version number, unlike
+                 * AH=30h, whose return value may be changed with SETVER.
+                 * See Ralf Brown: http://www.ctyme.com/intr/rb-2730.htm
+                 * for more information.
+                 */
+
+                /*
+                 * Return the true DOS version: Minor:Major in BH:BL
+                 * The Windows NT DOS box returns BX=3205h (version 5.50).
+                 */
+                setBX(NTDOS_VERSION);
+
+                /* DOS revision 0 */
+                setDL(0x00);
+
+                /* Unpatched DOS */
+                setDH(0x00);
+            }
+            // else
+            // {
+                // /* Invalid subfunction */
+                // setAL(0xFF);
+            // }
+
             break;
         }
 
         /* Get Interrupt Vector */
         case 0x35:
         {
-            DWORD FarPointer = ((PDWORD)BaseAddress)[LOBYTE(Eax)];
+            DWORD FarPointer = ((PDWORD)BaseAddress)[getAL()];
 
             /* Read the address from the IDT into ES:BX */
-            EmulatorSetRegister(EMULATOR_REG_ES, HIWORD(FarPointer));
-            EmulatorSetRegister(EMULATOR_REG_BX, LOWORD(FarPointer));
+            setES(HIWORD(FarPointer));
+            setBX(LOWORD(FarPointer));
+            break;
+        }
+
+        /* SWITCH character - AVAILDEV */
+        case 0x37:
+        {
+            if (getAL() == 0x00)
+            {
+                /*
+                 * DOS 2+ - "SWITCHAR" - GET SWITCH CHARACTER
+                 * This setting is ignored by MS-DOS 4.0+.
+                 * MS-DOS 5+ always return AL=00h/DL=2Fh.
+                 * See Ralf Brown: http://www.ctyme.com/intr/rb-2752.htm
+                 * for more information.
+                 */
+                setDL('/');
+                setAL(0x00);
+            }
+            else if (getAL() == 0x01)
+            {
+                /*
+                 * DOS 2+ - "SWITCHAR" - SET SWITCH CHARACTER
+                 * This setting is ignored by MS-DOS 5+.
+                 * See Ralf Brown: http://www.ctyme.com/intr/rb-2753.htm
+                 * for more information.
+                 */
+                // getDL();
+                setAL(0xFF);
+            }
+            else if (getAL() == 0x02)
+            {
+                /*
+                 * DOS 2.x and 3.3+ only - "AVAILDEV" - SPECIFY \DEV\ PREFIX USE
+                 * See Ralf Brown: http://www.ctyme.com/intr/rb-2754.htm
+                 * for more information.
+                 */
+                // setDL();
+                setAL(0xFF);
+            }
+            else if (getAL() == 0x03)
+            {
+                /*
+                 * DOS 2.x and 3.3+ only - "AVAILDEV" - SPECIFY \DEV\ PREFIX USE
+                 * See Ralf Brown: http://www.ctyme.com/intr/rb-2754.htm
+                 * for more information.
+                 */
+                // getDL();
+                setAL(0xFF);
+            }
+            else
+            {
+                /* Invalid subfunction */
+                setAL(0xFF);
+            }
 
             break;
         }
@@ -1172,18 +2014,16 @@ VOID DosInt21h(WORD CodeSegment)
         /* Create Directory */
         case 0x39:
         {
-            String = (PCHAR)((ULONG_PTR)BaseAddress
-                     + TO_LINEAR(DataSegment, LOWORD(Edx)));
+            String = (PCHAR)SEG_OFF_TO_PTR(getDS(), getDX());
 
             if (CreateDirectoryA(String, NULL))
             {
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
             }
             else
             {
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | LOWORD(GetLastError()));
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(LOWORD(GetLastError()));
             }
 
             break;
@@ -1192,39 +2032,34 @@ VOID DosInt21h(WORD CodeSegment)
         /* Remove Directory */
         case 0x3A:
         {
-            String = (PCHAR)((ULONG_PTR)BaseAddress
-                     + TO_LINEAR(DataSegment, LOWORD(Edx)));
+            String = (PCHAR)SEG_OFF_TO_PTR(getDS(), getDX());
 
             if (RemoveDirectoryA(String))
             {
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
             }
             else
             {
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | LOWORD(GetLastError()));
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(LOWORD(GetLastError()));
             }
 
-
             break;
         }
 
         /* Set Current Directory */
         case 0x3B:
         {
-            String = (PCHAR)((ULONG_PTR)BaseAddress
-                     + TO_LINEAR(DataSegment, LOWORD(Edx)));
+            String = (PCHAR)SEG_OFF_TO_PTR(getDS(), getDX());
 
-            if (SetCurrentDirectoryA(String))
+            if (DosChangeDirectory(String))
             {
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
             }
             else
             {
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | LOWORD(GetLastError()));
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(DosLastError);
             }
 
             break;
@@ -1235,27 +2070,18 @@ VOID DosInt21h(WORD CodeSegment)
         {
             WORD FileHandle;
             WORD ErrorCode = DosCreateFile(&FileHandle,
-                                           (LPCSTR)(ULONG_PTR)BaseAddress
-                                           + TO_LINEAR(DataSegment, LOWORD(Edx)),
-                                           LOWORD(Ecx));
+                                           (LPCSTR)SEG_OFF_TO_PTR(getDS(), getDX()),
+                                           getCX());
 
             if (ErrorCode == 0)
             {
-                /* Clear CF */
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
-
-                /* Return the handle in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | FileHandle);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAX(FileHandle);
             }
             else
             {
-                /* Set CF */
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
-
-                /* Return the error code in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | ErrorCode);
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ErrorCode);
             }
 
             break;
@@ -1265,28 +2091,19 @@ VOID DosInt21h(WORD CodeSegment)
         case 0x3D:
         {
             WORD FileHandle;
-            WORD ErrorCode = DosCreateFile(&FileHandle,
-                                           (LPCSTR)(ULONG_PTR)BaseAddress
-                                           + TO_LINEAR(DataSegment, LOWORD(Edx)),
-                                           LOBYTE(Eax));
+            WORD ErrorCode = DosOpenFile(&FileHandle,
+                                         (LPCSTR)SEG_OFF_TO_PTR(getDS(), getDX()),
+                                         getAL());
 
             if (ErrorCode == 0)
             {
-                /* Clear CF */
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
-
-                /* Return the handle in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | FileHandle);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAX(FileHandle);
             }
             else
             {
-                /* Set CF */
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
-
-                /* Return the error code in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | ErrorCode);
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ErrorCode);
             }
 
             break;
@@ -1295,82 +2112,191 @@ VOID DosInt21h(WORD CodeSegment)
         /* Close File */
         case 0x3E:
         {
-            if (DosCloseHandle(LOWORD(Ebx)))
+            if (DosCloseHandle(getBX()))
             {
-                /* Clear CF */
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
             }
             else
             {
-                /* Set CF */
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
-
-                /* Return the error code in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | ERROR_INVALID_PARAMETER);
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_INVALID_HANDLE);
             }
 
             break;
         }
 
-        /* Read File */
+        /* Read from File or Device */
         case 0x3F:
         {
+            WORD Handle    = getBX();
+            LPBYTE Buffer  = (LPBYTE)SEG_OFF_TO_PTR(getDS(), getDX());
+            WORD Count     = getCX();
             WORD BytesRead = 0;
-            WORD ErrorCode = DosReadFile(LOWORD(Ebx),
-                                         (LPVOID)((ULONG_PTR)BaseAddress
-                                         + TO_LINEAR(DataSegment, LOWORD(Edx))),
-                                         LOWORD(Ecx),
-                                         &BytesRead);
+            WORD ErrorCode = ERROR_SUCCESS;
+            CHAR Character;
 
-            if (ErrorCode == 0)
+            if (IsConsoleHandle(DosGetRealHandle(Handle)))
             {
-                /* Clear CF */
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
-
-                /* Return the number of bytes read in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | BytesRead);
+                while (Stack[STACK_COUNTER] < Count)
+                {
+                    /* Read a character from the BIOS */
+                    Character = LOBYTE(BiosGetCharacter());
+
+                    /* Stop if the BOP needs to be repeated */
+                    if (getCF()) break;
+
+                    // FIXME: Security checks!
+                    DosPrintCharacter(Character);
+                    Buffer[Stack[STACK_COUNTER]++] = Character;
+
+                    if (Character == '\r')
+                    {
+                        /* Stop on first carriage return */
+                        DosPrintCharacter('\n');
+                        break;
+                    }
+                }
+
+                if (Character != '\r')
+                {
+                    if (Stack[STACK_COUNTER] < Count) ErrorCode = ERROR_NOT_READY;
+                    else BytesRead = Count;
+                }
+                else BytesRead = Stack[STACK_COUNTER];
             }
             else
             {
-                /* Set CF */
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
+                /* Use the file reading function */
+                ErrorCode = DosReadFile(Handle, Buffer, Count, &BytesRead);
+            }
 
-                /* Return the error code in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | ErrorCode);
+            if (ErrorCode == ERROR_SUCCESS)
+            {
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAX(BytesRead);
+            }
+            else if (ErrorCode != ERROR_NOT_READY)
+            {
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ErrorCode);
             }
             break;
         }
 
-        /* Write File */
+        /* Write to File or Device */
         case 0x40:
         {
             WORD BytesWritten = 0;
-            WORD ErrorCode = DosWriteFile(LOWORD(Ebx),
-                                          (LPVOID)((ULONG_PTR)BaseAddress
-                                          + TO_LINEAR(DataSegment, LOWORD(Edx))),
-                                          LOWORD(Ecx),
+            WORD ErrorCode = DosWriteFile(getBX(),
+                                          SEG_OFF_TO_PTR(getDS(), getDX()),
+                                          getCX(),
                                           &BytesWritten);
 
-            if (ErrorCode == 0)
+            if (ErrorCode == ERROR_SUCCESS)
+            {
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAX(BytesWritten);
+            }
+            else
+            {
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ErrorCode);
+            }
+
+            break;
+        }
+
+        /* Delete File */
+        case 0x41:
+        {
+            LPSTR FileName = (LPSTR)SEG_OFF_TO_PTR(getDS(), getDX());
+
+            /* Call the API function */
+            if (DeleteFileA(FileName))
+            {
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                /*
+                 * See Ralf Brown: http://www.ctyme.com/intr/rb-2797.htm
+                 * "AX destroyed (DOS 3.3) AL seems to be drive of deleted file."
+                 */
+                setAL(FileName[0] - 'A');
+            }
+            else
+            {
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(GetLastError());
+            }
+
+            break;
+        }
+
+        /* Seek File */
+        case 0x42:
+        {
+            DWORD NewLocation;
+            WORD ErrorCode = DosSeekFile(getBX(),
+                                         MAKELONG(getDX(), getCX()),
+                                         getAL(),
+                                         &NewLocation);
+
+            if (ErrorCode == ERROR_SUCCESS)
             {
-                /* Clear CF */
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
 
-                /* Return the number of bytes written in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | BytesWritten);
+                /* Return the new offset in DX:AX */
+                setDX(HIWORD(NewLocation));
+                setAX(LOWORD(NewLocation));
             }
             else
             {
-                /* Set CF */
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ErrorCode);
+            }
+
+            break;
+        }
+
+        /* Get/Set File Attributes */
+        case 0x43:
+        {
+            DWORD Attributes;
+            LPSTR FileName = (LPSTR)SEG_OFF_TO_PTR(getDS(), getDX());
 
-                /* Return the error code in AX */
-                EmulatorSetRegister(EMULATOR_REG_AX,
-                                    (Eax & 0xFFFF0000) | ErrorCode);
+            if (getAL() == 0x00)
+            {
+                /* Get the attributes */
+                Attributes = GetFileAttributesA(FileName);
+
+                /* Check if it failed */
+                if (Attributes == INVALID_FILE_ATTRIBUTES)
+                {
+                    Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                    setAX(GetLastError());
+                }
+                else
+                {
+                    /* Return the attributes that DOS can understand */
+                    Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                    setCX(Attributes & 0x00FF);
+                }
+            }
+            else if (getAL() == 0x01)
+            {
+                /* Try to set the attributes */
+                if (SetFileAttributesA(FileName, getCL()))
+                {
+                    Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                }
+                else
+                {
+                    Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                    setAX(GetLastError());
+                }
+            }
+            else
+            {
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_INVALID_FUNCTION);
             }
 
             break;
@@ -1379,7 +2305,98 @@ VOID DosInt21h(WORD CodeSegment)
         /* IOCTL */
         case 0x44:
         {
-            DosHandleIoctl(LOBYTE(Eax), LOWORD(Ebx));
+            if (DosHandleIoctl(getAL(), getBX()))
+            {
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+            }
+            else
+            {
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(DosLastError);
+            }
+
+            break;
+        }
+
+        /* Duplicate Handle */
+        case 0x45:
+        {
+            WORD NewHandle;
+            HANDLE Handle = DosGetRealHandle(getBX());
+
+            if (Handle != INVALID_HANDLE_VALUE)
+            {
+                /* The handle is invalid */
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_INVALID_HANDLE);
+                break;
+            }
+
+            /* Open a new handle to the same entry */
+            NewHandle = DosOpenHandle(Handle);
+
+            if (NewHandle == INVALID_DOS_HANDLE)
+            {
+                /* Too many files open */
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_TOO_MANY_OPEN_FILES);
+                break;
+            }
+
+            /* Return the result */
+            Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+            setAX(NewHandle);
+            break;
+        }
+
+        /* Force Duplicate Handle */
+        case 0x46:
+        {
+            if (DosDuplicateHandle(getBX(), getCX()))
+            {
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+            }
+            else
+            {
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_INVALID_HANDLE);
+            }
+
+            break;
+        }
+
+        /* Get Current Directory */
+        case 0x47:
+        {
+            BYTE DriveNumber = getDL();
+            String = (PCHAR)SEG_OFF_TO_PTR(getDS(), getSI());
+
+            /* Get the real drive number */
+            if (DriveNumber == 0)
+            {
+                DriveNumber = CurrentDrive;
+            }
+            else
+            {
+                /* Decrement DriveNumber since it was 1-based */
+                DriveNumber--;
+            }
+
+            if (DriveNumber <= LastDrive - 'A')
+            {
+                /*
+                 * Copy the current directory into the target buffer.
+                 * It doesn't contain the drive letter and the backslash.
+                 */
+                strncpy(String, CurrentDirectories[DriveNumber], DOS_DIR_LENGTH);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAX(0x0100); // Undocumented, see Ralf Brown: http://www.ctyme.com/intr/rb-2933.htm
+            }
+            else
+            {
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_INVALID_DRIVE);
+            }
 
             break;
         }
@@ -1388,18 +2405,18 @@ VOID DosInt21h(WORD CodeSegment)
         case 0x48:
         {
             WORD MaxAvailable = 0;
-            WORD Segment = DosAllocateMemory(LOWORD(Ebx), &MaxAvailable);
+            WORD Segment = DosAllocateMemory(getBX(), &MaxAvailable);
 
             if (Segment != 0)
             {
-                EmulatorSetRegister(EMULATOR_REG_AX, Segment);
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAX(Segment);
             }
             else
             {
-                EmulatorSetRegister(EMULATOR_REG_AX, ERROR_NOT_ENOUGH_MEMORY);
-                EmulatorSetRegister(EMULATOR_REG_BX, MaxAvailable);
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(DosLastError);
+                setBX(MaxAvailable);
             }
 
             break;
@@ -1408,11 +2425,15 @@ VOID DosInt21h(WORD CodeSegment)
         /* Free Memory */
         case 0x49:
         {
-            if (DosFreeMemory(ExtSegment))
+            if (DosFreeMemory(getES()))
+            {
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+            }
+            else
             {
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_ARENA_TRASHED);
             }
-            else EmulatorSetFlag(EMULATOR_FLAG_CF);
 
             break;
         }
@@ -1422,14 +2443,15 @@ VOID DosInt21h(WORD CodeSegment)
         {
             WORD Size;
 
-            if (DosResizeMemory(ExtSegment, LOWORD(Ebx), &Size))
+            if (DosResizeMemory(getES(), getBX(), &Size))
             {
-                EmulatorClearFlag(EMULATOR_FLAG_CF);
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
             }
             else
             {
-                EmulatorSetFlag(EMULATOR_FLAG_CF);
-                EmulatorSetRegister(EMULATOR_REG_BX, Size);
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(DosLastError);
+                setBX(Size);
             }
 
             break;
@@ -1438,25 +2460,147 @@ VOID DosInt21h(WORD CodeSegment)
         /* Terminate With Return Code */
         case 0x4C:
         {
-            DosTerminateProcess(CurrentPsp, LOBYTE(Eax));
+            DosTerminateProcess(CurrentPsp, getAL());
+            break;
+        }
+
+        /* Get Return Code (ERRORLEVEL) */
+        case 0x4D:
+        {
+            /*
+             * According to Ralf Brown: http://www.ctyme.com/intr/rb-2976.htm
+             * DosErrorLevel is cleared after being read by this function.
+             */
+            Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+            setAX(DosErrorLevel);
+            DosErrorLevel = 0x0000; // Clear it
+            break;
+        }
+
+        /* Internal - Set Current Process ID (Set PSP Address) */
+        case 0x50:
+        {
+            // FIXME: Is it really what it's done ??
+            CurrentPsp = getBX();
+            break;
+        }
+
+        /* Internal - Get Current Process ID (Get PSP Address) */
+        case 0x51:
+        /* Get Current PSP Address */
+        case 0x62:
+        {
+            /*
+             * Undocumented AH=51h is identical to the documented AH=62h.
+             * See Ralf Brown: http://www.ctyme.com/intr/rb-2982.htm
+             * and http://www.ctyme.com/intr/rb-3140.htm
+             * for more information.
+             */
+            setBX(CurrentPsp);
+            break;
+        }
+
+        /* Get/Set Memory Management Options */
+        case 0x58:
+        {
+            if (getAL() == 0x00)
+            {
+                /* Get allocation strategy */
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAX(DosAllocStrategy);
+            }
+            else if (getAL() == 0x01)
+            {
+                /* Set allocation strategy */
+
+                if ((getBL() & (DOS_ALLOC_HIGH | DOS_ALLOC_HIGH_LOW))
+                    == (DOS_ALLOC_HIGH | DOS_ALLOC_HIGH_LOW))
+                {
+                    /* Can't set both */
+                    Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                    setAX(ERROR_INVALID_PARAMETER);
+                    break;
+                }
+
+                if ((getBL() & 0x3F) > DOS_ALLOC_LAST_FIT)
+                {
+                    /* Invalid allocation strategy */
+                    Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                    setAX(ERROR_INVALID_PARAMETER);
+                    break;
+                }
+
+                DosAllocStrategy = getBL();
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+            }
+            else if (getAL() == 0x02)
+            {
+                /* Get UMB link state */
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+                setAL(DosUmbLinked ? 0x01 : 0x00);
+            }
+            else if (getAL() == 0x03)
+            {
+                /* Set UMB link state */
+                if (getBX()) DosLinkUmb();
+                else DosUnlinkUmb();
+                Stack[STACK_FLAGS] &= ~EMULATOR_FLAG_CF;
+            }
+            else
+            {
+                /* Invalid or unsupported function */
+                Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+                setAX(ERROR_INVALID_FUNCTION);
+            }
+
             break;
         }
 
         /* Unsupported */
         default:
         {
-            DPRINT1("DOS Function INT 0x21, AH = 0x%02X NOT IMPLEMENTED!\n", HIBYTE(Eax));
-            EmulatorSetFlag(EMULATOR_FLAG_CF);
+            DPRINT1("DOS Function INT 0x21, AH = %xh, AL = %xh NOT IMPLEMENTED!\n",
+                    getAH(), getAL());
+
+            setAL(0); // Some functions expect AL to be 0 when it's not supported.
+            Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
         }
     }
 }
 
-VOID DosBreakInterrupt()
+VOID WINAPI DosBreakInterrupt(LPWORD Stack)
 {
+    UNREFERENCED_PARAMETER(Stack);
+
     VdmRunning = FALSE;
 }
 
-BOOLEAN DosInitialize()
+VOID WINAPI DosFastConOut(LPWORD Stack)
+{
+    /*
+     * This is the DOS 2+ Fast Console Output Interrupt.
+     * See Ralf Brown: http://www.ctyme.com/intr/rb-4124.htm
+     * for more information.
+     */
+    UNREFERENCED_PARAMETER(Stack);
+
+    /*
+     * The default handler under DOS 2.x and 3.x simply calls INT 10/AH=0Eh.
+     * Do better and call directly BiosPrintCharacter: it's what INT 10/AH=0Eh
+     * does. Otherwise we would have to set BL to DOS_CHAR_ATTRIBUTE and
+     * BH to Bda->VideoPage.
+     */
+    BiosPrintCharacter(getAL(), DOS_CHAR_ATTRIBUTE, Bda->VideoPage);
+}
+
+VOID WINAPI DosInt2Fh(LPWORD Stack)
+{
+    DPRINT1("DOS System Function INT 0x2F, AH = %xh, AL = %xh NOT IMPLEMENTED!\n",
+            getAH(), getAL());
+    Stack[STACK_FLAGS] |= EMULATOR_FLAG_CF;
+}
+
+BOOLEAN DosInitialize(VOID)
 {
     BYTE i;
     PDOS_MCB Mcb = SEGMENT_TO_MCB(FIRST_MCB_SEGMENT);
@@ -1464,14 +2608,29 @@ BOOLEAN DosInitialize()
     WCHAR Buffer[256];
     LPWSTR SourcePtr, Environment;
     LPSTR AsciiString;
-    LPSTR DestPtr = (LPSTR)((ULONG_PTR)BaseAddress + TO_LINEAR(SYSTEM_ENV_BLOCK, 0));
+    LPSTR DestPtr = (LPSTR)SEG_OFF_TO_PTR(SYSTEM_ENV_BLOCK, 0);
     DWORD AsciiSize;
+    CHAR CurrentDirectory[MAX_PATH];
+    CHAR DosDirectory[DOS_DIR_LENGTH];
+    LPSTR Path;
 
     /* Initialize the MCB */
     Mcb->BlockType = 'Z';
     Mcb->Size = USER_MEMORY_SIZE;
     Mcb->OwnerPsp = 0;
 
+    /* Initialize the link MCB to the UMB area */
+    Mcb = SEGMENT_TO_MCB(FIRST_MCB_SEGMENT + USER_MEMORY_SIZE + 1);
+    Mcb->BlockType = 'M';
+    Mcb->Size = UMB_START_SEGMENT - FIRST_MCB_SEGMENT - USER_MEMORY_SIZE - 2;
+    Mcb->OwnerPsp = SYSTEM_PSP;
+
+    /* Initialize the UMB area */
+    Mcb = SEGMENT_TO_MCB(UMB_START_SEGMENT);
+    Mcb->BlockType = 'Z';
+    Mcb->Size = UMB_END_SEGMENT - UMB_START_SEGMENT;
+    Mcb->OwnerPsp = 0;
+
     /* Get the environment strings */
     SourcePtr = Environment = GetEnvironmentStringsW();
     if (Environment == NULL) return FALSE;
@@ -1510,19 +2669,53 @@ BOOLEAN DosInitialize()
         /* Copy the string into DOS memory */
         strcpy(DestPtr, AsciiString);
 
-        /* Free the memory */
-        HeapFree(GetProcessHeap(), 0, AsciiString);
-
         /* Move to the next string */
         SourcePtr += wcslen(SourcePtr) + 1;
         DestPtr += strlen(AsciiString);
         *(DestPtr++) = 0;
+
+        /* Free the memory */
+        HeapFree(GetProcessHeap(), 0, AsciiString);
     }
     *DestPtr = 0;
 
     /* Free the memory allocated for environment strings */
     FreeEnvironmentStringsW(Environment);
 
+    /* Clear the current directory buffer */
+    ZeroMemory(CurrentDirectories, sizeof(CurrentDirectories));
+
+    /* Get the current directory */
+    if (!GetCurrentDirectoryA(MAX_PATH, CurrentDirectory))
+    {
+        // TODO: Use some kind of default path?
+        return FALSE;
+    }
+
+    /* Convert that to a DOS path */
+    if (!GetShortPathNameA(CurrentDirectory, DosDirectory, DOS_DIR_LENGTH))
+    {
+        // TODO: Use some kind of default path?
+        return FALSE;
+    }
+
+    /* Set the drive */
+    CurrentDrive = DosDirectory[0] - 'A';
+
+    /* Get the directory part of the path */
+    Path = strchr(DosDirectory, '\\');
+    if (Path != NULL)
+    {
+        /* Skip the backslash */
+        Path++;
+    }
+
+    /* Set the directory */
+    if (Path != NULL)
+    {
+        strncpy(CurrentDirectories[CurrentDrive], Path, DOS_DIR_LENGTH);
+    }
+
     /* Read CONFIG.SYS */
     Stream = _wfopen(DOS_CONFIG_PATH, L"r");
     if (Stream != NULL)
@@ -1546,6 +2739,19 @@ BOOLEAN DosInitialize()
     DosSystemFileTable[1] = GetStdHandle(STD_OUTPUT_HANDLE);
     DosSystemFileTable[2] = GetStdHandle(STD_ERROR_HANDLE);
 
+    /* Register the DOS BOPs */
+    RegisterBop(BOP_DOS, DosSystemBop        );
+    RegisterBop(BOP_CMD, DosCmdInterpreterBop);
+
+    /* Register the DOS 32-bit Interrupts */
+    RegisterInt32(0x20, DosInt20h        );
+    RegisterInt32(0x21, DosInt21h        );
+//  RegisterInt32(0x22, DosInt22h        ); // Termination
+    RegisterInt32(0x23, DosBreakInterrupt); // Ctrl-C / Ctrl-Break
+//  RegisterInt32(0x24, DosInt24h        ); // Critical Error
+    RegisterInt32(0x29, DosFastConOut    ); // DOS 2+ Fast Console Output
+    RegisterInt32(0x2F, DosInt2Fh        );
+
     return TRUE;
 }