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------------------------------------------------------------------------------ ---------------------- PMODE For Watcom C/C++ - v1.14 ------------------------ ------------------------------------------------------------------------------ This is the documentation for PMODE for Watcom C/C++ - v1.14, henceforth referred to as PMODE/W. PMODE/W is Copyright (c) 1994, Charles Scheffold and Thomas Pytel. All rights reserved. Contents: --------- 1 - Overview 1.0 - Legal disclaimer 1.1 - Description 1.2 - Usage 1.3 - Performance and compatibility 1.4 - PMODE/W protected mode 1.5 - PMODE/W execution 1.6 - Terms for non-commercial use 1.7 - Licensing PMODE/W for commercial use 1.8 - Contact information 2 - Supported DPMI INT 31h functions 2.0 - Function 0000h - Allocate Descriptors 2.1 - Function 0001h - Free Descriptor 2.2 - Function 0003h - Get Selector Increment Value 2.3 - Function 0006h - Get Segment Base Address 2.4 - Function 0007h - Set Segment Base Address 2.5 - Function 0008h - Set Segment Limit 2.6 - Function 0009h - Set Descriptor Access Rights 2.7 - Function 000Ah - Create Alias Descriptor 2.8 - Function 000Bh - Get Descriptor 2.9 - Function 000Ch - Set Descriptor 2.10 - Function 0100h - Allocate DOS Memory Block 2.11 - Function 0101h - Free DOS Memory Block 2.12 - Function 0102h - Resize DOS Memory Block 2.13 - Function 0200h - Get Real Mode Interrupt Vector 2.14 - Function 0201h - Set Real Mode Interrupt Vector 2.15 - Function 0204h - Get Protected Mode Interrupt Vector 2.16 - Function 0205h - Set Protected Mode Interrupt Vector 2.17 - Function 0300h - Simulate Real Mode Interrupt 2.18 - Function 0301h - Call Real Mode Procedure With Far Return Frame 2.19 - Function 0302h - Call Real Mode Procedure With IRET Frame 2.20 - Function 0303h - Allocate Real Mode Callback Address 2.21 - Function 0304h - Free Real Mode Callback Address 2.22 - Function 0305h - Get State Save/Restore Addresses 2.23 - Function 0306h - Get Raw Mode Switch Addresses 2.24 - Function 0400h - Get Version 2.25 - Function 0500h - Get Free Memory Information 2.26 - Function 0501h - Allocate Memory Block 2.27 - Function 0502h - Free Memory Block 2.28 - Function 0503h - Resize Memory Block 2.29 - Function 0800h - Physical Address Mapping 2.30 - Function 0801h - Free Physical Address Mapping 2.31 - Function 0900h - Get and Disable Virtual Interrupt State 2.32 - Function 0901h - Get and Enable Virtual Interrupt State 2.33 - Function 0902h - Get Virtual Interrupt State 3 - Supported DOS extended INT 21h functions 3.0 - Function 09h - Write String to Standard Output 3.1 - Function 1Ah - Set Disk Transfer Area 3.2 - Function 1Bh - Get Allocation Information for Default Drive 3.3 - Function 1Ch - Get Allocation Information for Specific Drive 3.4 - Function 1Fh - Get Drive Parameter Block for Default Drive 3.5 - Function 25h - Set Interrupt Vector 3.6 - Function 2Fh - Get Disk Transfer Area 3.7 - Function 32h - Get Drive Parameter Block for Specific Drive 3.8 - Function 34h - Get Address of InDOS Flag 3.9 - Function 35h - Get Interrupt Vector 3.10 - Function 39h - Create Subdirectory 3.11 - Function 3Ah - Remove Subdirectory 3.12 - Function 3Bh - Set Directory 3.13 - Function 3Ch - Create File 3.14 - Function 3Dh - Open File 3.15 - Function 3Fh - Read From File 3.16 - Function 40h - Write to File 3.17 - Function 41h - Delete File 3.18 - Function 43h - Get/Set File Attributes 3.19 - Function 47h - Get Directory Path 3.20 - Function 48h - Allocate Memory Block 3.21 - Function 49h - Free Memory Block 3.22 - Function 4Ah - Resize Memory Block 3.23 - Function 4Bh - Sub-Function 00h - Load and Execute Program 3.24 - Function 4Eh - Search for First Filename Match 3.25 - Function 4Fh - Search for Next Filename Match 3.26 - Function 56h - Rename File 4 - Supported mouse extended INT 33h functions 4.0 - Function 0009h - Define Graphics Cursor 4.1 - Function 000Ch - Define Interrupt Subroutine Parameters 4.2 - Function 0016h - Save Driver State 4.3 - Function 0017h - Restore Driver State ------------------------------------------------------------------------------ ------------------------------ 1 - Overview ---------------------------------- ------------------------------------------------------------------------------ This section will give you all the information you will need to plug PMODE/W right into your Watcom C/C++ protected mode programs. All of the other things you need to be aware of about using PMODE/W commercially and non-commercially are also in this section. Specific information on INT 31h and INT 21h DOS extended services supported by PMODE/W is in the following sections. Please note that we have only tested this extender with Watcom C/C++ versions 9.5 and 10.0. 1.0 - Legal disclaimer: ----------------------- We exclude any and all implied warranties, including warranties of merchantability and fitness for a particular purpose. We make no warranty or representation, either express or implied, with respect to PMODE/W, its quality, performance, merchantability, or fitness for a particular purpose. We shall have no liability for special, incidental, or consequential damages arising out of or resulting from the use, misuse, or modification of PMODE/W. All trademarks used in this documentation are property of their respective owners. 1.1 - Description: ------------------ PMODE/W is basically a direct replacement for DOS/4GW, the default extender for Watcom C/C++. PMODE/W itself is confined within a single small EXE file. This EXE file is what you make your stub at link time, basically replacing the DOS/4GW stub which searches the path for DOS/4GW and re-executes it on the original program. Programs linked with the PMODE/W extender do not need any big, bulky external program to execute. When a PMODE/W program is executed, the extender within the EXE does all the setup necessary and runs the protected mode portion of that EXE. A nice feature of PMODE/W programs is that you can always run them with DOS/4GW if you wish. Executing DOS/4GW on a PMODE/W program will cause the PMODE/W extender in the EXE to be ignored and DOS/4GW will basically just run the protected mode portion of the program itself. This also means you can debug PMODE/W programs just as easily by using the debugger that is part of the Watcom C/C++ package. All in all, PMODE/W gives you a great deal of flexibility. You may do all of your development with PMODE/W, but if you are unsatisfied with the performance or with any other aspect of PMODE/W, you may switch back to DOS/4GW at any time quite easily. This also applies the other way around: do all of your development with DOS/4GW, then for the release version use PMODE/W. There are other extenders available for Watcom C/C++ and they do provide a lot more 'stuff', but they do not approach PMODE/W in terms of speed and size. To be fair, we must note the disadvantages of PMODE/W. It does lack that 'stuff' which the other more professional extenders posess. The good point being it also lacks the overhead of supporting that 'stuff'. For example, PMODE/W does absolutely no exception trapping whatsoever. This is purely an ideological thing. We do not wish to slow down the IRQ process in ANY way at all. We know (since we do a lot of it) that there are applications where the lowest possible interrupt latency is required. Exception handlers would force us to slow down IRQ response (reprogramming the PICs is out of the question). However, this is not a major loss as you should not be getting exceptions in a release version of a program anyway. During development you can always run DOS/4GW on your code to provide exception trapping. To sum it up, if you are looking for a good solid, stable, and fast extender, you need look no further. If frills are what you want, PMODE/W may not be the best choice for you. Here are the advantages of PMODE/W: ) No external extender required (everything needed to execute is in the EXE). ) Small size (less than 9k for the entire extender program). ) Low memory overhead. ) Does not require ANY extended memory to load OR execute. ) No annoying initialization messages. ) Fast execution time. ) Free for non-commercial use. 1.2 - Usage: ------------ The following main files should be present in your PMODE/W archive (probably among various BBS ads and other junk): ) PMODEW.EXE - The actual PMODE/W DOS extender. ) PMODEW.DOC - The documentation you are now reading. ) PMODEW.LNK - Example linker initialization file for PMODE/W. ) MAKEEX.BAT - Batch file that builds some example programs. ) PMWSETUP.EXE - PMODE/W parameter setup program. There will also be present a few example C files. You may just run MAKEEX to build the example files and then run them for your own satisfaction. You will probably want to add a new system, PMODE/W, to your WLSYSTEM.LNK file. All you need to do in this case is add the contents of PMODEW.LNK to your WLSYSTEM.LNK file, this will add the system 'pmodew' to your Watcom C/C++ setup. You may also just compile to a 'dos4g' system but replace the stub with PMODEW.EXE. The PMWSETUP program will set up the default parameters for protected mode under PMODE/W either within the PMODEW.EXE file itself, or in any program that has been compiled with PMODE/W. These parameters will be discussed in more detail later on in this document, for now let it suffice to say that they control PMODE/W behavior in such a way that they do not need to be modified very often, usually never. If you modify the parameters in PMODEW.EXE, they will take effect in any program compiled with PMODE/W from that point on. 1.3 - Performance and compatibility: ------------------------------------ Our major concerns in developing PMODE/W were speed, size, and stability. PMODE/W itself was written entirely in assembly (unlike some extenders we know). When running under PMODE/W your code will be running at a privilege level of zero, the highest and fastest. PMODE/W does not virtualize anything, and does not invoke any protected mode mechanism that is slow. For example, if the system is running clean or under XMS, PMODE/W does not turn on paging. Under a memory manager which provides both VCPI and DPMI services, PMODE/W will opt for VCPI protected mode which is significantly faster than DPMI. When PMODE/W makes calls to real mode, it switches the system into actual real mode rather than the slower V86 mode (when it can, under VCPI this is not possible, control must be passed back to the VCPI server). In terms of speed, when your code is running under PMODE/W, it is running as fast as the system will allow. In terms of size on disk, we need say no more than for you to look at the size of the PMODE/W executable and compare it to that other extender. In terms of memory size, you may do tests yourself to confirm that PMODE/W does indeed suck up a lot less memory at run-time than the competition. In fact, PMODE/W will run even if there is absolutely no extended memory in the system (assuming of course there is enough low memory for the program). To be fair, we must say we squished the PMODE/W executable with our own compression program written expressly for the purpose (this demonstrates the extent we took most of our optimizations to). As for compatibility, PMODE/W is fully compatible with DOS/4GW as far as Watcom C/C++ is concerned. PMODE/W extends only those DOS functions required by the Watcom C/C++ libraries (though this is a good deal of them). The exception is BIOS INT 13h functions, which PMODE/W does not extend. PMODE/W also provides a subset of DPMI 0.9 INT 31h functions in protected mode. We do not emulate DOS/4GW though, as none of its API functions are duplicated by PMODE/W. PMODE/W will run under a clean system, XMS, VCPI, or DPMI. Though you should be aware that under a DPMI system, PMODE/W will not be providing the DPMI functions, but rather the actual DPMI host in the system will. You should also be aware that PMODE/W will leave the A20 line enabled when calling real mode. Disabling the A20 for real mode is not really necessary, it is a big slowdown during mode switches to have to enable/disable the A20, so PMODE/W avoids it. 1.4 - PMODE/W protected mode: ----------------------------- For those of you who are familiar with it, the PMODE/W kernel is based on the PMODE 3 kernel by Thomas Pytel that has been available in the public domain for some time now. If you have a good working knowlege of PMODE 3, then you pretty much know the workings of the PMODE/W kernel. There are some differences though. The memory system has been completely changed, as has the behavior of the IRQs. You should read this section even if you know PMODE 3. When run under a clean system, XMS, or VCPI, PMODE/W has control of protected mode. In this case, it can set up the system to run as fast as possible under the various conditions. Under DPMI, the DPMI host of the system will have full protected mode control and PMODE/W will install its DOS extensions on top of that. If the system provides both VCPI and DPMI services, PMODE/W will use the VCPI services for faster execution (unless instructed not to by the setup program). When PMODE/W does have protected mode control (under clean/XMS/VCPI), it runs all code at a privilege level of zero. In addition, under a clean or XMS system, paging will not be enabled. This is only a minor speed increase, but there is no real need to manage paging. PMODE/W provides a subset of DPMI 0.9 function calls and general functionality when a DPMI host is not present. PMODE/W will pass any software interrupts from protected to their default real mode handlers (provided no protected mode handlers have been installed for them), just as DPMI will. The general registers will be passed on to the real mode handler, but the segment registers can not be as they have different meanings in real and protected mode. The flags will be passed back from the real mode handler. This provides a simple interface to all real mode interrupt routines which do not take parameters in the segment registers, for example, INT 16h function 00h. Any IRQs that occur in protected mode and have not been hooked by a protected mode handler will be sent on to their real mode handlers. If an IRQ occurs in real mode, and a protected mode handler has hooked that IRQ, it will be sent to the protected mode handler first. The protected mode handler may chain to the real mode handler for that IRQ by calling the previous protected mode handler for that IRQ. This behavior is in accordance with the DPMI standard. If you hook a protected mode IRQ (INT 31h function 0205h), then hook the same IRQ in real mode (INT 31h function 0201h), the protected mode handler will be called if the IRQ occurs in protected mode, and the real mode handler will handle the IRQs if they occur in real mode. Setting up two handlers like this assures minimal latency. This means a handler will get control when the IRQ occurs as soon as physically possible. You should be aware that PMODE/W does not pass INTs 1ch, 23h, or 24h to protected mode from real mode as is specified in DPMI documentation. This means that if you want to hook the BIOS timer tick routine or the DOS break or critical error interrupt, you must set up a real mode handler for them, possibly a real mode callback. Another departure by PMODE/W from official DPMI specifications is in extended memory allocation. DPMI documentation states that the block of extended memory allocated through function 0501h is guaranteed at least paragraph alignment. The PMODE/W DPMI implementation will enforce only DWORD alignment. This is only a brief description of the workings of the PMODE/W kernel. If you want more information on the internals, grab a copy of the PMODE v3 kernel available publicly on the internet and BBSes. Except for the memory system and IRQ hooking, PMODE v3 is very similar to the PMODE/W kernel (being that the PMODE/W kernel is based on it). 1.5 - PMODE/W execution: ------------------------ When a PMODE/W executable is run, PMODE/W will attempt to switch the system into protected mode and load the protected mode portion of the same executable. If there is some error, not enough memory, or a system incompatibility, PMODE/W will exit with an error message. If loading was successful, PMODE/W will pass execution control on to the program. PMODE/W will load any 16bit code and data into low memory, but 32bit code and data may be loaded into low or extended memory depending on avaliability. There are a number of modifiable parameters in the PMODE/W extender executable that affect protected mode execution. For the most part, these parameters deal with memory. PMODE/W allocates one large block of extended memory for its pool from which it provides memory to its client program. There is a maximum value for the extended memory to be allocated. By default, the maximum is all of the extended memory in the system. The maximum value reflects the size of the block you want PMODE/W to take from the system, not necessarily the size of the largest block available to the default C/C++ malloc functions. You may set the maximum to zero to indicate you do not want PMODE/W to allocate ANY extended memory. Another variable specifies the amount of low memory for PMODE/W to TRY to keep free. If PMODE/W can, it will accommodate this value by loading 32bit code and data into extended memory. If there is not enough extended memory available for this, 32bit code and data will be loaded into low memory anyway. If PMODE/W can not keep this much low memory free, it will not exit with an error message. Setting this parameter to a high value will in effect duplicate the DOS/4GW behavior of loading all 32bit code and data into extended memory. If you do not necessarily need any extra low memory free during the execution of your program, you may set this value to zero. There is a group of parameters that specify the number and size of nested mode switch stacks. Whenever you do a call to real mode, or a callback or IRQ is passed from real mode to its hook in protected mode, a nested stack is used. These parameters have meaning only if the program is not run under a DPMI system. If a DPMI host is in place when the program is run, it provides its own nested stacks for mode switches. The number of nested stacks directly affects the number of nested mode switches your program can do using the various mode switch methods. The size of both the real mode and protected mode nested stacks can also be specified. By default, these values are high enough for normal operation. However, if you are intending to use a lot of stack variables in a protected mode IRQ handler, or a lot of recursive calls, you may need to increase the size of the protected mode nested stacks. The more nested stacks you specify and the larger they are, the more low memory is needed by PMODE/W during execution. Another group of variables that has meaning only under clean/XMS/VCPI execution specify the number of selectors and DPMI callbacks you want PMODE/W to make available. The more selectors and callbacks you want, the more low memory is used by PMODE/W, though the amount of low memory used for each is quite low so that large numbers of each can be specified. There will usually be a little less than the number of selectors you request available to your program due to the protected mode system and C/C++ code using some of them. There are three other misc parameters that can be set. There is a maximum number of page tables to use under a VCPI system. Each page table allocated requires 4k of low memory to be used by PMODE/W and maps 4M of memory. This directly affects the maximum amount of extended memory available under a VCPI system. This parameter is only the maximum number of page tables to allow. At run-time, only as many page tables will be allocated as are needed. Under a clean/XMS system, no page tables are required, so this parameter has no meaning. But under VCPI, you may want to restrict the number of page tables to save low memory if you do not need more than a certain amount of extended memory. This puts a maximum ceiling on extended memory under VCPI which may be lower than the maximum actually specified in the other variable. The second parameter specifies the order of DPMI and VCPI detection. By default, VCPI will be checked before DPMI, but you may set DPMI to be checked before VCPI. The third variable specifies how many pages to reserve for physical address mapping calls (INT 31h function 0800h) under VCPI. Each page will allow you to map up to 4M of address space and takes up 4k of extended memory. So for example, if you intend to map a 2M frame buffer of a video card, you will need only one page. You may set this parameter to zero if you do not intend to map any physical addresses. The setup program PMWSETUP will allow you to modify these variables in the PMODE/W extender itself, or specifically, in any program compiled with PMODE/W. The setup program will enforce any necessary minimums and maximums for the values, but there are certain things you should be aware of. You will be allowed to set the number of nested protected mode stacks to zero. But keep in mind this will only work if you do not use any DPMI callbacks and do not hook any IRQs in protected mode. Also, do not specify any less than two real mode nested stacks if you will be calling the old IRQ handler in a protected mode IRQ handler. It is wise to keep the number of nested stacks above 4, but if you follow these strict rules, you may set the number lower to save some low memory. If you set these numbers lower, and get problems, try increasing them and the associated stack sizes. In the setup program itself, the arrow keys move the selection bar, SPACE toggles hex/decimal display, and ENTER modifies the currently selected value. 1.6 - Terms for non-commercial use: ----------------------------------- You are hereby permitted to use this DOS extender in any and all non-commercial and non-shareware software programs free of any financial obligation to us, provided that if the program is distributed, it is distributed to the public, free of any charge for the program itself. There is no restriction on what kind of reselling of the above mentioned program is done (shareware houses, CD-ROMs, etc...), as long as the program is available to the public with no financial obligation to the author(s). The only thing we ask in this case is that you credit us in your production for the DOS extender. It would also be nice, but not necessary, if you dropped us a note informing us of your use of PMODE/W in some production. 1.7 - Licensing PMODE/W for commercial use: ------------------------------------------- If you wish to use PMODE/W in a commercial, shareware, or any program which is to be sold or has attached to it an obligation to buy something, you MUST purchase a commercial distribution license. This license will allow royalty free distribution of one application using PMODE/W. A separate license is required for each application in which PMODE/W is used. A single licensed application may consist of more than one actual program, but all the programs within that application must be available only as part of the whole package and may not be sold separately for their own intrinsic value. The license fee is $500 U.S. for a commercial or shareware program. Once purchased, this license is valid for the life of the program, including any and all major revisions. 1.8 - Contact information: -------------------------- If you are interested in licensing PMODE/W for a commercial or shareware program, you may contact us in the following manner: ) Send mail to: Ryan Cramer 8300 Riding Ridge Place McLean, VA 22102 USA ) Send E-mail to: rcramer1@osf1.gmu.edu ) Drop a note to the sysop on the Data Connection BBS at: +1-703-506-8598 +1-703-847-0861 ) For technical questions, drop a note to: daredevi@dorsai.dorsai.org ------------------------------------------------------------------------------ ------------------- 2 - Supported DPMI INT 31h functions --------------------- ------------------------------------------------------------------------------ PMODE/W duplicates a subset of DPMI protected mode functions. These functions are available ONLY in protected through INT 31h. They provide descriptor services, extended memory services, interrupt services, translation services, and some other misc things. A function is called by setting AX to the function code, setting any other registers for the function, and executing an INT 31h. Upon return, the carry flag will be clear if the function was successful. If the carry flag is set, the function failed. All other registers are preserved unless otherwise specified. In addition to the functions listed here, functions 0600h and 0601h will return with the carry flag clear to stay compatible with code that locks memory since PMODE/W does not support virtual memory. 2.0 - Function 0000h - Allocate Descriptors: -------------------------------------------- Allocates one or more descriptors in the client's descriptor table. The descriptor(s) allocated must be initialized by the application with other function calls. In: AX = 0000h CX = number of descriptors to allocate Out: if successful: carry flag clear AX = base selector if failed: carry flag set Notes: ) If more that one descriptor was requested, the function returns a base selector referencing the first of a contiguous array of descriptors. The selector values for subsequent descriptors in the array can be calculated by adding the value returned by INT 31h function 0003h. ) The allocated descriptor(s) will be set to expand-up writeable data, with the present bit set and a base and limit of zero. The privilege level of the descriptor(s) will match the client's code segment privilege level. 2.1 - Function 0001h - Free Descriptor: --------------------------------------- Frees a descriptor. In: AX = 0001h BX = selector for the descriptor to free Out: if successful: carry flag clear if failed: carry flag set Notes: ) Each descriptor allocated with INT 31h function 0000h must be freed individually with the function. Even if it was previously allocated as part of a contiguous array of descriptors. ) Under DPMI 1.0/VCPI/XMS/raw, any segment registers which contain the selector being freed are zeroed by this function. 2.2 - Function 0003h - Get Selector Increment Value: ---------------------------------------------------- The Allocate Descriptors function (0000h) can allocate an array of contiguous descriptors, but only return a selector for the first descriptor. The value returned by this function can be used to calculate the selectors for subsequent descriptors in the array. In: AX = 0003h Out: always successful: carry flag clear AX = selector increment value Notes: ) The increment value is always a power of two. 2.3 - Function 0006h - Get Segment Base Address: ------------------------------------------------ Returns the 32bit linear base address from the descriptor table for the specified segment. In: AX = 0006h BX = selector Out: if successful: carry flag clear CX:DX = 32bit linear base address of segment if failed: carry flag set Notes: ) Client programs must use the LSL instruction to query the limit for a descriptor. 2.4 - Function 0007h - Set Segment Base Address: ------------------------------------------------ Sets the 32bit linear base address field in the descriptor for the specified segment. In: AX = 0007h BX = selector CX:DX = 32bit linear base address of segment Out: if successful: carry flag clear if failed: carry flag set Notes: ) Under DPMI 1.0/VCPI/XMS/raw, any segment register which contains the selector specified in register BX will be reloaded. DPMI 0.9 may do this, but it is not guaranteed. ) We hope you have enough sense not to try to modify your current CS or SS descriptor. 2.5 - Function 0008h - Set Segment Limit: ----------------------------------------- Sets the limit field in the descriptor for the specified segment. In: AX = 0008h BX = selector CX:DX = 32bit segment limit Out: if successful: carry flag clear if failed: carry flag set Notes: ) The value supplied to the function in CX:DX is the byte length of the segment-1. ) Segment limits greater than or equal to 1M must be page aligned. That is, they must have the low 12 bits set. ) This function has an implicit effect on the "G" bit in the segment's descriptor. ) Client programs must use the LSL instruction to query the limit for a descriptor. ) Under DPMI 1.0/VCPI/XMS/raw, any segment register which contains the selector specified in register BX will be reloaded. DPMI 0.9 may do this, but it is not guaranteed. ) We hope you have enough sense not to try to modify your current CS or SS descriptor. 2.6 - Function 0009h - Set Descriptor Access Rights: ---------------------------------------------------- Modifies the access rights field in the descriptor for the specified segment. In: AX = 0009h BX = selector CX = access rights/type word Out: if successful: carry flag clear if failed: carry flag set Notes: ) The access rights/type word passed to the function in CX has the following format: Bit: 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | G |B/D| 0 | ? | ? | 1 | DPL | 1 |C/D|E/C|W/R| A | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ G - 0=byte granular, 1=page granular B/D - 0=default 16bit, 1=default 32bit DPL - must be equal to caller's CPL C/D - 0=data, 1=code E/C - data: 0=expand-up, 1=expand-down code: must be 0 (non-conforming) W/R - data: 0=read, 1=read/write code: must be 1 (readable) A - 0=not accessed, 1=accessed 0 - must be 0 1 - must be 1 ? - ignored ) Client programs should use the LAR instruction to examine the access rights of a descriptor. ) Under DPMI 1.0/VCPI/XMS/raw, any segment register which contains the selector specified in register BX will be reloaded. DPMI 0.9 may do this, but it is not guaranteed. ) We hope you have enough sense not to try to modify your current CS or SS descriptor. 2.7 - Function 000Ah - Create Alias Descriptor: ----------------------------------------------- Creates a new data descriptor that has the same base and limit as the specified descriptor. In: AX = 000ah BX = selector Out: if successful: carry flag clear AX = data selector (alias) if failed: carry flag set Notes: ) The selector supplied to the function may be either a data descriptor or a code descriptor. The alias descriptor created is always an expand-up writeable data segment. ) The descriptor alias returned by this function will not track changes to the original descriptor. 2.8 - Function 000Bh - Get Descriptor: -------------------------------------- Copies the descriptor table entry for the specified selector into an 8 byte buffer. In: AX = 000bh BX = selector ES:EDI = selector:offset of 8 byte buffer Out: if successful: carry flag clear buffer pointed to by ES:EDI contains descriptor if failed: carry flag set 2.9 - Function 000Ch - Set Descriptor: -------------------------------------- Copies the contents of an 8 byte buffer into the descriptor for the specified selector. In: AX = 000ch BX = selector ES:EDI = selector:offset of 8 byte buffer containing descriptor Out: if successful: carry flag clear if failed: carry flag set ) The descriptors access rights/type word at offset 5 within the descriptor follows the same format and restrictions as the access rights/type parameter CX to the Set Descriptor Access Rights function (0009h). ) Under DPMI 1.0/VCPI/XMS/raw, any segment register which contains the selector specified in register BX will be reloaded. DPMI 0.9 may do this, but it is not guaranteed. ) We hope you have enough sense not to try to modify your current CS or SS descriptor or the descriptor of the buffer. 2.10 - Function 0100h - Allocate DOS Memory Block: -------------------------------------------------- Allocates low memory through DOS function 48h and allocates it a descriptor. In: AX = 0100h BX = paragraphs to allocate Out: if successful: carry flag clear AX = real mode segment address DX = protected mode selector for memory block if failed: carry flag set AX = DOS error code BX = size of largest available block 2.11 - Function 0101h - Free DOS Memory Block: ---------------------------------------------- Frees a low memory block previously allocated by function 0100h. In: AX = 0101h DX = protected mode selector for memory block Out: if successful: carry flag clear if failed: carry flag set AX = DOS error code 2.12 - Function 0102h - Resize DOS Memory Block: ------------------------------------------------ Resizes a low memory block previously allocated by function 0100h In: AX = 0102h BX = new block size in paragraphs DX = protected mode selector for memory block Out: if successful: carry flag clear if failed: carry flag set AX = DOS error code BX = size of largest available block 2.13 - Function 0200h - Get Real Mode Interrupt Vector: ------------------------------------------------------- Returns the real mode segment:offset for the specified interrupt vector. In: AX = 0200h BL = interrupt number Out: always successful: carry flag clear CX:DX = segment:offset of real mode interrupt handler Notes: ) The value returned in CX is a real mode segment address, not a protected mode selector. 2.14 - Function 0201h - Set Real Mode Interrupt Vector: ------------------------------------------------------- Sets the real mode segment:offset for the specified interrupt vector. In: AX = 0201h BL = interrupt number CX:DX = segment:offset of real mode interrupt handler Out: always successful: carry flag clear Notes: ) The value passed in CX must be a real mode segment address, not a protected mode selector. Consequently, the interrupt handler must either reside in DOS memory (below the 1M boundary) or the client must allocate a real mode callback address. 2.15 - Function 0204h - Get Protected Mode Interrupt Vector: ------------------------------------------------------------ Returns the address of the current protected mode interrupt handler for the specified interrupt. In: AX = 0204h BL = interrupt number Out: always successful: carry flag clear CX:EDX = selector:offset of protected mode interrupt handler Notes: ) The value returned in CX is a valid protected mode selector, not a real mode segment address. 2.16 - Function 0205h - Set Protected Mode Interrupt Vector: ------------------------------------------------------------ Sets the address of the protected mode interrupt handler for the specified interrupt. In: AX = 0205h BL = interrupt number CX:EDX = selector offset of protected mode interrupt handler Out: if successful: carry flag clear if failed: carry flag set Notes: ) The value passed in CX must be a valid protected mode selector, not a real mode segment address. 2.17 - Function 0300h - Simulate Real Mode Interrupt: ----------------------------------------------------- Simulates an interrupt in real mode. The function transfers control to the address specified by the real mode interrupt vector. The real mode handler must return by executing an IRET. In: AX = 0300h BL = interrupt number BH = must be 0 CX = number of words to copy from the protected mode stack to the real mode stack ES:EDI = selector:offset of real mode register data structure in the following format: Offset Length Contents 00h 4 EDI 04h 4 ESI 08h 4 EBP 0ch 4 reserved, ignored 10h 4 EBX 14h 4 EDX 18h 4 ECX 1ch 4 EAX 20h 2 CPU status flags 22h 2 ES 24h 2 DS 26h 2 FS 28h 2 GS 2ah 2 IP (reserved, ignored) 2ch 2 CS (reserved, ignored) 2eh 2 SP 30h 2 SS Out: if successful: carry flag clear ES:EDI = selector offset of modified real mode register data structure if failed: carry flag set Notes: ) The CS:IP in the real mode register data structure is ignored by this function. The appropriate interrupt handler will be called based on the value passed in BL. ) If the SS:SP fields in the real mode register data structure are zero, a real mode stack will be provided by the host. Otherwise the real mode SS:SP will be set to the specified values before the interrupt handler is called. ) The flags specified in the real mode register data structure will be put on the real mode interrupt handler's IRET frame. The interrupt handler will be called with the interrupt and trace flags clear. ) Values placed in the segment register positions of the data structure must be valid for real mode. That is, the values must be paragraph addresses, not protected mode selectors. ) The target real mode handler must return with the stack in the same state as when it was called. This means that the real mode code may switch stacks while it is running, but must return on the same stack that it was called on and must return with an IRET. ) When this function returns, the real mode register data structure will contain the values that were returned by the real mode interrupt handler. The CS:IP and SS:SP values will be unmodified in the data structure. ) It is the caller's responsibility to remove any parameters that were pushed on the protected mode stack. 2.18 - Function 0301h - Call Real Mode Procedure With Far Return Frame: ----------------------------------------------------------------------- Simulates a FAR CALL to a real mode procedure. The called procedure must return by executing a RETF instruction. In: AX = 0301h BH = must be 0 CX = number of words to copy from the protected mode stack to the real mode stack ES:EDI = selector:offset of real mode register data structure in the following format: Offset Length Contents 00h 4 EDI 04h 4 ESI 08h 4 EBP 0ch 4 reserved, ignored 10h 4 EBX 14h 4 EDX 18h 4 ECX 1ch 4 EAX 20h 2 CPU status flags 22h 2 ES 24h 2 DS 26h 2 FS 28h 2 GS 2ah 2 IP 2ch 2 CS 2eh 2 SP 30h 2 SS Out: if successful: carry flag clear ES:EDI = selector offset of modified real mode register data structure if failed: carry flag set Notes: ) The CS:IP in the real mode register data structure specifies the address of the real mode procedure to call. ) If the SS:SP fields in the real mode register data structure are zero, a real mode stack will be provided by the host. Otherwise the real mode SS:SP will be set to the specified values before the procedure is called. ) Values placed in the segment register positions of the data structure must be valid for real mode. That is, the values must be paragraph addresses, not protected mode selectors. ) The target real mode procedure must return with the stack in the same state as when it was called. This means that the real mode code may switch stacks while it is running, but must return on the same stack that it was called on and must return with a RETF and should not clear the stack of any parameters that were passed to it on the stack. ) When this function returns, the real mode register data structure will contain the values that were returned by the real mode procedure. The CS:IP and SS:SP values will be unmodified in the data structure. ) It is the caller's responsibility to remove any parameters that were pushed on the protected mode stack. 2.19 - Function 0302h - Call Real Mode Procedure With IRET Frame: ----------------------------------------------------------------- Simulates a FAR CALL with flags pushed on the stack to a real mode routine. The real mode procedure must return by executing an IRET instruction or a RETF 2. In: AX = 0301h BH = must be 0 CX = number of words to copy from the protected mode stack to the real mode stack ES:EDI = selector:offset of real mode register data structure in the following format: Offset Length Contents 00h 4 EDI 04h 4 ESI 08h 4 EBP 0ch 4 reserved, ignored 10h 4 EBX 14h 4 EDX 18h 4 ECX 1ch 4 EAX 20h 2 CPU status flags 22h 2 ES 24h 2 DS 26h 2 FS 28h 2 GS 2ah 2 IP 2ch 2 CS 2eh 2 SP 30h 2 SS Out: if successful: carry flag clear ES:EDI = selector offset of modified real mode register data structure if failed: carry flag set Notes: ) The CS:IP in the real mode register data structure specifies the address of the real mode procedure to call. ) If the SS:SP fields in the real mode register data structure are zero, a real mode stack will be provided by the host. Otherwise the real mode SS:SP will be set to the specified values before the procedure is called. ) The flags specified in the real mode register data structure will be put on the real mode procedure's IRET frame. The procedure will be called with the interrupt and trace flags clear. ) Values placed in the segment register positions of the data structure must be valid for real mode. That is, the values must be paragraph addresses, not protected mode selectors. ) The target real mode procedure must return with the stack in the same state as when it was called. This means that the real mode code may switch stacks while it is running, but must return on the same stack that it was called on and must return with an IRET or discard the flags from the stack with a RETF 2 and should not clear the stack of any parameters that were passed to it on the stack. ) When this function returns, the real mode register data structure will contain the values that were returned by the real mode procedure. The CS:IP and SS:SP values will be unmodified in the data structure. ) It is the caller's responsibility to remove any parameters that were pushed on the protected mode stack. 2.20 - Function 0303h - Allocate Real Mode Callback Address: ------------------------------------------------------------ Returns a unique real mode segment:offset, known as a "real mode callback", that will transfer control from real mode to a protected mode procedure. Callback addresses obtained with this function can be passed by a protected mode program to a real mode application, interrupt handler, device driver, TSR, etc... so that the real mode program can call procedures within the protected mode program. In: AX = 0303h DS:ESI = selector:offset of protected mode procedure to call ES:EDI = selector:offset of 32h byte buffer for real mode register data structure to be used when calling the callback routine. Out: if successful: carry flag clear CX:DX = segment:offset of real mode callback if failed: carry flag set Notes: ) A descriptor may be allocated for each callback to hold the real mode SS descriptor. Real mode callbacks are a limited system resource. A client should release a callback that it is no longer using. 2.21 - Function 0304h - Free Real Mode Callback Address: -------------------------------------------------------- Releases a real mode callback address that was previously allocated with the Allocate Real Mode Callback Address function (0303h). In: AX = 0304h CX:DX = segment:offset of real mode callback to be freed Out: if successful: carry flag clear if failed: carry flag set Notes: ) Real mode callbacks are a limited system resource. A client should release any callback that it is no longer using. 2.22 - Function 0305h - Get State Save/Restore Addresses: --------------------------------------------------------- Returns the address of two procedures used to save and restore the state of the current task's registers in the mode (protected or real) which is not currently executing. In: AX = 0305h Out: always successful: carry flag clear AX = size of buffer in bytes required to save state BX:CX = segment:offset of real mode routine used to save/restore state SI:EDI = selector:offset of protected mode routine used to save/restore state Notes: ) The real mode segment:offset returned by this function should be called only in real mode to save/restore the state of the protected mode registers. The protected mode selector:offset returned by this function should be called only in protected mode to save/restore the state of the real mode registers. ) Both of the state save/restore procedures are entered by a FAR CALL with the following parameters: AL = 0 to save state = 1 to restore state ES:(E)DI = (selector or segment):offset of state buffer The state buffer must be at least as large as the value returned in AX by INT 31h function 0305h. The state save/restore procedures do not modify any registers. DI must be used for the buffer offset in real mode, EDI must be used in protected mode. ) Some DPMI hosts and VCPI/XMS/raw will not require the state to be saved, indicating this by returning a buffer size of zero in AX. In such cases, that addresses returned by this function can still be called, although they will simply return without performing any useful function. ) Clients do not need to call the state save/restore procedures before using INT 31h function 0300h, 0301h, or 0302h. The state save/restore procedures are provided for clients that use the raw mode switch services only. 2.23 - Function 0306h - Get Raw Mode Switch Addresses: ------------------------------------------------------ Returns addresses that can be called for low level mode switching. In: AX = 0306h Out: always successful: carry flag clear BX:CX = segment:offset of real to protected mode switch procedure SI:EDI = selector:offset of protected to real mode switch procedure Notes: ) The real mode segment:offset returned by this function should be called only in real mode to switch to protected mode. The protected mode selector:offset returned by this function should be called only in protected mode to switch to real mode. ) The mode switch procedures are entered by a FAR JMP to the appropriate address with the following parameters: AX = new DS CX = new ES DX = new SS (E)BX = new (E)SP SI = new CS (E)DI = new (E)IP The processor is placed into the desired mode, and the DS, ES, SS, (E)SP, CS, and (E)IP registers are updated with the specific values. In other words, execution of the client continues in the requested mode at the address provided in registers SI:(E)DI. The values specified to be placed into the segment registers must be appropriate for the destination mode. That is, segment addresses for real mode, and selectors for protected mode. The values in EAX, EBX, ECX, EDX, ESI, and EDI after the mode switch are undefined. EBP will be preserved across the mode switch call so it can be used as a pointer. FS and GS will contain zero after the mode switch. If interrupts are disabled when the mode switch procedure is invoked, they will not be re-enabled by the host (even temporarily). ) It is up to the client to save and restore the state of the task when using this function to switch modes. This requires the state save/restore procedures whose addresses can be obtained with INT 31h function 0305h. 2.24 - Function 0400h - Get Version: ------------------------------------ Returns the version of the DPMI Specification implemented by the DPMI host. The client can use this information to determine what functions are available. In: AX = 0400h Out: always successful: carry flag clear AH = DPMI major version as a binary number (VCPI/XMS/raw returns 1) AL = DPMI minor version as a binary number (VCPI/XMS/raw returns 0) BX = flags: Bits Significance 0 0 = host is 16bit (PMODE/W never runs under one of these) 1 = host is 32bit 1 0 = CPU returned to V86 mode for reflected interrupts 1 = CPU returned to real mode for reflected interrupts 2 0 = virtual memory not supported 1 = virtual memory supported 3-15 reserved CL = processor type: 03h = 80386 04h = 80486 05h = 80586 06h-ffh = reserved DH = current value of master PIC base interrupt (low 8 IRQs) DL = current value of slave PIC base interrupt (high 8 IRQs) Notes: ) The major and minor version numbers are binary, not BCD. So a DPMI 0.9 implementation would return AH as 0 and AL as 5ah (90). 2.25 - Function 0500h - Get Free Memory Information: ---------------------------------------------------- Returns information about the amount of available memory. Since DPMI clients could be running in a multitasking environment, the information returned by this function should be considered advisory. In: AX = 0500h ES:EDI = selector:offset of 48 byte buffer Out: if successful: carry flag clear buffer is filled with the following information: Offset Length Contents 00h 4 Largest available free block in bytes 04h 2ch Other fields only supplied by DPMI if failed: carry flag set Notes: ) Only the first field of the structure is guaranteed to contain a valid value. Any fields that are not supported by the host will be set to -1 (0ffffffffh) to indicate that the information is not available. 2.26 - Function 0501h - Allocate Memory Block: ---------------------------------------------- Allocates a block of extended memory. In: AX = 0501h BX:CX = size of block in bytes (must be non-zero) Out: if successful: carry flag clear BX:CX = linear address of allocated memory block SI:DI = memory block handle (used to resize and free block) if failed: carry flag set Notes: ) The allocated block is guaranteed to have at least dword alignment. ) This function does not allocate any descriptors for the memory block. It is the responsibility of the client to allocate and initialize any descriptors needed to access the memory with additional function calls. 2.27 - Function 0502h - Free Memory Block: ------------------------------------------ Frees a memory block previously allocated with the Allocate Memory Block function (0501h). In: AX = 0502h SI:DI = memory block handle Out: if successful: carry flag clear if failed: carry flag set Notes: ) No descriptors are freed by this call. It is the client's responsibility to free any descriptors that it previously allocated to map the memory block. Descriptors should be freed before memory blocks. 2.28 - Function 0503h - Resize Memory Block: -------------------------------------------- Changes the size of a memory block previously allocated with the Allocate Memory Block function (0501h). In: AX = 0503h BX:CX = new size of block in bytes (must be non-zero) SI:DI = memory block handle Out: if successful: carry flag clear BX:CX = new linear address of memory block SI:DI = new memory block handle if failed: carry flag set Notes: ) After this function returns successfully, the previous handle for the memory block is invalid and should not be used anymore. ) It is the client's responsibility to update any descriptors that map the memory block with the new linear address after resizing the block. 2.29 - Function 0800h - Physical Address Mapping: ------------------------------------------------- Converts a physical address into a linear address. This functions allows the client to access devices mapped at a specific physical memory address. Examples of this are the frame buffers of certain video cards in extended memory. In: AX = 0800h BX:CX = physical address of memory SI:DI = size of region to map in bytes Out: if successful: carry flag clear BX:CX = linear address that can be used to access the physical memory if failed: carry flag set Notes: ) It is the caller's responsibility to allocate and initialize a descriptor for access to the memory. ) Clients should not use this function to access memory below the 1 MB boundary. 2.30 - Function 0801h - Free Physical Address Mapping: ------------------------------------------------------ Releases a mapping of physical to linear addresses that was previously obtained with function 0800h. In: AX = 0801h BX:CX = linear address returned by physical address mapping call Out: if successful: carry flag clear if failed: carry flag set Notes: ) The client should call this function when it is finished using a device previously mapped to linear addresses with function 0801h. 2.31 - Function 0900h - Get and Disable Virtual Interrupt State: ---------------------------------------------------------------- Disables the virtual interrupt flag and returns the previous state of it. In: AX = 0900h Out: always successful: carry flag clear AL = 0 if virtual interrupts were previously disabled AL = 1 if virtual interrupts were previously enabled Notes: ) AH is not changed by this function. Therefore the previous state can be restored by simply executing another INT 31h. ) A client that does not need to know the prior interrupt state can execute the CLI instruction rather than calling this function. The instruction may be trapped by a DPMI host and should be assumed to be very slow. 2.32 - Function 0901h - Get and Enable Virtual Interrupt State: --------------------------------------------------------------- Enables the virtual interrupt flag and returns the previous state of it. In: AX = 0901h Out: always successful: carry flag clear AL = 0 if virtual interrupts were previously disabled AL = 1 if virtual interrupts were previously enabled Notes: ) AH is not changed by this function. Therefore the previous state can be retstored by simply executing another INT 31h. ) A client that does not need to know the prior interrupt state can execute the STI instruction rather than calling this function. The instruction may be trapped by a DPMI host and should be assumed to be very slow. 2.33 - Function 0902h - Get Virtual Interrupt State: ---------------------------------------------------- Returns the current state of the virtual interrupt flag. In: AX = 0902h Out: always successful: carry flag clear AL = 0 if virtual interrupts are disabled AL = 1 if virtual interrupts are enabled Notes: ) This function should be used in preference to the PUSHF instruction to examine the interrupt flag, because the PUSHF instruction returns the physical interrupt flag rather than the virtualized interrupt flag. On some DPMI hosts, the physical interrupt flag will always be enabled, even when the hardware interrupts are not being passed through to the client. ------------------------------------------------------------------------------ -------------- 3 - Supported DOS extended INT 21h functions ------------------ ------------------------------------------------------------------------------ For the most part, PMODE/W extends only the most widely used DOS functions. The term "extend" means to extend real mode 16:16 pointers which have a limit of 1MB into the full protected mode range of 16:32 pointers with a range of 4GB. Since DOS can only address memory under 1MB, we must buffer any data that is to be passed to or from DOS in low memory. Only DOS functions which use 16:16 pointers or segment registers need to be extended. This means that DOS functions that are not listed here can still be used provided they don't make use of those kinds of parameters. Examples of such functions are INT 21h AH=30h or INT 21h AH=2, etc. The following is a detailed list of all functions extended by PMODE/W. All segment registers used as parameters must be valid protected mode selectors. Any functions that are not listed here will be passed on to the real mode INT 21h handler without any buffering or modification. This and the other sections on interrupts are provided as reference as to how PMODE/W deals with these interrupts. It is assumed the reader is familiar with the normal real mode operation of these functions. 3.0 - Function 09h - Write String to Standard Output: ----------------------------------------------------- In: AH = 09h DS:EDX -> '$' terminated string to write Out: always successful 3.1 - Function 1Ah - Set Disk Transfer Area: -------------------------------------------- In: AH = 1Ah DS:EDX -> buffer for DTA Out: always successful Notes: ) PMODE/W keeps an internal DTA buffer in low memory that is used to buffer any functions which use the DTA. After calling the real mode DOS function, the data will be transfered into the buffer specified by DS:EDX. 3.2 - Function 1Bh - Get Allocation Information for Default Drive: ------------------------------------------------------------------ In: AH = 1Bh Out: always successful: AL = sectors per cluster ECX = bytes per sector EDX = total number of clusters DS:EBX -> media ID byte Notes: ) This functions simply converts the real mode segment:offset returned by DOS to a protected mode selector:offset. 3.3 - Function 1Ch - Get Allocation Information for Specific Drive: ------------------------------------------------------------------- In: AH = 1Ch DL = drive number Out: if successful: AL = sectors per cluster ECX = bytes per sector EDX = total number of clusters DS:EBX -> media ID byte if failed: AL = FFh (invalid drive) Notes: ) This functions simply converts the real mode segment:offset returned by DOS to a protected mode selector:offset. 3.4 - Function 1Fh - Get Drive Parameter Block for Default Drive: ----------------------------------------------------------------- In: AH = 1Fh Out: if successful: AL = 0 DS:EBX -> drive parameter block if failed: AL = FFh (invalid drive) Notes: ) This functions simply converts the real mode segment:offset returned by DOS to a protected mode selector:offset. 3.5 - Function 25h - Set Interrupt Vector: ------------------------------------------ In: AH = 25h AL = interrupt number DS:EDX -> interrupt routine Out: if successful: carry flag clear if failed: carry flag set Notes: ) This function is equivalent to INT 31h function 0205h. 3.6 - Function 2Fh - Get Disk Transfer Area: -------------------------------------------- In: AH = 2Fh Out: always successful: ES:EBX -> DTA Notes: ) This function will return the value that was previously set by function 1Ah or the default buffer if function 1Ah was not called. 3.7 - Function 32h - Get Drive Parameter Block for Specific Drive: ------------------------------------------------------------------ In: AH = 32h DL = drive number Out: if successful: AL = 0 DS:EBX -> drive parameter block if failed: AL = FFh (invalid drive) Notes: ) This functions simply converts the real mode segment:offset returned by DOS to a protected mode selector:offset. 3.8 - Function 34h - Get Address of InDOS Flag: ----------------------------------------------- In: AH = 34h Out: always successful: ES:EBX -> InDOS flag Notes: ) This functions simply converts the real mode segment:offset returned by DOS to a protected mode selector:offset. 3.9 - Function 35h - Get Interrupt Vector: ------------------------------------------ In: AH = 35h AL = interrupt number Out: always successful: ES:EBX -> interrupt routine Notes: ) This function is equivalent to INT 31h function 0204h. 3.10 - Function 39h - Create Subdirectory: ------------------------------------------ In: AH = 39h DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear if failed: carry flag set EAX = error code 3.11 - Function 3Ah - Remove Subdirectory: ------------------------------------------ In: AH = 3Ah DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear if failed: carry flag set EAX = error code 3.12 - Function 3Bh - Set Directory: ------------------------------------ In: AH = 3Bh DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear if failed: carry flag set EAX = error code 3.13 - Function 3Ch - Create File: ---------------------------------- In: AH = 3Ch CX = attribute DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear EAX = handle if failed: carry flag set EAX = error code 3.14 - Function 3Dh - Open File: -------------------------------- In: AH = 3Dh AL = open code DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear EAX = handle if failed: carry flag set EAX = error code 3.15 - Function 3Fh - Read From File: ------------------------------------- In: AH = 3Fh BX = file handle ECX = number of bytes to read DS:EDX -> buffer to read to Out: if successful: carry flag clear EAX = number of bytes read if failed: carry flag set EAX = error code 3.16 - Function 40h - Write To File: ------------------------------------ In: AH = 40h BX = file handle ECX = number of bytes to write DS:EDX -> buffer to write from Out: if successful: carry flag clear EAX = number of bytes written if failed: carry flag set EAX = error code 3.17 - Function 41h - Delete File: ---------------------------------- In: AH = 41h DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear if failed: carry flag set EAX = error code 3.18 - Function 43h - Get/Set File Attributes: ---------------------------------------------- In: AH = 43h AL = function code CX = desired attributes DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear CX = current attributes if failed: carry flag set EAX = error code 3.19 - Function 47h - Get Directory Path: ----------------------------------------- In: AH = 47h DL = drive number DS:ESI -> buffer for path Out: if successful: carry flag clear buffer pointer to by DS:ESI is filled with the path if failed: carry flag set EAX = error code 3.20 - Function 48h - Allocate Memory Block: -------------------------------------------- In: AH = 48h BX = paragraphs to allocate Out: if successful: carry flag clear EAX = selector for memory block if failed: carry flag set EAX = error code EBX = maximum paragraphs available Notes: ) This function allocates ONLY DOS memory below 1MB. ) This function is equivalent to INT 31h function 0100h. 3.21 - Function 49h - Free Memory Block: ---------------------------------------- In: AH = 49h ES = selector for memory block Out: if successful: carry flag clear ES = NULL selector (zeroed to prevent loading an invalid selector) if failed: carry flag set EAX = error code Notes: ) This function is equivalent to INT 31h function 0101h. 3.22 - Function 4Ah - Resize Memory Block: ------------------------------------------ In: AH = 4Ah BX = total paragraphs to allocate ES = selector Out: if successful: carry flag clear if failed: carry flag set EAX = error code EBX = maximum paragraphs available for specified memory block Notes: ) This function is equivalent to INT 31h function 0102h. 3.23 - Function 4Bh - Sub-Function 00h - Load and Execute Program: ------------------------------------------------------------------ In: AH = 4Bh AL = 00h DS:EDX -> path name ES:EBX -> parameter block Out: if successful: carry flag clear if failed: carry flag set Notes: ) In order to overcome DOS's inability to access data over 1 MB, the environment specified in the parameter block will be copied into an intermediate buffer before being passed on to DOS. The buffer will be allocated through DOS function 48h and freed through 49h when the program is done executing. There must be enough available low memory to hold the environment data or an error will occur. Keep this in mind when passing an environment using spawnle() and related functions. 3.24 - Function 4Eh - Search for First Filename Match: ------------------------------------------------------ In: AH = 4Eh CX = file attribute DS:EDX -> ASCIIZ path name Out: if successful: carry flag clear if failed: carry flag set EAX = error code Notes: ) PMODE/W keeps an internal DTA buffer in low memory that is used to buffer any functions which use the DTA. After calling the real mode DOS function, the data will be transfered into the buffer specified by function 1Ah or the default buffer if function 1Ah was not called. 3.25 - Function 4Fh - Search for Next Filename Match: ----------------------------------------------------- In: AH = 4Fh Out: if successful: carry flag clear if failed: carry flag set EAX = error code Notes: ) PMODE/W keeps an internal DTA buffer in low memory that is used to buffer any functions which use the DTA. After calling the real mode DOS function, the data will be transfered into the buffer specified by function 1Ah or the default buffer if function 1Ah was not called. 3.26 - Function 56h - Rename File: ---------------------------------- In: AH = 56h DS:EDX -> old filename ES:EDI -> new filename Out: if successful: carry flag clear if failed: carry flag set EAX = error code ------------------------------------------------------------------------------ --------------- 4 - Supported mouse extended INT 33h functions --------------- ------------------------------------------------------------------------------ The mouse functions are technically not part of Watcom C/C++ support because they are not used by any of the libraries. But we extend the most popular functions because they are so widely used. The functions that need to be extended are those that require addresses to be passed in segment registers. All other mouse functions not listed here will work if they do not take segment registers as parameters. This means that in addition to the functions listed here, functions like 0000h, 0001h, 0002h, etc... will work. But functions like 0012h and 0018h will not work directly from protected mode because they pass or return segment registers as parameters or require low memory buffering. You may still use those functions, but you must call them through DPMI and make sure that any code or data they use resides in low memory and the code is real mode code (like DPMI callback if you wish to pass control on to protected mode code from there). 4.0 - Function 0009h - Define Graphics Cursor: ---------------------------------------------- In: AX = 0009h BX = column of cursor hot spot in bitmap CX = row of cursor hot spot in bitmap ES:EDX -> mask bitmap Out: always successful 4.1 - Function 000Ch - Define Interrupt Subroutine Parameters: -------------------------------------------------------------- In: AX = 000Ch CX = call mask ES:EDX -> FAR routine Out: always successful Notes: ) This function will use a DPMI real mode callback to pass control from real mode to your protected mode interrupt subroutine. ) Calling this function with a FAR routine of 0000:00000000 is analogous to calling the real mode mouse driver with an address of 0000:0000 which will undefine the interrupt subroutine. 4.2 - Function 0016h - Save Driver State: ----------------------------------------- In: AX = 0016h BX = size of buffer ES:EDX -> buffer for driver state Out: always successful 4.3 - Function 0017h - Restore Driver State: -------------------------------------------- In: AX = 0017h BX = size of buffer ES:EDX -> buffer containing saved state Out: always successful ------------------------------------------------------------------------------ ------------------------ End of PMODE/W Documentation ------------------------ ------------------------------------------------------------------------------