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Text File | 1990-09-10 | 13.4 KB | 341 lines

EXE2COM 1.05 By Chris Dunford/Cove Software | indicates information changed/added in recent versions. Purpose ------- EXE2COM is a one-for-one replacement for the EXE2BIN program that was formerly distributed with DOS. Beginning with DOS 3.3, EXE2BIN has been moved to the disk that comes with the DOS Technical Reference and thus is not available without extra cost. Usage ----- Usage is identical to DOS's EXE2BIN except that the output file extension defaults to COM rather than BIN, and there are two optional switches. Complete usage is: | EXE2COM [/IR] [d:][path]file[ext] [d:][path][file][ext] The drive and path of the first file default to the current drive and path, if not specified. The extension of the first file defaults to EXE, if not specified. If the second file is completely unspecified, it defaults to the same drive, path, and filename as the first, except that the extension will be COM. If the second file is specified but without an extension, COM will be assumed (this is different from EXE2BIN). If /I is specified, information about the EXE file is displayed and no conversion is performed. The output file name, if specified, is ignored. | If /R is specified and the EXE file contains relocatable items, | the relocation table is displayed (see below). The simplest (and usual) usage is simply: EXE2COM file which will take the named EXE file in the current directory and convert it to a COM file in the same directory. Operation --------- EXE2COM runs the same way as EXE2BIN, with the following exceptions: 1. The binary fixup option of EXE2BIN (IP=0, segment fixups required) is not supported. 2. The EXE file checksum is not verified. 3. Error messages are more useful, and a warning is provided if a COM file is created with an initial IP other than 100H. 4. The default output file extension is COM rather than BIN. Information display ------------------- If you use the /I switch, EXE2COM just displays information about the EXE file and does not attempt to convert it to COM (therefore, the EXE file need not be a convertible file). Here is a typical display, resulting from running EXE2COM on itself (version 1.04) with the /I switch: exe2com.exe (hex) (dec) EXE file size 396B 14699 EXE header size (para) 20 32 Program image size (bytes) 376B 14187 Minimum load size (bytes) 8CDB 36059 Min allocation (para) 557 1367 Max allocation (para) FFFF 65535 * Initial CS:IP 0000:072C * Initial SS:SP 084D:0800 2048 (stack size) * Relocation count 4 4 Relo table start 001E 30 EXE file checksum 411D 16669 Overlay number 0 0 * = this item prevents conversion to BIN/COM The fields that may need some explanation: Program image size: this is the size of the program itself (i.e., the size of the EXE file less the size of the header information). This much memory is required to load a copy of the program's code and pre-allocated data. Minimum load size: at least this much free memory is required in order to run the program. Min/max allocation: the minimum/maximum number of 16-byte paragraphs that will be needed above the end of the program image when it is loaded. Minimum load size is the sum of the program image size and the minimum allocation. Relocation count: see below. If an item is starred (*), this prevents the EXE file from being converted to a COM file. | Relocatable items | ----------------- | The most common reason why a file cannot be converted to COM | or SYS format is that it has "relocatable items." | | A relocatable item is a piece of code that must be "fixed up" | when the program is run because it changes with the program's | load address. Consider this code fragment: | | code segment byte public | mov ax,code | ... | | What gets moved into AX is CODE's segment address, which is | not known until runtime. The assembler can't specify the | value to be loaded into AX because it doesn't know where in | memory the program will be loaded. Only the EXE file loader | can perform this operation; hence, it can't be converted into | a COM or SYS file. | | The EXE file header contains one entry for each such relocatable | item. This entry consists of the segment and offset of the word | that must be fixed up at runtime. Note that the "segment" is | relative to the first segment of the program; the first segment | will be 0000. | | If you see the message "EXE contains relocatable items", you can | ask EXE2COM to find the items by re-running it with the /R | /R switch: | | exe2com /r myprog | | EXE2COM might display something like this: | | relocation table: | 0000:00AF 0000:01C3 | | This shows that there are two relocatable items in the EXE file | and that they are located at the specified segment:offset | addresses. The first relocatable item in this case is located | at offset 00AFh of the program's first segment. | | A list (.LST) file can be very helpful in finding your | relocatable items: for each one (in the opcode column), you will | see a "----" where a number should be. In the example, it | might look like: | | 00AE B8 ---- R mov ax,code | | EXE2COM's relocation table display can be helpful in letting | you know where to look for the error. | | To correct the problem, restate the instruction in a way that | doesn't require a direct reference to a segment. For example, | you might recode "mov ax,code" as "mov ax,cs" (assuming that CS | points to the CODE segment). Error Messages -------------- These are EXE2COM's error messages. If one of these is seen, the EXE file will not be converted and the errorlevel returned by EXE2COM will be 1. ERROR READING EXE HEADER EXE2COM was unable to read the EXE file header from disk. ERROR WRITING OUTPUT FILE EXE2COM was unable to write the converted file to disk. INVALID EXE FILE SIGNATURE The first two bytes of an EXE file should be ASCII 'M' and 'Z'. This was not the case, and it's probably not an EXE file. EXE HAS RELOCATABLE ITEMS In order to be converted to a COM file, an EXE file cannot have any direct references to segments. For example, the assembler instruction "mov ax,code" (where CODE is a segment name) is a segment reference. One or more segment references were found in the EXE file. See above. EXE HAS STACK SEGMENT In order to be converted to a COM file, an EXE file cannot have a stack segment. EXE HAS NONZERO CS In order to be converted to a COM file, an EXE file must have a code segment that begins at offset 0 of the code image in the EXE file. IP NOT 0 OR 100H In order to be converted to a binary file, an EXE file must have an entry point of 0 or 100H within the code segment. For COM files, the entry point should be 100H. For SYS files (device drivers), the entry point should be 0. PROGRAM EXCEEDS 64K In order to be converted to a binary file, the total size of the code to be loaded (including the PSP) must not exceed 64K bytes. UNKNOWN ERROR Internal error. Notify the author. Warning message --------------- EXE2COM has one warning message: COM FILE, INITIAL IP NOT 100H The entry point of all COM files should be 100H. If you are creating a COM file an the entry point is not 100H, EXE2COM will do the job but let you know that there is a potential problem. Source ------ Source code should be included with this archive. Users are encouraged to modify, improve, and/or correct the source for EXE2COM and submit the new program to the author for distribution. Please identify clearly any changes made and stick with portable code to the extent possible (no inline assembler, PLEASE). EXE2COM.EXE was compiled with Microsoft C 6.0, but I believe that it will compile correctly with Borland's Turbo C (I don't have TC, so can't swear to this). It should be easily portable to most other compilers. Public domain ------------- EXE2COM is hereby donated by the author to the public domain. History ------- Version 1.00 04/17/87: Original version by Christopher J. Dunford The Cove Software Group PO Box 1072 Columbia, MD 21044 (301) 992-9371 CompuServe 76703,2002 Version 1.01: port to Turbo C by Roger Schlafly Borland International Scotts Valley, CA 95066 CompuServe 76067,511 Version 1.02 11/22/87: bug fix for even 512-byte file made to Turbo C port by Chris Blum ( Consultant ) 509 West Main, Front Ashland, Ohio 44805 CompuServe 76625,1041 Chris Dunford duplicated the fix in the C86 source. Version 1.03 12/30/87: by Chris Dunford Ported to Microsoft C 5.0. This is now the "official" version. Increased size of I/O buffer to 4K for speed reasons. EXE2COM 1.03 is twice as fast as 1.02 and slightly faster than EXE2BIN. Version 1.04 03/08/88: by Chris Dunford Cleaned up some old code from the original quickie. Source should now compile under either MSC or TC. Added /I switch. In earlier versions, we defined an error code for nonzero CS, but didn't actually check; now we do. Version 1.05 08/23/90: by Chris Dunford Added /R (relo table) switch ----------------end-of-author's-documentation--------------- Software Library Information: This disk copy provided as a service of Public (software) Library We are not the authors of this program, nor are we associated with the author in any way other than as a distributor of the program in accordance with the author's terms of distribution. Please direct shareware payments and specific questions about this program to the author of the program, whose name appears elsewhere in this documentation. 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