[cctalk] Re: Running DOS executables on other versions of DOSRe: Looking for Sharp PC-5000 disk drive (CE-510F or possibly MZ-80B)

On Thu, 17 Oct 2024, Steve Lewis via cctalk wrote: Try te VER command, to confirm whether what is running is 2.00 Back in 1982?, when PC-DOS 1.10/1.25 came out, with different disk format, there were problems. If you stuck one of those disks into a machine running PC-DOS 1.00, and ran CHKDSK, it would proceed to gladly "repair" problems with the disk rendering it unusable. (well, alot of tedious manual repair of the DIRectory needed) SO, MICROS~1 eventually changed CHKDSK, to not make repairs unless you had used the /F (fix) option, and explicitly asking you whether you wanted it to do the "repairs" (I had an interesting conversation with Jef Raskin about his view that "if a disk is unreadable, and therefore presumably blank, The computer should just go ahead anf FORMAT it") Then, they made another change. EVERY executable program included with DOS, before it runs would check the currently running DOS version, and refuse to run if it was the wrong DOS version running. NOT ALL programs had a problem with running under another version, but they had to be cautious.. That created problems with some executables, such as LINK and EXE2BIN that were acquired with one version of DOS, but were needed on other versions. The solution to THAT in DOS 5.00? was SETVER. Setver lets DOS lie about it's age! So, when you want to use DOS 2.00 LINK, you can use setver to tell DOS, "If LINK asks the DOS version, tell it 2.00", etc. Obviously you don't have SETVER, that came along later to solve that problem. SO, you need to do a mnor patch. You could seek out a copy of DOS 2.00 FORMAT. OR, since the differences do NOT matter, you can patch FORMAT to not care about which DOS version is running. It will be simplest if you use a relatively old verstion of FORMAT that is a .COM file, not a .EXE Unfortunately the filename won't work for determining that. (later versions of DOS, when progams became too bulky for tiny memory model, they used .EXE programs, but renamed them .COM! Fortunately, DOS 2.11 should be ideal. The sure way to tell whether itis REALLY .COM or .EXE is whether the first two bytes of te file are "MZ" (Mark Zbikowski!) ALL .EXE files have his initials as the first two bytes of the file, disunirregardless of whether the filename claims to be .COM or .EXE REAL .COM programs will NOT start with "MZ" Load it into DEBUG DEBUG FORMAT.COM (any version of DEBUG that works for you, on any computer) Use the U command ("UNassemble") find where it has MOV AH 30 Int 21 CMP AX, 1e03 or whatever. (3.30) If the next line is JNZ . . . or JNE ...,, replace that with NOPs, or a JMP to the next instruction after the JNZ If the line is JZ or JE, . . . repace that with JMP OR, change the CMP AX, 1E03 to CMP Ax, 0002 IFF VER reports 2.00 DOS stores the major version number internally as a number which function 30 returns in AL, and a minor version number whigh it stores as if it had been a 2 digit decimal number returned in AH Therefore, your 3.30 is not 3 - 3 It is 3 - THIRTY Yes, 3.30 thinks that its version THIRTY of DOS 3! By removing or bypassing the comparison of version number, it will now NEVER give "INCORRECT DIS VERSION" DEBUG.COM will only run on the version of DOS that it shipped with unless you do the same patch. 'course how do you run DEBUG to patch DEBUG if it won't run until sfter you patch it? :-) -- Grumpy Ol' Fred cisin(a)xenosoft.com