3 ms·

Wow, this brings back memories of my final project for my "programming for Engineering students" course in the mid-80s. I wrote a DOS TSR program (remember tho

Wow, this brings back memories of my final project for my "programming for Engineering students" course in the mid-80s. I wrote a DOS TSR program (remember those?) which would pop up a window when you pressed a key sequence and present you with an ASM86 REPL. You could selectively 'save' pieces of code, and then when you exited the window, it would paste the saved code as inline assembly code (a hex byte array surrounded by some Turbo Pascal syntax) into your keyboard buffer - the assumption being that you are running the Turbo Pascal IDE, of course. The TSR itself was written in x86 assembly, which added a level of complexity. I would have given and arm and a leg to be able to do it in a high-level language like Ruby.

djmips 5y ago
Why not Turbo Pascal?
- lproven 5y ago
  I can only take a guess: that for a TSR on an early DOS PC, you really wanted it to be small. TSRs took a significant chunk of your base memory, and as you only got 640 kB of that, you wanted to save as much as you could. In the later days of DOS, programs grew so big that they wanted all of that 640 kB to themselves. Optional-extra type TSRs went out of fashion and DOS (first DR DOS 5, then MS played copy-cat with MS-DOS 5) gained built-in memory managers to load necessary TSRs (e.g. CD, mouse and keyboard drivers, disk cache, etc.) into Upper Memory Blocks. UMBs were a 386 thing: you used a 386 memory manager to map any unused bits of the I/O space in the PC's memory map (i.e. from 641 kB up to 1 MB) as RAM. Anything that wasn't being used for ROM or memory-mapped I/O, you could put RAM there and then load TSRs into these little chunks of RAM -- 1 or 2 dozen kB of RAM each. https://en.wikipedia.org/wiki/Upper_memory_area https://en.wikipedia.org/wiki/Upper_memory_area Yes, we were that desperate for base memory. It didn't matter if you had 2 or 4 or 16MB of RAM, DOS could only run programs in the 1st 1 MB of it, and only freely use the first ⅓ of that first meg. All the rest could only be used for data, disk caches, and other non-executable stuff. A side-effect of having a 386 memory manager, for real DOS power users, was that fancy 3rd party ones like Quarterdeck QEMM could also offer multitasking. Quarterdeck sold a tool called DESQview that let you run multiple DOS programs side-by-side and switch between them -- radical stuff in the 1980s. But once you had that, you didn't need TSRs any more.

djmips 5y ago

Why not Turbo Pascal?

lproven 5y ago
I can only take a guess: that for a TSR on an early DOS PC, you really wanted it to be small. TSRs took a significant chunk of your base memory, and as you only got 640 kB of that, you wanted to save as much as you could. In the later days of DOS, programs grew so big that they wanted all of that 640 kB to themselves. Optional-extra type TSRs went out of fashion and DOS (first DR DOS 5, then MS played copy-cat with MS-DOS 5) gained built-in memory managers to load necessary TSRs (e.g. CD, mouse and keyboard drivers, disk cache, etc.) into Upper Memory Blocks. UMBs were a 386 thing: you used a 386 memory manager to map any unused bits of the I/O space in the PC's memory map (i.e. from 641 kB up to 1 MB) as RAM. Anything that wasn't being used for ROM or memory-mapped I/O, you could put RAM there and then load TSRs into these little chunks of RAM -- 1 or 2 dozen kB of RAM each. https://en.wikipedia.org/wiki/Upper_memory_area https://en.wikipedia.org/wiki/Upper_memory_area Yes, we were that desperate for base memory. It didn't matter if you had 2 or 4 or 16MB of RAM, DOS could only run programs in the 1st 1 MB of it, and only freely use the first ⅓ of that first meg. All the rest could only be used for data, disk caches, and other non-executable stuff. A side-effect of having a 386 memory manager, for real DOS power users, was that fancy 3rd party ones like Quarterdeck QEMM could also offer multitasking. Quarterdeck sold a tool called DESQview that let you run multiple DOS programs side-by-side and switch between them -- radical stuff in the 1980s. But once you had that, you didn't need TSRs any more.