![]() ![]() However, a few years ago when I wrote Ur-Scheme, I did do this for lambda expressions: the code for the lambda expression is generated inline in the middle of its containing code, which then has to contain a jump past it. data, so that if your compiler does this, you still don't have to insert JMP instructions. Gas lets you switch back and forth between. You can also imagine that a compiler might be somewhat simpler if it generated code in the order in which it encountered the expressions. Maybe someone had this habit in their assembly and adapted it to the 8086's calling convention by inserting MOVs and a JMP instruction? Rather than, say, mov $3, %rdi mov $4, %rsi call atan2. It seems sort of intuitive to do things this way if you're writing atan2(3, 4), it's nice to be able to translate this to Mark Smotherman explains this in more detail, using PDP-8-compatible syntax, in. So the code to call FOO with arguments 1 and 2 would be (in Intel syntax) So, the callee would indirect from the "return address" stored in FOO to retrieve its arguments, incrementing the return address after each one. They would put them after the JMS instruction in the caller. I was surprised when he told me how people normally passed arguments. That is why we put checksums for each version of the file so that you can. Remember, your browser may display a message saying that the downloaded file may be dangerous. To download the file, use the 'Download' button. So to return, the called subroutine would do an indirect jump using the address stored in the memory word before the beginning of its code. To download the file click the 'I am not a robot' box. The PDP-8 didn't have a stack to call a subroutine, the JMS FOO instruction would store the return address at (the effective address computed from) FOO, then continue execution at the following word. Thank you for the nice comment!Ī friend of mine used to program the PDP-8 a lot. I have now updated the GitHub repository with this updated source code and binary. Here is a complete example that moves the string to the bottom and saves two bytes: Calls program with as first parameter the configuration file. I believe I picked up the style of having the string at the top and jumping over it from other similar code I had come across in those days. Since I was still learning the x86 CPUs, the intention here was not to save bytes but instead to have something working. That chance encounter helped me to dive into the world of assembly language programming much before the coursework introduced me to more popular assemblers. DOSBox 0.74 on Windows and Linux DEBUG.EXE from Windows XP copied to DOSBox DEBUG.EXE from various versions of MS-DOS will cause problem including unexpected. Turned out it was available on any standard installation of MS-DOS as well as Windows 98. While browsing the C:\Windows directory, I fortuitously happened to discover the DEBUG.EXE program. However, if the executable you are trying to run fails almost immediately or runs quickly and exits then you could try the following steps: Set a debug point at the start of the code. Find your process created by running your executable and click 'attach'. I was still learning microprocessors back then. In VS navigate to Debug -> Attached to Process. I happened to stumble upon it today in my archives and thought of sharing it on GitHub. I will get back to your question regarding my progress in another post.I wrote this about 20 years ago during my university days. Online documentation can be rather lengthy and abstract. Being able to write a short assembly language program and immediately executing it is a very useful way to see what a instruction does. Does the DOSBox debugger allow you to feed it a few instructions and execute them? Like Debug? The reason I am messing with Debug is because I realized my knowledge of the specifics on some instructions was lacking. I am only interested in realmode 8086 instructions as the games I have been trying to analyze don't need anything more. I got Debug to work by installing a full MS-DOS 6.22 installation onto a harddisk image. (the debugger is rarely changed and there is a dosbox-current build available)ītw: did you get any further with your Alley Cat analyse ![]() There is no need for that - use the dosbox internal debugger (way more easier): builds are available here: DOSBox debuggerĪnd "no" you don't need to build from source yourself if even the antiqued debug.exe seems to fit your needs □ - beware the internal dosbox debugger is also started with "debug " on
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