As I am still new on this message board, I will share some stuffs in Assembly , for example, the screenshot below demonstrate DEBUG program can create .COM executable in a few steps. (H.COM actually print a 'H' character on screen)

DEBUG isn't included in DOSBox. I either get it from FreeDOS project or download it as separate package from the Internet (somewhere, can't remember).

Does the DEBUG remind you of the old days?

com format is plain file, so it always easy to make one as it contain no header.

as for debug, IIRC tomasz said in live stream this is a retro programming

I began programming in x86 back in the 80286 days, and debug was my only assembler. I wrote batch files to pipe text into debug and save/run the output. The rapid iteration paradigm is still my favorite way to learn. Getting more feedback from your tools means solving errors as they happen or shifting design to match working models. Even HLLs have adopted this approach through incremental building - reducing the turnaround time for even the most complex of projects.

I am new to this, it sounds like a nice trick. Can you please share how do I use batch files to pipe text into debug?

Many of the operations still exist today in other forms. These pages do a better job explaining the details:

https://ss64.com/nt/syntax-redirection.html
https://datacadamia.com/lang/dos/redirection ...is the TLDR

The general technique is called redirection and is very powerful: small tools can be chained together to create a powerful mesh of functionality.

I found a collection of 4 very old dos utilities (*.scr files in the archive) which used debug.com (prior ms dos 5.0) / debug.exe (since ms dos 5.0) to create .com executable, they are only plane files with hexadecimal code, but for some there is also *.asm source code included obtained by reversing binaries and disassembling them. Unfortunately the disasm is for a86 assembler, they are dated back into 1998...

Anyone remember AFD debugger? It was next step after DEBUG utility.

I used afd some times, my version is dated back into 1985, if anyone needs it just let me know. I also used td.exe Turbo Debugger from Borland Turbo Assembler package.

The first assembly programs I typed, were debug listings from the Australian Personal Computer magazine. I believe I had an XT system that time. I had always wanted to learn assembly/Machine Language, but didn't have a reference book. I remember looking at the cryptic mnemonics of the listing, but I didn't understand what it did. I know that I wanted to write my own "debug" programs.

A little later, I got an assembler, and didn't have to use debug. I did once play with debug at work, making a small .COM file, just for the fun of it, to see if I could.