C: hex dump application

A C version of PrintHex to avoid a dependency on Mono.

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C: Hello, World!

gcc (GCC) 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

Java: generating a DOS executable

By incrementally changing instructions in an assembly language, it is possible to build up a picture of how the bytes relate to the assembly instructions (without going to the trouble of actually reading the documentation). Note that, for these trivial examples at least, there is no difference between the binaries generated by NASM and the equivalent MS Debug instructions.

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Assembler: Hello, World! [2]

NASM version 0.98.39 compiled on Feb 25 2005
DOS, 16bit, x86

;syntax expected by NASM
;DOS, x86, 16bit
org 100h        ;start at address 100
mov ax,0200h    ;AH=2
mov dx,0048h    ;'H'
int 21h         ;int 21,2 (print char)
mov dx,0065h    ;'e'
int 21h
mov dx,006Ch    ;'l'
int 21h
mov dx,006Ch    ;'l'
int 21h
mov dx,006Fh    ;'o'
int 21h
mov dx,002Ch    ;','
int 21h
mov dx,0020h    ;' '
int 21h
mov dx,0057h    ;'W'
int 21h
mov dx,006Fh    ;'o'
int 21h
mov dx,0072h    ;'r'
int 21h
mov dx,006Ch    ;'l'
int 21h
mov dx,0064h    ;'d'
int 21h
mov dx,0021h    ;'!'
int 21h
int 20h         ;int 20 (terminate)

Compare and contrast with the debug.exe version.

Assembler: using debug.exe to write DOS programs

C:\WINDOWS\system32\debug.exe

Windows (XP) still comes with Debug.

C:\test>DEBUG
-a
0C8A:0100 mov ax,0200
0C8A:0103 mov dx,0041
0C8A:0106 int 21
0C8A:0108 int 20
0C8A:010A
-h 010A 0100
020A  000A
-n PCHAR.COM
-rcx
CX 0000
:000A
-w
Writing 0000A bytes
-q

C:\test>PCHAR.COM
A

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Assembler: Hello, World!

DOS, x86, 16bit, debug.exe

mov ax,0200
mov dx,0048
int 21
mov dx,0065
int 21
mov dx,006C
int 21
mov dx,006C
int 21
mov dx,006F
int 21
mov dx,002C
int 21
mov dx,0020
int 21
mov dx,0057
int 21
mov dx,006F
int 21
mov dx,0072
int 21
mov dx,006C
int 21
mov dx,0064
int 21
mov dx,0021
int 21
int 20