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Assembly language with NASM gives you direct, human-readable control over the machine at the instruction level. This environment targets 32-bit x86 assembly assembled with the Netwide Assembler (NASM) 2.15.5. You write mnemonics like mov, add, and int that map closely to processor instructions, manage registers and memory explicitly, and invoke the operating system through software interrupts and the Linux system-call interface.
Programs are organized into sections such as .text for code and .data for initialized data, with execution beginning at the _start label. On 32-bit Linux, system calls are made with int 0x80, passing the call number in eax and arguments in ebx, ecx, edx, and so on. Writing in assembly teaches how registers, the stack, and calling conventions actually work beneath higher-level languages.
main.asm is the entry point for each run.
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section .data
msg db "Hello, World!", 0x0A
len equ $ - msg
section .text
global _start
_start:
mov eax, 4 ; sys_write
mov ebx, 1 ; stdout
mov ecx, msg
mov edx, len
int 0x80
mov eax, 1 ; sys_exit
xor ebx, ebx
int 0x80section .text
global _start
_start:
mov eax, 1 ; sys_exit
mov ebx, 42 ; exit code
int 0x80section .text
global _start
_start:
mov eax, 2
add eax, 3 ; eax = 5
mov ebx, eax ; use result as exit code
mov eax, 1 ; sys_exit
int 0x80section .text
global _start
_start:
mov ecx, 5 ; loop 5 times
xor eax, eax ; accumulator
next:
add eax, ecx
loop next ; dec ecx, jump while ecx != 0
mov ebx, eax ; sum 5+4+3+2+1 = 15
mov eax, 1 ; sys_exit
int 0x80section .text
global _start
_start:
mov eax, 7
cmp eax, 10
jl less ; jump if eax < 10
mov ebx, 1
jmp done
less:
mov ebx, 0
done:
mov eax, 1 ; sys_exit
int 0x80section .data
ch db 'A', 0x0A
section .text
global _start
_start:
mov eax, 4 ; sys_write
mov ebx, 1 ; stdout
mov ecx, ch
mov edx, 2 ; char + newline
int 0x80
mov eax, 1 ; sys_exit
xor ebx, ebx
int 0x80section .text
global _start
_start:
mov eax, 6
mov ebx, 7
imul ebx ; edx:eax = eax * ebx -> 42
mov ebx, eax ; exit code = 42
mov eax, 1 ; sys_exit
int 0x80section .bss
buf resb 64 ; reserve 64 bytes
section .text
global _start
_start:
mov byte [buf], 'X'
mov byte [buf+1], 0x0A
mov eax, 4 ; sys_write
mov ebx, 1 ; stdout
mov ecx, buf
mov edx, 2
int 0x80
mov eax, 1 ; sys_exit
xor ebx, ebx
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Assembly (NASM) is one of 46 single-file compiler scratchpads. Each run submits only main.asm; local sibling-file imports are not enabled.
Linked-project languages (23): Node.js, TypeScript, Deno, Python, C, Go, Dart, Swift, Rust, Ruby, PHP, Java, Kotlin, C++, C#, Nim, Crystal, Haxe, Zig, Scala, D, Bun, Objective-C.
Single-file scratchpads (46): Matplotlib, NumPy, pandas, Haskell, Clojure, Perl, Lua, Tcl, jq, Raku, Elixir, Bash, Zsh, Nushell, R, Assembly (NASM), Julia, Octave, Groovy, PowerShell, Visual Basic .NET, Odin, Pascal, Lisp, Erlang, CoffeeScript, COBOL, BASIC, V, Racket, OCaml, Prolog, AWK, Emacs Lisp, Emojicode, Forth, F#, Fortran, Assembly (NASM64), Solidity, Mojo, Ada, WASM (WAT), Gleam, Shell Script (sh), Scheme.
Download file exports the active Assembly (NASM) source file.