Your First Program

The following examples demonstrate how to write a simple “Hello, world!” program.

• Windows:

  Source code:

  .import kernel32.dll GetStdHandle
  .import kernel32.dll WriteFile
  
  .data
  msg:
      .ascii "Hello, world!\r\n"
  written:
      dd 0
  
  .text
  _start:
      sub rsp, 40
  
      mov rcx, -11
      call GetStdHandle
  
      mov rcx, rax
      lea rdx, [rip + msg]
      mov r8, 15
      lea r9, [rip + written]
      mov qword [rsp + 32], 0
      call WriteFile
  
      add rsp, 40
      mov rax, 0
      ret
  

  Running the program:

  # Using the JIT compiler:
  rasm run main.s
  
  # Using AOT compilation:
  rasm build main.s
  
  ./main
  

• Linux: Source code:

  _start:
      jmp print
  
  msg:
      .ascii "Hello, world!\n"
  
  print:
      mov rax, 1
      mov rdi, 1
      lea rsi, [rip + msg]
      mov rdx, 14
      syscall
  
      mov rax, 60
      xor rdi, rdi
      syscall
  

  The program is built and executed in the same way as on Windows.

• macOS:

  Examples for macOS will be added after the Mach-O backend has been fully tested.

Why is the code different?

On Windows, output is performed using the WinAPI because direct system calls are not considered a stable user-space programming interface.

On Linux, output is performed using the write system call.