mov  rax, 0x000F     ; Store the value 15 into the rax register
mov  rdi, rsi        ; Copy the value in the rsi register into the rdi register

lea  rdi, [message]  ; Load the address of [message] into the rdi register

push rcx             ; Push the value in the rcx register onto the top of the stack

pop  rcx             ; Pop the value off the top of the stack and into the rcx register

add  rdi, rsi        ; Add the value in rsi to rdi, and store the result in rdi
                     ; (i.e. rdi = rdi + rsi)

sub  rdi, rsi        ; Subtract the value in rsi from rdi, and store the result in rdi
                     ; (i.e. rdi = rdi - rsi)

inc  rax             ; Increment the value in rax by 1
                     ; (i.e. rax = rax + 1)

dec  rax             ; Decrement the value in rax by 1
                     ; (i.e. rax = rax - 1)

and  rdi, rsi        ; Bitwise AND, store result in rdi
                     ; (i.e. rdi = rdi & rsi)

or   rdi, rsi        ; Bitwise OR, store result in rdi
                     ; (i.e. rdi = rdi | rsi)

xor  rdi, rsi        ; Bitwise XOR, store result in rdi
                     ; (i.e. rdi = rdi ^ rsi)

not  rax             ; Bitwise Logical Not

shl  rax, 1          ; Shift left the bits in rax, padding the resulting empty bit positions with zeros

shr  rax, 1          ; Shift right the bits in rax, padding the resulting empty bit positions with zeros

cmp  rdi, rsi       ; Compare rdi and rsi (rdi - rsi) and set flags.
                    ; Similar to sub, but result is discarded.

test rdi, rsi       ; Compare rdi and rsi (rdi & rsi) and set flags.
                    ; Similar to and, but result is discarded.

cmp  rdi, rsi        ; Compare rdi and rsi
je   .label          ; Jump to .label if equal

call  label            ; Push return address and jump to label

ret                    ; Pop return address from stack and jump there

; ----------------------------------------------------------------------------------------
; Writes "Hello, World" to the console using only system calls. Runs on 64-bit macOS only.
; To assemble and run:
;
;     nasm -fmacho64 hello.asm
;     ld hello.o -static -o hello
;     ./hello
; ----------------------------------------------------------------------------------------

          global    start

          section   .text
start:    mov       rax, 0x02000004         ; system call for write
          mov       rdi, 1                  ; file handle 1 is stdout
          mov       rsi, message            ; address of string to output
          mov       rdx, 13                 ; number of bytes
          syscall                           ; invoke operating system to do the write

          mov       rax, 0x02000001         ; system call for exit
          mov       rdi, 0                  ; exit code 0
          syscall                           ; invoke operating system to exit


          section   .data
message:  db        "Hello, World", 10      ; note the newline at the end

; ----------------------------------------------------------------------------------------
; Prints the numbers 1-10 using the C library printf function. Runs on 64-bit macOS only.
; To assemble and run:
;
;     nasm -fmacho64 numbers.asm
;     ld -L /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib -lc -o numbers numbers.o
;     ./numbers
; ----------------------------------------------------------------------------------------

          global    _main
          extern    _printf
          default   rel


          section   .text
_main:
          mov       rcx, 1                  ; initialise the counter to 1

print_loop:
          ; Print the counter
          push      rcx                     ; caller - save register
          lea       rdi, [format]           ; set 1st parameter (format)
          mov       rsi, rcx                ; set 2nd parameter (current number)
          call      _printf                 ; call the C library printf function
          pop       rcx                     ; restore caller-saved register

          ; Increment the counter and loop while <= 10
          inc       rcx                     ; increment the counter
          cmp       rcx, 10                 ; compare the counter value to 10
          jle       print_loop              ; jump to print_loop if less then or equal to

          ; Exit the program
          mov       rax, 0                  ; set the exit code
          ret


          section   .data
format:   db        "%d", 10, 0             ; note the newline and NULL characters at the end

#include <stdio.h>

int main() {
  int i;
  for (i = 1; i <= 10; i++) {
    printf("%d\n", i);
  }
  return 0;
}

(1..10).each {|n| puts n }