NASM Coding: More Programs

6. ; A program that prints a simple pyramid of stars ('*') to stdout.
   
   section .bss
       maxlines  equ 8
       dataSize  equ 44
       output:   resb dataSize
   
   section .text
       global _start
   
   _start:
       mov rdx, output             ; rdx = pointer to buffer
       mov r8, 1                   ; current line length
       xor r9, r9                  ; stars written in current line
   
   line:
       mov byte [rdx], '*'         ; write '*'
       inc rdx                     ; advance pointer
       inc r9                      ; increment count
   
       cmp r9, r8                  ; reached line length?
       jne line                    ; if not, continue line
   
   lineDone:
       mov byte [rdx], 10          ; newline '\n'
       inc rdx
   
       inc r8                      ; next line length++
       xor r9, r9                  ; reset star counter
   
       cmp r8, maxlines
       jle line                    ; continue if r8 <= maxlines
   
   done:
       ; write(stdout, output, dataSize)
       mov rax, 1                  ; sys_write
       mov rdi, 1                  ; stdout
       mov rsi, output             ; buffer
       mov rdx, dataSize           ; size
       syscall
   
       ; Exit
       mov rax, 60                 ; sys_exit
       xor rdi, rdi
       syscall