; Version	: 1.1
; Updated	: 2/7/2020
; Description	: NextChar program. Quite slowly fills up a buff in static memory with a char, a space and then the next char etc
; License	: GPLv3+

;; static memory is nicer to use than the stack
section .bss
	buff resb 257 ;space for 128 characters + 128 spaces + newline
	bufflen equ $-buff

section .text
global _start

_start:
mov eax,0x0	;start character
mov ecx,128	;number of times to print
xor ebx,ebx	;counter register for position in Buff

loop:
mov byte[buff+ebx],al	;The character in eax is copied to Buff (very slow)
mov byte[buff+ebx+1],' ';A space is copied after the character

inc eax		;go to next ASCII character
add ebx,2	;Add 2 to ebx, so it now points to after the space

dec ecx		;deincrement ecx since we just copied a character
test ecx,ecx	;test if ecx is zero
jnz loop	;jump to loop to copy the next character if ecx is not zero

mov byte[buff+ebx-1],0xA	;add the newline (-1 overwrites the last space)

mov eax,1	;sys_write
mov edi,1	;fd = STDOUT_FILENO
mov edx,bufflen ;num of bytes to print
mov rsi,buff	;where the characters are located
syscall

Exit:
mov eax,60	;code for sys_exit
xor edi,edi	;Return value of 0
syscall		;Do sys_exit