initial commit

1 files changed, 39 insertions, 0 deletions

diff --git a/nextchar.asm b/nextchar.asm
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index 0000000..5538a1b
--- /dev/null
+++ b/nextchar.asm
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+; Version	: 1.0
+; Updated	: 17/6/2020
+; Description	: NextChar program. Quite slowly fills up a buff in static memory with a char, a space and then the next char etc
+
+;; static memory is nicer to use than the stack
+section .bss
+	Buff resb 52 ; space for 26 characters + 25 spaces + newline
+
+section .text
+global _start
+
+_start:
+mov eax,'a'	;start character
+mov ecx,26	;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 newline)
+
+mov eax,1	;sys_write
+mov edi,1	;fd = STDOUT_FILENO
+mov edx,52  	;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