stdio example added

x86_64/1_stdio.asm

@@ -0,0 +1,51 @@
+global _start
+
+section .data
+  str: db "Please give me a string: " ; \n = 0xA
+
+  strSize: equ $ - str
+  ; $ = current assembler address.
+  ; Since str is all that is above it must be the size
+
+  stdin: equ 0 ; POSIX
+  stdout: equ 1 ; POSIX
+
+; Uninitialized space goes here, pretty much your heap of uninitialized bytes
+; for all kinds of purposes
+section .bss
+  strBuffer: resb 64 ; reserve 64 bytes
+  strBufferSize: equ 64 ; same as above
+
+; This is where the code goes. Text. Makes sense, right?
+section .text
+_start:
+  ; x64 has the syscall function, in contrast to int in x86 and ARM
+
+  ; Write to stdout
+  mov rax, 1
+  mov rdi, stdout  ; fd to write to
+  mov rsi, str     ; pointer
+  mov rdx, strSize ; size
+  syscall ; all arguments are specified above! (x86 = int 0x80)
+
+  ; Read from stdin
+  xor rax, rax ; 0
+  mov rdi, stdin     ; fd to read from
+  mov rsi, strBuffer ; where to store it
+  mov rdx, strBufferSize ; maximum number of bytes
+  syscall
+
+  ; syscall return codes are always stored in register A
+  ; The number of bytes read in was returned through this
+	mov rdx, rax
+
+	mov rax, 1
+	mov rdi, stdout
+	mov rsi, strBuffer
+	syscall
+
+
+  ; Exit routine
+  mov rax, 60 ; 60 is the exit routine
+  xor rdi, rdi ; our return code (0)
+  syscall