CS 456 - Systems Programming Spring 2024

Displaying ./code/mar27/helloNotes.c

#include <stdio.h>
#include <unistd.h>

int main(){

	write(1, "Hello World!\n", 13); 
	
	/*
	 *
	 * In NASM Assembly, the above would like this:
	 *
	 *   mov     edx, 13   // number of bytes to write, third argument in write
   	     mov     ecx, msg  // buffer, second argument in write
    	     mov     ebx, 1    // file descriptor, first argument in write
             mov     eax, 4    // opcode for write
             int     80h
	 *
	 *  write in C  is structured like this
	 *
	 *  write( file descriptor, the buffer with the text, how many bytes to write)
	 *   
	 *   and write returns number of bytes sucessfully written
	 *
	 *   write has the opcode of 4 in 32 bit assembly
	 *
	 *   eax - where the opcode (or what system call you are using goes)
	 *
	 *    write takes three arguments, they go in ebx ecx and edx respectively 
	 *
	 *   ebx - file descriptor, first argument
	 *   ecx - string buffer, the second argument
	 *   edx - number of bytes to write, third argument
	 *
	 *
	 * /



}