or : Alex Lazellari.
# Creation Date : 31/10/2018
# Description : A program that calculate the greatest common divisor.
#
# Registers used:v0,a0,t0,t1,t2,t3,zero.
#v0 : From expression evaluation and function results.
#a0 : Four parameters for subroutine.
#t0 : Contains the value of the first integer of the user.
#t1 : Contains the value of the second integer of the user.
#t2 : Contains the result of the t1 mod t2.
#t3 : Contains user's guest ,about the G.C.D..
#zero : zero register is used in conditions.
#
.data
    message0 : .asciiz "Welcome USER, this program calculates the greatest common divisor of two integers and challenge you to find it. \nLet's start..!\n"
    message1 : .asciiz "Enter the first integer : "
    message2 : .asciiz "Enter the second integer : "
    #complex message--------------------
    message3 : .asciiz "\nWho is the greatest common divisor between "
    message4 : .asciiz " and "
    message5 : .asciiz " ?\nEnter value : "
    #-----------------------------------
    message6 : .asciiz "\nWrong! Try again."
    message7 : .asciiz "Who is the greatest common divisor ?\nEnter value : "
    message8 : .asciiz "\nExcellent you have found the right answer!."
.text
.globl __start
__start:
    #Here the program prints the messge0.
    li $v0,4
    la $a0,message0
    syscall
    #print (“ Give an integer: ”);
    li $v0,4
    la $a0,message1     #The program prints the message1.
    syscall
    #a = Read_Integer();
    li $v0,5            #The program read the first integer.
    syscall
    move $t0,$v0
    #print (“ Give an integer: ”);
    li $v0,4
    la $a0,message2     #The program prints the message2.
    syscall
    #b = Read_Integer();
    li $v0,5            #The program read the second integer.
    syscall
    move $t1,$v0
    #complex message.
    #print (“ Who is the GCD of “+ a + “ and “ + b + “? ”);
    li $v0,4
    la $a0,message3
    syscall             #The program prints the message3.
    li $v0,1
    move $a0,$t0
    syscall             #The program prints the a variable.
    li $v0,4
    la $a0,message4
    syscall             #The program prints the message4.
    li $v0,1
    move $a0,$t1
    syscall             #The program prints the b variable.
    li $v0,4
    la $a0,message5
    syscall             #The program prints the message 5.
    #---------------------------------------
#Here the program calculate the G.C.D.
    #y = a % b;
    rem $t2,$t0,$t1
    #while (y!=0){
    #   a=b;
    #   b=y;
    #   y=a%b;
    #}
calculation:
    beq  $t2,$zero,exit     #The condition. If true then exit else
    move $t0,$t1            #the value of t1 goes to t0,
    move $t1,$t2            #value of t2 goes to t1
    rem  $t2,$t0,$t1        #and result of t0 mod t1 is the value of