# High School Mathematics Extensions/Mathematical Programming/Exercise 1: The Complete Program

## Explanation

Program for looking at integer division and modulus.

## Code to change

Add and replace the following code:
//includes
#include <stdio.h>
#include <conio.h>
//type definitions
#define TRUE 1
#define FALSE 0

//function prototypes
void init();
void input_message();
char input();
char retrieve_keypress();
char validate(char check_me);
void execute_command(char command);
void output_divide();
void output_modulus();
void output_values();
int get_integer();

//global variables
unsigned char done;
int r;
int l;

//function definitions
void init()
{
done=FALSE;
r=5;
l=2;
}
void input_message()
{
cprintf("Key      Action.\n");
cprintf("/        Display r/l = result.\n");
cprintf("%%        Display r%%l = result.\n");
cprintf("=        Display r=value, l=value.\n");
cprintf("r or R   Set the value for r.\n");
cprintf("l or L   Set the value for l.\n");
cprintf("x or X   End program.\n");
}
char input()
{
{
cprintf("\nInvalid Command.\n");
input_message();
}
}
int get_integer()
{
int ret_val;
char lastpress;

cprintf("Enter integer: ");
cscanf("%i",&ret_val);
lastpress=getch();
cprintf("\n");
return ret_val;
}
char retrieve_keypress()
{
char ret_val;
ret_val=getche();
cprintf("\n");
return ret_val;
}
char validate(char check_me)
{
char ret_val=0;
switch (check_me)
{
case '/':
case '%':
case '=':
case 'r':
case 'R':
case 'l':
case 'L':
case 'x':
case 'X':   ret_val++;
break;
}
return ret_val;
}
void execute_command(char command)
{
switch (command)
{
case '/':   output_divide();
break;
case '%':   output_modulus();
break;
case '=':   output_values();
break;
case 'r':
case 'R':   r=get_integer();
output_values();
break;
case 'l':
case 'L':   l=get_integer();
output_values();
break;
case 'x':
case 'X':   done=TRUE;
break;
}
}
void output_divide()
{
if (r > 0)
{
cprintf("%d / %d = %d.\n",l,r,l/r);
}
else
{
cprintf("l = %d, r = %d. Please set r to a value other than 0.\n",r,l);
}
}
void output_modulus()
{
if (r > 0)
{
cprintf("%d %% %d = %d.\n",l,r,l%r);
}
else
{
cprintf("l = %d, r = %d. Please set r to a value other than 0.\n",r,l);
}
}
void output_values()
{
cprintf("l = %d, r = %d.\n",l,r);
}
void main()
{
char command;
init();
input_message();
while(done!=TRUE)
{
command=input();
execute_command(command);
}
}