Mega Code Archive
A simple four-function calculator
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#include <stdio.h>
#include <stdlib.h>
#define MAX 100
int *p; /* will point to a region of free memory */
int *tos; /* points to top of stack */
int *bos; /* points to bottom of stack */
void push(int i)
{
if(p > bos) {
printf("Stack Full\n");
return;
}
*p = i;
p++;
}
int pop(void)
{
p--;
if(p < tos) {
printf("Stack Underflow\n");
return 0;
}
return *p;
}
int main(void)
{
int a, b;
char s[80];
p = (int *) malloc(MAX*sizeof(int)); /* get stack memory */
if(!p) {
printf("Allocation Failure\n");
exit(1);
}
tos = p;
bos = p + MAX-1;
printf("Four Function Calculator\n");
printf("Enter 'q' to quit\n");
do {
printf(": ");
gets(s);
switch(*s) {
case '+':
a = pop();
b = pop();
printf("%d\n", a+b);
push(a+b);
break;
case '-':
a = pop();
b = pop();
printf("%d\n", b-a);
push(b-a);
break;
case '*':
a = pop();
b = pop();
printf("%d\n", b*a);
push(b*a);
break;
case '/':
a = pop();
b = pop();
if(a==0) {
printf("Divide by 0.\n");
break;
}
printf("%d\n", b/a);
push(b/a);
break;
case '.': /* show contents of top of stack */
a = pop();
push(a);
printf("Current value on top of stack: %d\n", a);
break;
default:
push(atoi(s));
}
} while(*s != 'q');
return 0;
}
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