Program 9 - Evaluation of Postfix Expression

	#include <stdio.h>
	int stack[100];
	int top = -1;
	//(a+b)*(c+d)
	//ab+cd+*
	int evaluate(char postfix[]){
	int i, op1, op2, temp;
	char ch;
	for(i = 0; postfix[i] != '\0'; i++){
	ch = postfix[i];
	if(isdigit(ch)){
	stack[++top] = ch - '0';
	} else if(isalpha(ch)){
	printf("Enter value of %c: ", ch);
	scanf("%d", &temp);
	stack[++top] = temp;
	} else if(ch == '+' || ch == '-' || ch == '*' || ch =='/'){
	op2 = stack[top--];
	op1 = stack[top--];
	switch(ch){
	case '+':
	stack[++top] = op1 + op2;
	break;
	case '-':
	stack[++top] = op1 - op2;
	break;
	case '*':
	stack[++top] = op1 * op2;
	break;
	case '/':
	stack[++top] = op1 / op2;
	break;
	}
	}
	}
	return stack[top--];
	}
	int main(){
	char postfix[20];
	printf("Enter postfix expression: ");
	gets(postfix);
	printf("The evalutaion of the given expression is: \n%d",evaluate(postfix));
	}