InfixtoPostfix

#include<stdio.h>
#include<String.h>
#define MAX 100

char stack[MAX];
int top = -1;

void push(char x)
{
    stack[++top]= x;
}
char pop()
{
    if(top == -1)
        return -1;
    else
    {
        return stack[top--];
    }
}

int prc(char x)
{
    if(x =='(')
        return 0;
    else if(x == '^')
        return 3;
    else if(x =='*' || x =='/' || x=='%')
        return 2;
    else if(x =='+' || x =='-')
        return 1;
}

int isChar(char x)
{
    if(x>='A' && x<='Z')
        return 1;
    else
        return 0;
}

int main()
{
    char exp[MAX];
    char *ptr,data;
    int i;

    printf("\n Enter Exp. =");
    scanf("%s",exp);
    ptr=exp;
    while(*ptr!='\0')
    {
        if(isChar(*ptr)==1)
            printf("%c",*ptr);
        else if(*ptr=='(')
            push(*ptr);
        else if(*ptr==')')
        {
            while(1)
                {
                    data = pop();
                    if(data == '(' )
                        break;
                    printf("%c",data);
                }
        }
        else
        {
            while(prc(stack[top]) >= prc(*ptr))
            {
                data = pop();
                printf("%c",data);
            }
            push(*ptr);
        }
        ptr++;
    }
    while(top!= -1)
    {
        data = pop();
        printf("%c",data);
    }
    return 0;
}