Infix To Postfix | Using Stack | With Simple code

Conventional notation is called infix notation. The arithmetic operators appears between two operands. Parentheses are required to specify the order of the operations. For example: a + (b * c). Post fix notation (also, known as reverse Polish notation) eliminates the need for parentheses. There are no precedence rules to learn, and parenthese are never needed. Because of this simplicity, some popular hand-held calculators use postfix notation to avoid the complications of multiple sets of parentheses. The operator is placed directly after the two operands it needs to apply. For example: a b c * +

  //write a program in c to convert Infix to Postfix
  #include <stdio.h>
  #include <ctype.h>
  char stack[100];
  int top = -1;
  void push(char x)
  {
    stack[++top] = x;
  }
 char pop()
   {
    if (top == -1)
        return -1;
    else
        return stack[top--];
  }
  int priority(char x)
  {
    if (x == '(')
        return 0;
    if (x == '+' || x == '-')
        return 1;
    if (x == '*' || x == '/')
        return 2;
    return 0;
}
int main()
{
    char exp[100], *e,x;
    printf("Enter the expression:\n ");
    scanf("%s ", exp);
    printf("\n");
    e = exp;
    printf(" Postfix is :  ");
    while (*e != '\0')
    {
        if (isalnum(*e))
            printf("%c", *e);
        else if (*e == 'c')
            push(*e);
        else if (*e == ')')
        {
            while ((x = pop())!= '(')
                printf("%c", x);
        }
        else
        {
            while (priority(stack[top] >= priority(*e)))
                printf("%c", pop());
            push(*e);
        }
        e++;
    }
    while (top != -1)
    {
        printf("%c", pop());
    }
    return 0;
  }

When the above program is executed, it produces following results --<\b>
OUTPUT NO : - 01

Enter the expression:
(a+b+c)+d 

 Postfix is :  abc++d+

Enter the expression:
 ((a+b)+(c/d)+(E+F))/(G+H)*K

 Postfix is :  ab+cd/EF+++GH+K*/