wcwr palindrome using stack

/****************************
 *  Umang B Bhatt            *
 *   bhatt.umang7@gmail.com  *
 *****************************/

/**
 * program for wcwr palindrome string
 */

#include<stdio.h>
#define MAX 100
#define TRUE 1
#define FALSE 0


int push(char *s, int top, char ele)
{

    int i;
    if (top >= MAX)
    {

        printf("\nStack Overflow");
    } else
    {
        s[++top] = ele;
    }

    return top;
}

int pop(char *a, int *top)
{

    if ((*top) >= 0)
    {
        (*top) = (*top) - 1;

        return a[(*top) + 1];
    } else
    {
        printf("Stack underflow\n");

        return 0;
    }
}

void main()
{
    int i;

    char a, b;
    char c[MAX];

    int valid = TRUE;
    int TOP = -1;

    char s[MAX];
    //remember that declraing the stack as global is not a good practice (according to my openion)
    printf("Enter string: ");
    gets(c);

    TOP = push(s, TOP, 'c');
    for (i = 0; c[i] != 'c'; i++) // you can modify this string as you want

    { // some people may modify to go upto n/2 etc
        TOP = push(s, TOP, c[i]);
    }


    i++;
    for (; c[i] != '\0'; i++)
    {

        if (TOP < 0)
        {
            valid = FALSE;

            break;
        } else
        {
            a = pop(s, &TOP);

            if (c[i] != a)
            {
                valid = FALSE;
            }
        }

    }

    if (TOP == 0)
    {
        a = pop(s, &TOP);

        if (a != 'c')
        {
            valid = FALSE;
        }
    } else

    {
        valid = FALSE;
    }
    if (valid == TRUE)
    {

        printf("Valid palindrome string\n");
    } else
    {
        printf("Invalid palindrome string\n");
    }
}