When I pop the stack code below, the value does not return properly.

#include <stdio.h>
#include <stdlib.h>
#define MAX_STACK_SIZE   5
void stackFull() {
    fprintf(stderr, "Stack is full, cannot add element");
    exit(1);
}
void stackEmpty() {
    fprintf(stderr, "Stack is Empty");
    exit(1);
}
void push(char *a, char stack[], int *top)
{
    if (*top >= MAX_STACK_SIZE - 1)
        stackFull();
        stack[++*top] = *a;  
}
char pop(char *a, char *stack, int *top)
{
    if(*top==-1)
        stackEmpty();
    return stack[*top--];
}
void showStack(char *stack, int top)
{
    int i;
    if (top == 0) printf ("No value stored in the stack").\n");
    else {
        printf ("List of values stored in the stack\n");
        for (i = 0; i < top + 1; i++) {
            printf("%03d : %c\n", i + 1, stack[i]);
        }
        printf("%d values are stored.\n", top);
    }
}
void main()
{
    int select = 0;
    char a;
    int top = -1;             
    char stack[MAX_STACK_SIZE]; 

    while (select != 4) {
        printf("\n1. Put value in stack\n");
        printf("2. Pull value from stack\n");
        printf("3. Check the value stored in the stack\n");
        printf("4. Exit program\n\n");
        printf ("Enter : ");
        scanf_s("%d", &select); 
        getchar();
        switch (select) {
        case 1: 
            printf("Enter a value to save: ");"
            a=getchar();
            push(&a, stack, &top);
            break;
        case 2: 
            pop(&a, stack, &top);
            printf("Import -> %c", a);
            break;
        case 3: 
            showStack(stack, top);
            break;
        }
    }
}