Stack Implementation Using Array PUSH, POP ,PEEP,CHANGE and DISPLAY in C

				
					#include<stdio.h>
#define size 5
struct stack{
   int a[size],top;
   int temp[size], tos;
}s;
// Push operation....
void push(int item){
        s.a[++s.top] = item;
}
// Pop operation....
int pop(){
    return s.a[s.top--];
}
// Display operation....
void display(){
    int i;
    printf("\nThe stack contains: ");
    for(i = s.top; i>=0; i--){
        printf("\n\t%d", s.a[i]);
    }
}
// Peep operation....
void peep(){
    printf("\n\tTop : %d", s.top);
    printf("\n\tValue: %d",s.a[s.top]);
}
void change(int row, int new_element){
    int i;
    int j = -1;
    printf("\n\tTop: %d", s.top);
    for(i=s.top; i>row; i--){
        s.temp[++j] = s.a[s.top--];
   /*
        display();
        printf("\n\tTop: %d", s.top);
        printf("\n\t j : %d", j);
   */
    }
    s.a[s.top] = new_element;
    /*
        display();
        printf("\n\tTop: %d", s.top);
        printf("\n\t j : %d", j);
    */
    for(i = j; i>-1; i--){
        s.a[++s.top] = s.temp[j--];
    /*
        display();
        printf("\n\tTop: %d", s.top);
        printf("\n\t j : %d", j);
    */
    }
}

int main(){
    s.top = -1;
    int item, choice, row, new_element;
    char ans;
    do{
        printf("\n-----------------------------");
        printf("\nSTACK IMPLEMENTATION PROGRAM\n");
        printf("-----------------------------");
        printf("\n     1. Push\n     2. Pop\n     3. Display\n     4. Peep\n     5. Change\n     6. Exit\n");
        printf("-----------------------------\n");
        printf("\n  Enter your choice: ");
        scanf("%d", &choice);
        switch(choice){
        case 1:
            if(s.top >= size-1){
                 printf("\nStack overflow..\n");
                 break;
            }
            printf("\nEnter item to be pushed:  ");
            scanf("%d", &item);
            push(item);
            break;
        case 2:
            if(s.top == -1){
                printf("\n..Stack underflow..\n");
                break;
            }
            pop();
            break;
        case 3:
            display();
            break;
        case 4:
            peep();
            break;
        case 5:
            printf("\n\tEnter row no : ");
            scanf("%d",&row);
            printf("\n\tEnter new element: ");
            scanf("%d", &new_element);
            change(row, new_element );
            break;
        case 6:
            return 0;
        }
    }while(choice != 6);

    return 0;
}