96. Implement Stack Using Array with Push and Pop Operations

#include <stdio.h>
#include <stdint.h>
#include <string.h>

#define MAX 10

void process_stack(int n) {
    // Your logic here
    int stack[MAX];
    int top = -1;

    char cmd[10];
    int val;

    for (int i = 0; i < n; i++) {
        scanf("%s", cmd);

        if (strcmp(cmd, "push") == 0) {
            scanf("%d", &val);
            if (top >= MAX - 1) {
                printf("Stack Overflow\n");
            } else {
                stack[++top] = val;
            }
        } else if (strcmp(cmd, "pop") == 0) {
            if (top == -1) {
                printf("Stack Underflow\n");
            } else {
                printf("%d\n", stack[top--]);
            }
        }
    }
}

int main() {
    int n;
    scanf("%d", &n);
    getchar(); // Consume newline after number

    process_stack(n);
    return 0;
}

Why Stacks Matter in Firmware?

• Used for state rollback, parsing, undo systems
• Avoids malloc; deterministic memory behavior
• Basis of function call stacks in low-level systems

Logic Summary

• Use top variable to track the last used index
• Push: increment top, insert element 
• Pop: read and decrement top