queue_array.c

#include <stdio.h>

char queue[256];

int last = -1;
int limit = 256;

void enqueue(char itemToInsert) {
    if (last == limit - 1) {
        printf("Queue Overflow");
        return;
    }
    last = last + 1;
    queue[last] = itemToInsert;
}

void dequeue() {
    if (last == -1) {
        printf("Queue Underflow");
        return;
    }
    for(int i = 0; i < last; ++i) {
        queue[i] = queue[i + 1];
    }
    last -= 1;

}

void main() {
    enqueue('a');
    enqueue('b');
    enqueue('c');
    enqueue('d');
    enqueue('e');
    enqueue('f');
    printf("\n\nADDED ITEMS");
    for(int i = 0; i <= last; ++i) {
        printf("\n%c", queue[i]);
    }

    dequeue();
    printf("\n\nREMOVED FIRST ITEM");
    for(int i = 0; i <= last; ++i) {
        printf("\n%c", queue[i]);
    }
}

stack_array.c

#include <stdio.h>

char stack[256];

int last = -1;
int limit = 256;

void push(char itemToInsert) {
    if (last == limit - 1) {
        printf("Stack Overflow");
        return;
    }
    last = last + 1;
    stack[last] = itemToInsert;
}

void pop() {
    if (last == -1) {
        printf("Stack Underflow");
        return;
    }
    stack[last] = NULL;
    last = last - 1;
}

void main() {
    push('a');
    push('b');
    push('c');
    push('d');
    push('e');
    push('f');
    printf("\n\nADDED ITEMS");
    for(int i = 0; i <= last; ++i) {
        printf("\n%c", queue[i]);
    }

    push();
    printf("\n\nREMOVED LAST ITEM");
    for(int i = 0; i <= last; ++i) {
        printf("\n%c", queue[i]);
    }
}