C Pointers Demo

c-pointers-demo.c

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

// demonstrate pointer basics
void pointerBasics() {
    int a = 42;
    int *ptr = &a;

    printf("Pointer Basics:\n");
    printf("Address of a: %p\n", (void*)&a);
    printf("Value of ptr: %p\n", (void*)ptr);
    printf("Value pointed by ptr: %d\n", *ptr);
}

// demonstrate dynamic memory allocation
void dynamicMemoryAllocation() {
    int *array = (int*)malloc(5 * sizeof(int));
    if (array == NULL) {
        fprintf(stderr, "Memory allocation failed\n");
        return;
    }

    printf("\nDynamic Memory Allocation:\n");
    for (int i = 0; i < 5; i++) {
        array[i] = i * 10;
        printf("array[%d] = %d (Address: %p)\n", i, array[i], (void*)&array[i]);
    }

    free(array);
}

// demonstrate pointer arithmetic
void pointerArithmetic() {
    int array[5] = {10, 20, 30, 40, 50};
    int *ptr = array;

    printf("\nPointer Arithmetic:\n");
    for (int i = 0; i < 5; i++) {
        printf("ptr + %d points to %d (Address: %p)\n", i, *(ptr + i), (void*)(ptr + i));
    }
}

// demonstrate pointers to pointers
void pointersToPointers() {
    int a = 100;
    int *ptr = &a;
    int **pptr = &ptr;

    printf("\nPointers to Pointers:\n");
    printf("Address of a: %p\n", (void*)&a);
    printf("Value of ptr: %p\n", (void*)ptr);
    printf("Value of pptr: %p\n", (void*)pptr);
    printf("Value pointed by pptr: %p\n", (void*)*pptr);
    printf("Value pointed by *pptr: %d\n", **pptr);
}

// demonstrate string manipulation with pointers
void stringManipulation() {
    char str[] = "Hello, World!";
    char *ptr = str;

    printf("\nString Manipulation:\n");
    printf("Original string: %s (Address: %p)\n", str, (void*)str);

    while (*ptr != '\0') {
        printf("Character: %c (Address: %p)\n", *ptr, (void*)ptr);
        ptr++;
    }
}

// demonstrate use of function pointers
void functionPointerExample() {
    void (*funcPtr)(void) = pointerBasics;

    printf("\nFunction Pointer:\n");
    printf("Address of function pointer: %p\n", (void*)funcPtr);
    funcPtr();
}

int main() {
    pointerBasics();
    dynamicMemoryAllocation();
    pointerArithmetic();
    pointersToPointers();
    stringManipulation();
    functionPointerExample();

    return 0;
}