Day 5.md

day	title	description
5	Strings and Pointers	Covering String declaration, String handling functions, Pointer definiton, declaration,usage and pointer arithmetic

Day 5 - Strings and Pointers in C

Strings in C

String Handling Functions

Strings in C are arrays of characters terminated by a null character (\0).

Array of Characters

To declare and initialize a string:

char str[] = "Hello, World!";

Or:

char str[50] = "Hello, World!";

Standard Library Functions

strlen

Calculates the length of a string.

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

int main() {
    char str[] = "Hello, World!";
    printf("Length: %zu\n", strlen(str));
    return 0;
}

strcpy

Copies one string to another.

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

int main() {
    char src[] = "Hello, World!";
    char dest[50];
    strcpy(dest, src);
    printf("Copied String: %s\n", dest);
    return 0;
}

strcmp

Compares two strings.

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

int main() {
    char str1[] = "Hello";
    char str2[] = "World";
    int result = strcmp(str1, str2);
    if(result == 0) {
        printf("Strings are equal\n");
    } else {
        printf("Strings are not equal\n");
    }
    return 0;
}

strcat

Concatenates two strings.

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

int main() {
    char str1[50] = "Hello";
    char str2[] = ", World!";
    strcat(str1, str2);
    printf("Concatenated String: %s\n", str1);
    return 0;
}

Pointers

Definition

A pointer is a variable that stores the memory address of another variable.

Declaration

To declare a pointer:

int *ptr;

Usage

Pointers are used to store and manage the addresses of other variables.

Example

#include <stdio.h>

int main() {
    int var = 10;
    int *ptr = &var;

    printf("Value of var: %d\n", var);
    printf("Address of var: %p\n", &var);
    printf("Value stored in ptr: %p\n", ptr);
    printf("Value pointed to by ptr: %d\n", *ptr);

    return 0;
}

Pointer Arithmetic

You can perform arithmetic operations on pointers to navigate through an array.

Example

#include <stdio.h>

int main() {
    int arr[] = {10, 20, 30, 40, 50};
    int *ptr = arr;

    for(int i = 0; i < 5; i++) {
        printf("Value at ptr[%d]: %d\n", i, *(ptr + i));
    }

    return 0;
}

Pointers and Arrays

Pointers can be used to manipulate arrays.

Example

#include <stdio.h>

void printArray(int *arr, int size) {
    for(int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int size = sizeof(arr) / sizeof(arr[0]);

    printArray(arr, size);

    return 0;
}

Pointers to Pointers

A pointer to a pointer is a form of multiple indirection, or a chain of pointers.

Example

#include <stdio.h>

int main() {
    int var = 10;
    int *ptr = &var;
    int **pptr = &ptr;

    printf("Value of var: %d\n", var);
    printf("Value pointed to by ptr: %d\n", *ptr);
    printf("Value pointed to by pptr: %d\n", **pptr);

    return 0;
}