Arrays and Strings in C

Arrays and strings are fundamental data structures in C programming. Arrays store collections of elements of the same type, while strings are essentially arrays of characters ending with a null terminator (\0).

1. Introduction to Arrays

An array is a collection of elements of the same data type stored in contiguous memory locations.

a. Declaring an Array

To declare an array, specify the data type, array name, and size in square brackets.

Syntax

data_type array_name[size];

Example

#include <stdio.h>
 
int main() {
    int numbers[5]; // Declares an integer array with 5 elements
    numbers[0] = 10; // Assigns value to the first element
    numbers[1] = 20; // Assigns value to the second element
 
    printf("First element: %d\n", numbers[0]);
    printf("Second element: %d\n", numbers[1]);
 
    return 0;
}

b. Initializing an Array

You can initialize an array at the time of declaration.

Example

#include <stdio.h>
 
int main() {
    int numbers[5] = {10, 20, 30, 40, 50}; // Array initialization
 
    for (int i = 0; i < 5; i++) {
        printf("Element %d: %d\n", i, numbers[i]);
    }
 
    return 0;
}

2. Multidimensional Arrays

A multidimensional array is an array of arrays. The most common multidimensional array is the two-dimensional array, which can be thought of as a matrix.

a. Declaring a Two-Dimensional Array

Syntax

data_type array_name[rows][columns];

Example

#include <stdio.h>
 
int main() {
    int matrix[2][3] = {{1, 2, 3}, {4, 5, 6}}; // 2x3 matrix
 
    // Printing matrix elements
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 3; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
 
    return 0;
}

b. Multidimensional Array Example

You can have arrays of more than two dimensions.

Example

#include <stdio.h>
 
int main() {
    int cube[2][2][2] = {
        {{1, 2}, {3, 4}},
        {{5, 6}, {7, 8}}
    };
 
    // Accessing elements of a 3D array
    printf("cube[1][0][1]: %d\n", cube[1][0][1]);
 
    return 0;
}

3. String Handling Functions

Strings in C are arrays of characters that end with a null terminator (\0). C provides several string-handling functions to manipulate strings.

a. strlen() - String Length

The strlen() function returns the length of the string (excluding the null terminator).

Example

#include <stdio.h>
#include <string.h>
 
int main() {
    char str[] = "Hello, World!";
    printf("Length of the string: %lu\n", strlen(str));
 
    return 0;
}

b. strcpy() - String Copy

The strcpy() function copies a string from the source to the destination.

Example

#include <stdio.h>
#include <string.h>
 
int main() {
    char src[] = "Hello";
    char dest[20];
 
    strcpy(dest, src);
    printf("Copied string: %s\n", dest);
 
    return 0;
}

c. strcmp() - String Comparison

The strcmp() function compares two strings lexicographically. It returns 0 if they are equal, a positive value if the first string is greater, and a negative value if the second string is greater.

Example

#include <stdio.h>
#include <string.h>
 
int main() {
    char str1[] = "Apple";
    char str2[] = "Banana";
 
    int result = strcmp(str1, str2);
 
    if (result == 0) {
        printf("Strings are equal.\n");
    } else if (result < 0) {
        printf("str1 is less than str2.\n");
    } else {
        printf("str1 is greater than str2.\n");
    }
 
    return 0;
}

d. strcat() - String Concatenation

The strcat() function appends the source string to the destination string.

Example

#include <stdio.h>
#include <string.h>
 
int main() {
    char str1[20] = "Hello";
    char str2[] = ", World!";
 
    strcat(str1, str2);
    printf("Concatenated string: %s\n", str1);
 
    return 0;
}

Diagram of Arrays and Strings in C

Summary of Arrays and Strings in C

• Arrays: Collections of elements of the same data type, stored in contiguous memory locations.
  • Single-dimensional arrays store data in a linear form.
  • Multidimensional arrays store data in a grid-like structure.
• Strings: Arrays of characters ending with a null terminator (\0).
  • String Handling Functions:
    • strlen(): Calculates string length.
    • strcpy(): Copies one string to another.
    • strcmp(): Compares two strings lexicographically.
    • strcat(): Concatenates two strings.

Arrays and strings are essential for handling collections of data and text manipulation in C.

Key Points:

• Arrays allow storing collections of similar data types.
• Strings are essentially arrays of characters with special handling.
• String handling functions make manipulating strings easier.