Strings in C

A string in C is a sequence of characters terminated by a null character '0'. Strings are used to represent text in C programming, and they are implemented as arrays of characters. Strings are widely used for tasks like input/output, text processing, and data manipulation.

Definition

A string in C is an array of characters that is terminated by the special character '0' to indicate the end of the string. Strings can be manipulated using string handling functions like strlen(), strcpy(), strcat(), etc.

String Declaration and Initialization

In C, strings can be declared in two ways:

• Using character arrays.
• Using string literals enclosed in double quotes.

                
char str1[20];  // Declaration of character array
char str2[] = "Hello, World!";  // Initialization with a string literal
                
            

Example: Declaring and Printing a String

This example demonstrates how to declare a string and print it using the printf() function.

                
#include <stdio.h>
int main()
{
    char str[] = "Hello, C World!";
    printf("String: %s\n", str);  // Using %s to print the string
    return 0;
}
                
            

String Length

In C, the length of a string can be calculated using the strlen() function, which counts the number of characters in the string excluding the null character '0'.

                
#include <stdio.h>
#include <string.h>
int main() 
{
    char str[] = "Hello, C!";
    int length = strlen(str);  // strlen() function calculates string length
    printf("Length of string: %d\n", length);
    return 0;
}
                
            

String Manipulation Functions

C provides several functions to manipulate strings. Below are some common string functions:

• strcpy(destination, source): Copies the source string into the destination string.
• strcat(destination, source): Concatenates (appends) the source string to the destination string.
• strcmp(str1, str2): Compares two strings and returns 0 if they are equal, a positive value if str1 is greater, and a negative value if str1 is smaller than str2.


• strchr(str, character): Returns a pointer to the first occurrence of the specified character in the string.
• strstr(str, substring): Finds the first occurrence of a substring within a string.

Example: Using strcpy and strcat

This example demonstrates the use of strcpy() and strcat() functions to copy and concatenate strings.

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

Key Points

• Strings in C are arrays of characters terminated by the null character '0'.
• String manipulation functions like strcpy(), strcat(), and strcmp() are part of the C Standard Library.
• To determine the length of a string, use the strlen() function, which excludes the null terminator.
• When dealing with strings, ensure that there is enough space in the array to store the string and the null character.
• Always terminate strings with '0' to avoid undefined behavior.