String Handling in C: Character Arrays and String Functions

In C, strings are not a distinct data type but exist as character arrays. Understanding how to use character arrays and related string functions is crucial for writing effective C programs. This article will provide a detailed overview of string handling in C, including the definition and initialization of character arrays, as well as commonly used string functions.

1. Basic Concepts of Strings

In C, a string is composed of a series of characters and is terminated by a null character (<span>'\0'</span>). A simple example is as follows:

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

Here, <span>str</span> is a character array containing 13 elements (12 visible characters plus one null character).

1.1 Strings vs. Regular Arrays

While we can treat strings as regular one-dimensional arrays, they have some special characteristics:

• Strings must be terminated with <span>'\0'</span> to identify their end.
• Standard library functions can be used to manipulate these strings.

2. Definition and Initialization of Strings

2.1 Definition Methods

We can define and initialize a string in several ways:

// Method 1: Direct assignment
char str1[] = "Hello";
// Method 2: Assigning one character at a time
char str2[6]; // Note: space for '\0' must be reserved
str2[0] = 'H';
str2[1] = 'e';
str2[2] = 'l';
str2[3] = 'l';
str2[4] = 'o';
str2[5] = '\0'; // Manually adding the terminator

2.2 Important Considerations

• When defining, ensure enough size is allocated to accommodate all characters and the terminator.
• If declared but not initialized, for example, <span>char str3[10];</span>, the contents of this array are uninitialized and may contain garbage values.

3. Common String Functions

The C standard library provides several useful functions for handling and manipulating strings. These functions are declared in <span><string.h></span>. Below are some commonly used functions along with example code:

3.1 <span>strlen()</span>

Calculates the length of a string, excluding the terminator.

#include <stdio.h>
#include <string.h>
int main() {
    char str[] = "Hello";
    printf("Length of string: %lu\n", strlen(str)); // Output: Length of string: 5
    return 0;
}

3.2 <span>strcmp()</span>

Compares two strings; returns 0 if equal, a negative number if the first is less than the second, and a positive number if greater.

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

3.3 <span>strcpy()</span>

Copies the source string to the destination, including the terminator.

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

3.4 <span>strcat()</span>

Concatenates two strings, appending the source to the destination and automatically adding the terminator.

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

Conclusion

This article introduced important concepts regarding how to handle and manipulate strings in C, including how to define, initialize, and use various functions from the standard library. Mastering these foundational concepts is crucial for further learning of more complex data structures and algorithms. Practicing these topics in actual programming will help you better understand them. I hope this article is helpful for your learning.