Strings Concatenation in C

To concatenate (combine) two strings in C, you can use the strcat function or manually iterate through the characters in the strings and copy them to a new string. Here’s how to do it using both methods:

Using strcat Function:

The strcat function is a standard library function in C that concatenates (appends) one string to another. Here’s an example:

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

int main() {
    char str1[100] = "Hello, ";
    char str2[] = "world!";

    strcat(str1, str2); // Concatenate str2 to the end of str1

    printf("Concatenated string: %s\n", str1);

    return 0;
}

In this program:

• We declare two character arrays, str1 and str2, to hold the strings we want to concatenate.
• We use the strcat function from the <string.h> library to concatenate str2 to the end of str1.
• Finally, we print the concatenated string.

Manual Concatenation (Iterating through Characters):

You can also concatenate strings manually by iterating through the characters in the source string and copying them to the destination string. Here’s an example:

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

int main() {
    char str1[100] = "Hello, ";
    char str2[] = "world!";
    char concatenated[200]; // Create a new string to store the concatenated result

    int i, j;

    // Copy str1 to concatenated
    for (i = 0; str1[i] != '\0'; i++) {
        concatenated[i] = str1[i];
    }

    // Concatenate str2 to concatenated
    for (j = 0; str2[j] != '\0'; j++) {
        concatenated[i + j] = str2[j];
    }

    concatenated[i + j] = '\0'; // Null-terminate the concatenated string

    printf("Concatenated string: %s\n", concatenated);

    return 0;
}

In this manual concatenation example:

• We declare two character arrays, str1 and str2, to hold the strings we want to concatenate, and a new character array concatenated to store the concatenated result.
• We use i and j as loop counters.
• We copy str1 to concatenated by iterating through its characters and copying them one by one.
• We then concatenate str2 to concatenated in a similar manner by iterating through its characters.
• Finally, we add a null terminator '\0' at the end of the concatenated string to ensure it is properly terminated.

Both methods will result in the concatenation of the strings. Choose the one that suits your needs and coding style.