What Data Type Is a String in C?


Larry Thompson

When programming in C, it’s important to understand the various data types available. One commonly used data type is the string.

In C, a string is a sequence of characters enclosed in double quotes. It can contain letters, numbers, symbols, and even whitespace.

Declaring and Initializing Strings

To declare a string variable in C, you use the char keyword followed by the variable name. For example:

        char greeting[10];

The above code declares a string variable named “greeting” with a maximum size of 10 characters. It’s important to note that the size of the array should be large enough to accommodate the desired string length plus one extra character for the null terminator ‘\0’, which indicates the end of a string in C.

To initialize a string at declaration time, you can use either:

  • Static Initialization:
                char greeting[] = "Hello!";
  • Dynamic Initialization:
                strcpy(greeting, "Hello!");

The static initialization method assigns a constant value to the string variable directly. The dynamic initialization method uses the strcpy() function from the standard library to copy a given string into your declared variable.

Working with Strings

C provides several functions specifically designed for working with strings. Here are some commonly used functions:

  • strlen(): Returns the length of a string.
  • strcpy(): Copies one string to another.
  • strcat(): Concatenates two strings.
  • strcmp(): Compares two strings and returns a value indicating their relationship (e.g., equal, greater than, less than).

To use these functions, you’ll need to include the <string.h> header file at the beginning of your program.

Manipulating Strings

You can also manipulate strings directly by accessing individual characters using indices. In C, strings are zero-indexed, meaning the first character is at index 0. For example:

        printf("The first character of greeting is: %c\n", greeting[0]);

The above code prints the first character of the string variable “greeting”. You can also modify individual characters by assigning a new value to them. For example:

        greeting[0] = 'J';

The above code changes the first character of “greeting” to ‘J’.

The Null Terminator

In C, strings are null-terminated, which means they end with a null character ‘\0’. This is important because it allows C functions to determine where a string ends.

When declaring and initializing strings as shown earlier, C automatically adds the null terminator for you. However, when manipulating strings manually or using functions like strncpy(), you need to ensure that the last character is ‘\0’ to avoid unexpected behavior.


Strings are an essential data type in C and are used to store and manipulate sequences of characters. By understanding how to declare, initialize, and work with strings, you can effectively utilize them in your C programs. Remember the importance of the null terminator and familiarize yourself with the string manipulation functions provided by the <string.h> header file.

With this knowledge, you can confidently handle strings in your C programs!

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