C Strings

Strings in C are one-dimensional arrays of characters terminated by a null character '\0'. They are used to store and manipulate sequences of characters such as words or sentences in C programming.

Syntax

To declare a string without initialization:

char string_name[];

To declare and initialize a string using a string literal:

char string_name[] = "text";

To declare and initialize a string character by character (must include \0 at the end):

char string_name[size] = {'c', 'h', 'a', 'r', 's', '\0'};

Strings in C are declared using the char data type, followed by the string name and square brackets []. String values can be initialized in two ways:

• Zero or more characters, digits, and escape sequences surrounded in double quotes.
• An array of comma-separated characters, surrounded in curly brackets {}, and ending with a null character '\0'.

Note: The null character '\0' is important as it marks the end of the string.

Example: String Declaration

The following declaration and initialization create a string of “Howdy”:

char message[6] = {'H', 'o', 'w', 'd', 'y', '\0'};

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Even though “Howdy” has only 5 characters, message has 6 characters due to the null character at the end of the array.

The above statement can be rewritten as:

char message[] = "Howdy";

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Memory Representation

Here’s how a string is stored in memory:

Displaying a String

To display a string in C, the printf() function from the stdio.h header file can be used along with the %s format specifier:

#include <stdio.h>
int main() {
  char message[] = "Hi y'all!";
  printf("Bot: %s\n", message);
  return 0;
}

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This code produces the following output:

Bot: Hi y'all!

String Functions

The string.h header defines several string functions for manipulating arrays of characters:

• strchr() - Finds the first occurrence of a given character.
• strcmp() - Compares two strings and returns an integer value.
• strcpy() - Copies one string into another string.
• strlen() - Returns the length of the string, excluding the terminating null character.
• strtok() - Breaks a string into a series of tokens using a list of delimiters.

Frequently Asked Questions

1. How many types of strings are there in C?

In C, there is only one type of string: a null-terminated array of characters. However, strings can be implemented in two ways:

• As character arrays (e.g., char str[10] = "Hello";)
• As character pointers (e.g., char *str = "Hello";)

2. What is the main difference between Java strings and C strings?

The main differences between Java strings and C strings are:

• Java strings are objects of the String class, while C strings are character arrays
• Java strings are immutable, while C strings can be modified
• Java strings have built-in methods like length(), concat(), while C strings require external functions from libraries like string.h
• Java handles memory management automatically, while C requires manual memory allocation and deallocation for dynamic strings
• Java strings don’t need a terminating character, but C strings must end with the null character '\0'

3. What is a string literal in C?

A string literal in C is a sequence of characters enclosed in double quotes (e.g., "Hello") that represents a string constant. When a string literal appears in code, it is stored in read-only memory with an automatically appended null character '\0' at the end. String literals cannot be modified, and attempting to modify them results in undefined behavior.