C Strings

In C, a string is an array of characters that ends with a null character (\0). String functions are used to manipulate strings, such as copying, concatenating, comparing, and searching.

Declare a String

char str[SIZE];

where SIZE is the maximum number of characters that can be stored in the string.

Initialize a String

char str[] = "Hello World";


char str[SIZE] = "Hello World";

Access individual Characters in a String

char c = str[index];

where index is the position of the character in the string, starting from 0.

Some common string functions that can be used in C are:

  • strcpy(dest, src): Used for copying one string to another.
  • strcat(dest, src): Used for concatenating two strings.
  • strlen(str): Used for finding the length of a string.
  • strcmp(str1, str2): Used for comparing two strings.


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

int main() {
   char str1[20] = "Hello";
   char str2[20] = "World";
   char str3[20];
   // Copying string str1 to str3
   strcpy(str3, str1);
   printf("str3 after strcpy(): %s\n", str3);
   // Concatenating string str1 and str2
   strcat(str1, str2);
   printf("str1 after strcat(): %s\n", str1);
   // Finding the length of string str1
   int len = strlen(str1);
   printf("Length of str1: %d\n", len);
   // Comparing string str1 and str2
   int cmp = strcmp(str1, str2);
   printf("Result of strcmp(): %d\n", cmp);
   return 0;

This program will display the following output:

str3 after strcpy(): Hello
str1 after strcat(): HelloWorld
Length of str1: 10
Result of strcmp(): 1

String functions are an important tool for processing and manipulating text in a program. They can be used to implement string algorithms, parsing, and formatting, among other things.

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