String is a sequence of characters terminated with a null character \0 at the end.

How to declare strings

Declaring string is similar to one-dimensional character array. Below is the syntax:

char var-name[size];

How to initialize strings

Strings can be initialized in a number of ways:

char str[] = "OneCompiler";

char str[20] = "OneCompiler";

char str[] ={'O','n','e','C','o','m','p','i','l','e','r','\0'};

char str[20] ={'O','n','e','C','o','m','p','i','l','e','r','\0'}

How to read strings from console

#include <stdio.h>
int main()
{
    char str[20];
    scanf("%s", str); // to read the string values from stdin
    printf("You have entered: %s", str); // to print the sting
    return 0;
}

Check Result here

Consider if you have given One Compiler as input in the stdin. Surprisingly you get One alone as output. That is because a white space is present between One and Compiler. So how can you read a entire line which also has white spaces in it.

Consider your input string is Hello Everyone.. Happy Learning!!

#include <stdio.h>
int main()
{
    char str[50];
    fgets(str, sizeof(str), stdin);  // to read string from stdin
    printf("You entered: ");
    puts(str);    // to print entire string
    return 0;
}

Check Result here

String Functions

C has various in-built string functions which can manipulate null-terminated strings.

Function name	Description
strlen(str)	to return the length of string str
strcat(str1, str2)	to concatenate string str2 onto the end of string str1.
strcpy(str1, str2)	To copy string str2 into string str1.
strcmp(str1, str2)	returns 0 if str1 and str2 are the same and less than 0 if str1 < str2 and a positive number if str1 > str2
strchr(str, c)	Returns a pointer to the first occurrence of character c in string str
strstr(str1, str2)	Returns a pointer to the first occurrence of string str2 in string str1

Examples

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

int main () {

   char str1[20] = "Happy";
   char str2[20] = "learning";
   char str3[20];
   char str4[20] = "learning";
   char str[50] = "Hello world, learning is fun.";

   int  length, cmp , cmp1 ;
   int *ptr, * ptr1;  
   
   length = strlen(str1); // to find length of a string
   printf("length of string is :  %d\n", length );
   
   strcat( str1, str2); // concatenates str1 and str2 
   printf("Concatenation of str1 and str2:   %s\n", str1 );

   strcpy(str3, str1); // to copy a string into another
   printf("string copy of str1 to str3 :  %s\n", str3 );

   cmp = strcmp(str2,str4); // to compare two strings
   printf("string compare result :  %d\n", cmp );
   
   
   cmp1 = strcmp(str1,str4); // to compare two strings
   printf("string compare result :  %d\n", cmp1 );
   
   ptr = strchr(str1, 'p'); // usage of strchr
   printf("pointer to the first occurrence of p in string Happy :  %d\n", ptr );
   
   ptr1 = strstr(str, str2); // usage of strstr
   printf("pointer to the first occurrence of str2 in str :  %d\n", ptr1 );
   

   return 0;
}

Check result here