C String

As a group of an integer is called as integer array. Similarly, a group of character is called as character array. A character array is known as String.

For example:

• Each character occupies one byte of memory.
• And the last character is always \0.
• ‘\0’ is called a null character.
• ASCII value of ‘\0’ is zero.
• %s is a format specifier use to print a string.

The following figure shows the way a character array is stored in memory.

The elements of the character array are stored in contiguous memory locations. The terminating null \0 is important.

The above example can also be initialized as,

In this declaration \0 is not necessary. C compiler automatically inserts a null character.

Example:

Output:

Program:

Output:

Points to remember:

• char a[5]="hello"; //error

  1	char a[5]="hello";   //error

  Because given length is not sufficient for given string.
  Actual length of string is 6 (hello(5) + ‘\0′(1) =6). Therefore above initialization is not valid. Hence correct initialization is:

  char a[6]="hello";

  1	char a[6]="hello";

• Name of the array itself is a constant pointer.
  So it cannot be incremented nor decremented.
  char a[6] = "hello"; a++; //error

  1 2	char a[6] = "hello"; a++;             //error

Standard Library String Functions:

Every C compiler has many sets of useful string handling functions. There are many important string functions defined in “string.h” library. The following list contain commonly used string functions:

1. strlen
2. strrev
3. strlwr
4. strupr
5. strcat
6. strncat
7. strcpy
8. strncpy
9. strcmp
10. strncmp
11. strcmpi
12. stricmp
13. strnicmp
14. strdup
15. strchr
16. strrchr
17. strstr
18. strset
19. strnset

From the above list of functions strlen(), strcpy(), strcat(), strcmp() are the most commonly used functions.
Let us study these functions one by one.