CP String

STRING
IN C PROGRAMMING
1
Strings
• A string is nothing but the collection of the individual array elements
or characters.
• String is enclosed within Double quotes.
• “programming" is a example of String.
• Each Character Occupy 1 byte of Memory.
• Size of “programming“ = 11 bytes
• String is always Terminated with NULL Character (‘\0′).

char word[20] = “‘p’ , ‘r’ , ‘o’ , ‘g’ , ‘r’ , ‘a’ , ‘m’ , ‘m’ , ‘I’ , ‘n’ , ‘g’ , ‘\
0’” 2
NULL Character
• NULL Character is also known as string terminating
character.
• It is represented by “\0”.
• NULL Character is having ASCII value 0
• NULL terminates a string, but isn’t part of it
• important for strlen() – length doesn’t include the NULL
3
Declaration of a string
• Since we cannot declare string using String Data Type, instead
of
which we use array of type “char” to create String.
• Syntax :
• char String_Variable_name [ SIZE ] ;
• Examples :
• char city[30];
• char name[20];
4
Rules for declaring a string
• String / Character Array Variable name should be legal C Identifier.
• String Variable must have Size specified.
• char city[];
• Above Statement will cause compile time error.
• Do not use String as data type because String data type is included in
later languages such as C++ / Java. C does not support String data type
• When you are using string for other purpose than accepting and
printing data then you must include following header file in your code–
5
#include<string.h>
Initializing String (Character Array)
• Process of Assigning some legal default data to String is Called
Initialization of String.
• A string can be initialized in different ways. We will explain this
with the help of an example.
• Below is an example to declare a string with name as str and
initialize it with “GeeksforGeeks”.
1. char str[] = "GeeksforGeeks";
2. char str[50] = "GeeksforGeeks";
3. char str[] = {'G','e','e','k','s','f','o','r','G','e','e','k','s','\0'};
4. char str[14] = {'G','e','e','k','s','f','o','r','G','e','e','k','s','\0'};
6
STRING
#include <stdio.h>
EXAMPLE
int main () {
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
printf("Greeting message: %s\n", greeting );
return 0; }
When the above code is compiled and executed, it produces

the following result −
Greeting message: Hello

Functions of string.h
Function Purpose Example Output
Strcpy(); Makes a copy of a string strcpy(s1, “Hi”); Copies “Hi” to ‘s1’

variable
Strcat(); Appends a string to the strcat(“Work”, “Hard”); Prints “WorkHard”
end of another string
Strcmp(); Compare two strings strcmp(“hi”, “bye”); Returns -1.

alphabetically
Strlen(); Returns the number of strlen(“Hi”); Returns 2.
characters in a string
Strrev(); reverses a given string Strrev(“Hello”); olleH

Strlwr(); Converts string to Strlwr(“HELLO”); hello
lowercase
Strupr(); Converts string to Strupr(“hello”); HELLO
uppercase
String Copy (strcpy)
• strcpy( ) function copies contents of one string into another string.
• Syntax : strcpy (destination_string , source_string );
• Example:-strcpy ( str1, str2) – It copies contents of str2 into str1.

strcpy ( str2, str1) – It copies contents of str1 into str2.
• If destination string length is less than source string, entire source string
value won’t be copied into destination string. For example, consider
destination string length is 20 and source string length is 30. Then, only 20
characters from source string will be copied into destination string and
remaining 10 characters won’t be copied and will be truncated.
String Concat (strcat)
• strncat( ) function in C language concatenates (appends) portion of one
string at the end of another string.
• Syntax : strncat ( destination_string , source_string, size);
• Example:-strncat ( str2, str1, 3 ); – First 3 characters of str1 is

concatenated at the end of str2.
• As you know, each string in C is ended up with null character (‘\0’).
• In strncat( ) operation, null character of destination string is overwritten

by source string’s first character and null character is added at the end
of new destination string which is created after strncat( ) operation. 10
String Compare (strcmp)
 strcmp( ) function in C compares two given strings and returns zero if they
are same.
 If length of string1 < string2, it returns < 0 value that is -1.
 If length of string1 > string2, it returns > 0 value that is 1
 If length of string1 = string2 it returns 0.
Syntax : strcmp (str1 , str2 );strcmp( ) function is case sensitive. i.e, “A” and
“a” are treated as different characters.
11
String Length (strlen)
• strlen( ) function in C gives the length of the given
string.
• Syntax : strlen(str);
• strlen( ) function counts the number of characters in a given

string and returns the integer value.
• It stops counting the character when null character is found. Because,

null character indicates the end of the string in C.
12
THANK YOU
13

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STRING

• String is enclosed within Double quotes.

• “programming" is a example of String.

• Each Character Occupy 1 byte of Memory.

• Size of “programming“ = 11 bytes

• String is always Terminated with NULL Character (‘\0′).

• NULL Character is having ASCII value 0

• NULL terminates a string, but isn’t part of it

• important for strlen() – length doesn’t include the NULL

• char String_Variable_name [ SIZE ] ;

• String Variable must have Size specified.

• Above Statement will cause compile time error.

char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};

printf("Greeting message: %s\n", greeting );

When the above code is compiled and executed, it produces

Greeting message: Hello

Strcpy(); Makes a copy of a string strcpy(s1, “Hi”); Copies “Hi” to ‘s1’

Strcmp(); Compare two strings strcmp(“hi”, “bye”); Returns -1.

Strrev(); reverses a given string Strrev(“Hello”); olleH

• Syntax : strcpy (destination_string , source_string );

• Example:-strcpy ( str1, str2) – It copies contents of str2 into str1.

• Syntax : strncat ( destination_string , source_string, size);

• Example:-strncat ( str2, str1, 3 ); – First 3 characters of str1 is

• As you know, each string in C is ended up with null character (‘\0’).

• In strncat( ) operation, null character of destination string is overwritten

 If length of string1 > string2, it returns > 0 value that is 1

 If length of string1 = string2 it returns 0.

• strlen( ) function counts the number of characters in a given

• It stops counting the character when null character is found. Because,

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