Strings in C - A COMPLETE GUIDE OF COMPUTER NOTES

Strings in C are the collection of characters. Strings are also known as an “Array of Characters”.
Strings in C is a one-dimensional array.
Strings in C are ended by the “NULL” (‘\0’) character.

An array of Characters in C

Strings are written in double quotes (“Xcnotes”) while the character is written inside a single quote (‘X’).
In C programming, strings are not used as a data types (like char(for character), float(for decimal value like 6.78) , double(for decimal like 6.789), int(for integer value like 5,7) etc.).

Declaration of Strings in C

Strings are declared like an array(char your_name[20]) if you do not know what the arrays are? Then, first, you should read the arrays(User define, Non-primitive data type).

What is Array in C?

1. char str[5];

If we write char as “str[5]” then 5 bytes of memory are reserved for ‘str’.

2. char str[ ];

If we write char as “str[ ]” then the memory is allocated at the time of the program’s execution.

Initialization of Strings in C

Strings in C can be initialized in many ways,

Way 1

char str[8] = “Xcnotes”;

char str[ ] = “Xcnotes”;

In the above initialization, NULL (‘\0’) character is automatically inserted at the end of the string.

Way 2

char str[8] = {‘X’, ‘C’, ‘N’, ‘O’, ‘T’, ‘E’, ‘S’, ‘\0’};

char str[ ] = {‘X’, ‘C’, ‘N’, ‘O’, ‘T’, ‘E’, ‘S’, ‘\0’};

str[0]	str[1]	str[2]	str[3]	str[4]	str[5]	str[6]	str[7]
X	C	N	O	T	E	S	\0

Representation of String

Representation of string in a one-dimensional form

str[0]	str[1]	str[2]	str[3]	str[4]	str[5]	str[6]	str[7]
X	C	N	O	T	E	S	\0
2000	2001	2002	2003	2004	2005	2006	2007

Representation of string in a one-dimensional form

2000

Address

A string variable ‘str’ always holds the base address of a character array. It is also known as internal pointers.

C program in which a string is declared and printed.(String in C Example)

#include <stdio.h>

int main()

{

char str[8]=”Program”;

char str1[8] = {‘P’,’r’,’o’,’g’,’r’,’a’,’m’,’\0′};

printf (“String Literal is : %s\n”, str);

printf (“Character array is :%s\n”, str1);

return 0;

}

Read String from the user in C

‘Scanf’ function is used to read strings in C from the user.

‘Scanf’ function reads strings continuously until whitespace occurs.

Example

#include <stdio.h>

int main()

{

char str[10];

printf (“Enter String”);

scanf (“%s”, str);

printf (“String is %s\n”, str);

return 0;

}

If whitespace is given in the input then scanf will read the string coming from the first whitespace. You can read this in the given program below,

#include <stdio.h>

int main()

{

char str[30];

printf (“Enter String”);

scanf (“%s”, str);

printf (“String is %s\n”, str);

return 0;

}

If you want to read strings given with whitespace, then use the gets ( ) function and this function is available in ‘stdio.h’ header file.

C program gets() and puts() function

#include <stdio.h>

int main()

{

char str[30];

printf (“Enter String\n”);

gets (str);

printf (“string is %s \n”, str);

return 0;

}

puts( ) function is used to print the output on the screen.

#include <stdio.h>

#include <conio.h>

int main()

{

char str[10];

printf (“Enter string\n\t”);

gets(str);

puts(str);

return 0;

}

Library String Functions in C with Example

‘String.h’ header file consists of lots of library function like, strlen( ), strcpy( ), strcmp( ), strcat(), strrev( ) etc.

strlen	Use for Find the length of the String(xcnotes (6 lengths)
strcat	Appends 2 strings(Concat 2 strings)
strcpy	Copy the string
strcmp	Compare 2 strings
strrev	Reverse the string(SETONCX)
strupr	Convert string into Upper case(XCNOTES)
strlwr	Convert the string into Lower case(xcnotes)

library String Functions in C

Strlen() function in C

Strlen ( ): This function calculates the length of string excluding null (‘\0’) character.

Syntax:

Strlen (Name_of_string);

Program to calculate the length of the Strings in C

#include <stdio.h>

#include <string.h>

int main()

{

int length;

char str[]=”XCNOTES”;

length = strlen(str);

printf (“Length of string is = %d\n”,length);

return 0;

}

Output

The length of the string is 7

Strcat() Function in C

Strcat( ): This function connects two strings together.

Syntax

strcat (string1, string2);

Program to concatenates two strings in C.

#include <stdio.h>

#include <string.h>

int main()

{

char str1[]=”Xcnotes”;

char str2[]=”.co”;

strcat(str1,str2);

printf(“Concatenate string is %s”, str1);

return 0;

}

Output

Concatenate String is Xcnotes.co

Strcmp() function in C

strcmp ( ): This function compares two strings. If the two strings are equal then it returns 0 otherwise it returns 1.

Syntax

strcmp (string1, string2);

When string1 is greater than string2, then it returns 1.

When string1 is less than string2, then it returns -1.

If string1 and string2 both are equal then strcmp ( ) function returns zero.

Program to compare two strings in C.

#include <stdio.h>

#include <string.h>

int main()

{

char str1[]=”come”;

char str2[]=”Welcome”;

int w,x,y,z;

w = strcmp(str1, “come”);

x = strcmp(str1, “Welcome”);

y = strcmp(str1,”f”);

z = strcmp(str1,”feel”);

printf (“w=%d\n x=%d\n y=%d\n z=%d\n”, w,x,y,z);

return 0;}

Output:

strcpy() function in C

Strcpy( ): This function moves or copies the content of one string into another string.

Syntax

strcpy (string1, string2);

Program to copy the content of one string to another string in C.

#include <stdio.h>

#include <string.h>

int main()

{

char str1[] = “DIGITAL”;

char str2[] = “INDIA”;

strcpy(str1,str2);

printf(“Final String = %s\n”, str1);

return 0;

}

Output

Final string = INDIA

Note: If the length of the destination string is less than the source string then the source string is not copied into the destination string.

Strchr() Function in C

strchr ( ): This function helps you to find the first occurrence of the desired character in a string.

Syntax

strchr ( string, i);

Program to find the desired character in a string.

#include <stdio.h>

#include <string.h>

int main()

{

char str[]=”The C programming languages”;

char *ptr;

ptr = strchr (str,’m’);

printf (“String in which first character is occur = %s\n”, ptr);

return 0;

}

Output

String in which the first character is occurring =mming languages

Strrchr()function in C

Strrchr ( ): This function tells about the last occurrence of the desired character in a string.

Syntax

strrchr(Name_of_string, ‘Desired Character);

Program to find out the last occurrence of the desired character in a string.

#include <stdio.h>

#include <string.h>

int main()

{

char str[]=”The C programming language”;

char *ptr;

ptr = strrchr(str,’i’);

printf (“The Last occurence of character in a string = %s\n”, ptr);

return 0;

}

Output

The last occurrence of the character in a string = ing language

Strstr() function in C

Strstr ( ): With the help of this function we can find the desired string in the given string.

Syntax

strstr(Name_of_string, “desired string”);

C Program to find the desired string in given string.

#include <stdio.h>

#include <string.h>

int main()

{

char str[]=”the c programming language”;

char *ptr;

ptr = strstr (str, “programming”);

printf (“First occurrence of string is =%s\n”, ptr);

return 0;

}

Output

The first occurrence of the string is = programming language.

Strlwr() function in C

Strlwr ( ): This function converts a given string into lower case.

Syntax

strlwr (string);

C program to convert the string in to lower case.

#include <stdio.h>

#include <string.h>

int main()

{

char str[]=”MANGO SEASON IS BACK”;

printf(“%s\n”,strlwr(str));

return 0;

}

Output

mango season is back

strupr() function in C

Strupr ( ): This function converts the string into upper case.

Syntax

strupr (Name_of_string);

C program to convert a string into uppercase.

#include <stdio.h>

#include <string.h>

int main()

{

char str[]=”delhi”;

printf (“%s\n”,strupr(str));

return 0;

}

Output

DELHI

Strrev() function in C

Strrev( ): This function reverses the given string.

Syntax

strrev(Name_of_string);

C program reverse the given string.

#include <stdio.h>

#include <string.h>

int main()

{

char str[]=”Mumbai”;

printf(“%s\n”,strrev(str));

return 0;

}

Output

iabmuM

strtok() function in C

strtok ( ): This function breaks the string using a delimiter.

Syntax

strtok(Name_of_string);

C program in which a string is broken into substring.

#include <stdio.h>

#include <string.h>

int main()

{

char str[]=”Hello:World:Hello:Hi:Meet:them”;

char *ptr;

ptr=strtok(str,”:”);

while(ptr!=NULL)

{

printf (“%s\n”,ptr);

ptr=strtok(NULL, “:”);

}

return 0;

}

Output

Hello

World

Hello

Meet

them

Passing strings to function in C

Strings in C is also called the character of the array. Strings pass in a function is similar the way the array is passed.

#include <stdio.h>

//Declaration of print function

void print_string(char str[]);

int main()

{

char str[]=”string”;

print_string(str); //Calling print function

}

//Definition of print function

void print_string(char str[])

{

puts(str);

}

Output

string

Pointers and Character Strings in C

We understand the Pointers and strings with the help of a programming example.

Pointers in C

#include <stdio.h>

int main()

{

char *name=”Shona”;

int length=0;

char *ptr=name;

while (*ptr!=0)

{

ptr++;

length++;

}

printf (“\n length of the string = %d\n”,length);

return 0;

}

Output

length of the string = 5