Strings in C language

             Strings in C 

 

Definition : It is a collection of characters. Character arrays are used to handle strings.

 

Declaration:

                        char  string_name[length+1];

 

Note: Here the purpose of  +1 is null character ( \0 ) to be maintained at end of the string. It indicates end of the string.

Any string operation performed up to null char ( \0 ), which is end of the string .

To accommodate null char one extra byte required.

 

Eg:

            char  str[10]   à it allows only 9 chars.

 

Memory Map of a String:

 

  str[0]         str[1]         str[2]       str[3]       str[4]        str[5]         str[6]      str[7]      str[8]        str[9]

 

Some String Operations are as follows: 

1. Reading of a String

2. Displaying and writing of  string

3. Length of a String

4. Copying strings

5. Comparison of strings

6. Concatenation of string

7. Reverse of a string.

1. Reading of a String:  

    Assignment: char str[10];

 

    str[0]        str[1]      str[2]          str[3]      str[4]      str[5]         str[6]      str[7]       str[8]          str[9]

H

E

L

L

O

\0

 

 

str[0]=’H’;

 str[1]=’E’;

str[2]=’L’;

 str[3]=’L’;

str[4]=’O’;

str[5]=’\0’;

 

str=”hello” ; à invalid

 

Multiple characters cannot be assign to strings.

 

In this scenario better to use strcpy()  function.

Eg:

            strcpy(str,”HELLO”);

 

Initialization:

 

char str[10]=”hello”;

char str[]=”hello”;

char str[6]=”hello”;

char str[5]=”hello”; à invalid, since one extra byte required to accommodate null char ( ‘\0’) into string.

This statement compile but it raises memory exception at run time.

 

Reading a string from key board:

 

scanf(“%s”,str);  à to read strings  & is not require since, string name itself is an address of the sting.

 

Eg :

input :

hello world   à scanf can read upto only space or tab or new line character ( enter key ).

                        Here value of str is “hello”

Displaying string:

 

            printf(“%s”,str);

 

Program to read and display a string.

 

 

#include<stdio.h>

#include<conio.h>

main()

{

char str1[30],str2[30];

            printf("\n Enter two strings");

            scanf("%s %s",str1,str2);

            printf("%s  %s",str1,str2);

getch();

}

 

Another way of reading a line is by using gets()  à is function to read a line.

 

gets(str) à  it will read input data up to enter key. It will read data including \n, but will not store into string.

 

If input data is more than the size of the string, then data overflow, hence it raises memory exception. So It is not recommended  to use .

 

And its alternative is : fgets() à is an alternative to gets() in  reading a line.

 

char str[10];

int n;

n =sizeof(str);

fgets(str,n,stdin);

 

This function will read input data up to enter key or ( n-1) chars, which ever comes first.

 

puts()à to display the string.

char str[10]=”hello”;

puts(str); (or)  puts(“hello”);  (or)  puts(“\n hello \n world”):

 

fputs()  à also to display the string.

Eg:

fputs(str, stdout);

 

this function is to insert \n at the data and write to output buffer. Hence cursor moves to next line.

 

 

Input function	Output function
scanf()	printf()
getchar()	putchar()
gets()	puts()
fgets()	fputs()

  

Program to display following out put as follows: 

            h

he

            hel

            hell

hello

 

        #include<stdio.h>

        main()

    {

          char str[50];

          int n,d;

          printf("\nEnter string1");

          scanf("%s",str);

          n=strlen(str);

          for(d=1;d<=n;d++)

          {

               printf("\n%*.*s",n,d,str);

           }

      getch();

    }

 

 

Note: All the programs given here are the solved programs and the compiler is also provided here for the user or viewer reference