String functions programs

       Program for comparison between two strings :-

       #include<stdio.h>
       #include<string.h>
       main()
       {    
               char a[100], b[100];   
               printf("Enter the first string\n");   
               gets(a);   
               printf("Enter the second string\n");   
               gets(b);   
               if( strcmp(a,b) == 0 )      
               printf("Entered strings are equal.\n");   
               else      
               printf("Entered strings are not equal.\n");   
               return 0;
         }

       Program for copy of two strings :-

       #include<stdio.h>
       #include<string.h>
       main()
       {
               char source[] = "C program";   
               char destination[50];   
               strcpy(destination, source);   
               printf("Source string: %s\n", source);   
               printf("Destination string: %s\n", destination);   
               return 0;
        }

       Program for String Reverse :-
       
       #include<stdio.h>
       #include<string.h>
       main()
       {   
               char arr[100];   
               printf("Enter a string to reverse\n");   
               gets(arr);   
               strrev(arr);   
               printf("Reverse of entered string is \n%s\n",arr);   
               return 0;
        }


        Program for Append the two Strings :-

        #include<stdio.h>
        #include<conio.h>
        #include<string.h>
        main()
        {   
               char a[100], b[100];   
               printf("Enter the first string\n");   
               gets(a);   
               printf("Enter the second string\n");   
               gets(b);   
               strcat(a,b);
               printf("String obtained on concatenation is %s\n",a);   
               getch();   
               return 0;
         }

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string functions

     
        
Strings are used in string handling operations such as,

• Counting the length of a string.
• Comparing two strings.
• Copying one string to another.
• Converting lower case string to upper case.
• Converting upper case string to lower case.
• Joining two strings.
• Reversing string.

STRINGS STANDARD FUNCTION:-
----------------------------------------------
strlen():-determines length of a string.

strcpy():-copy a string from source 2 destination.

strncpy():-copy achars of a string 2 another string up 2 specified length.

strcmp():-compares 2 strings(depends on b/w small & capital).

stricmp():-compares 2 strings(doesn't depends upon b/w small & capital).

strncmp():-compares 2 strings of specified lengtgh.

strnicmp():-compares 2 strings(doesn't depends upon b/w small & capital)of specified lengtgh.

strlwr():-converts uppercase string 2 lowercase string.

strupr():-converts lowercase string 2 uppercase string.

strdup():-duplicate a string.

strchr():-determines 1st occurance of a given char in a string.

strrchr():-determines lost occurance of a given char in a string.

strstr():-determines 1st occurance of a given string in another string.

strcat():-appends source string 2 destination string.

strncat():-appends source string 2 destination string upto specified length.

strrev():-reverse all charecters of astring.

strset():-sets all chars of astring with a given argument or symbol.

strnset():-sets all chars of astring with a given argument or symbol upto specified length.

strspn():-finds upto what length two strings are identical.

 

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string examples

#include<string.h>
main()
{
     char arr1[9]={'w','e','l','','c','o','m','e'};
     char arr2[9]="welcome";
     char arr3[9]={{'w'},{'e'},{'l'},{''},{'c'},{'o'},{'m'},{'e'}};
     clrscr();
     pf("\narray1=%s",arr1);
     pf("\narray2=%s",arr2);
     pf("\narray3=%s",arr3);
}
 
output :-
                array1= wel come
                array2= welcome
                array3= wel come

example for counting elements :-
   
#include<string.h>
main()
{
    char text[17]="RANDOM ACCESS";
    clrscr();
    printf("%s\n",text);
    printf("%.5s\n",text);
    printf("%.8s\n",text);
    printf("%.15s\n",text);
    printf("%17s\n",text);
    printf("%-10.4s\n",text);
    getch();
}

output :-

RANDOM ACCESS
RANDO
RANDOM A
RANDOM ACCESS
RANDOM ACCESS
RANDOM ACC

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strings in c-language

                                              STRINGS
 
    
String :-

A string is a collection of characters. Strings are always enlosed in double quotes as "string_constant".
 

In C language Strings are defined as an array of characters or a pointer to a portion of memory containing ASCII characters. A string in C is a sequence of zero or more characters followed by a NULL '\0' character:

It is important to preserve the NULL terminating character as it is how C defines and manages variable length strings. All the C standard library functions require this for successful operation.

All the string handling functions are prototyped in: string.h or stdio.h standard header file. So while using any string related function, don't forget to include either stdio.h or string.h. May be your compiler differs so please check before going ahead.

If you were to have an array of characters WITHOUT the null character as the last element, you'd have an ordinary character array, rather than a string constant.

String constants have double quote marks around them, and can be assigned to char pointers as shown below. Alternatively, you can assign a string constant to a char array - either with no size specified, or you can specify a size, but don't forget to leave a space for the null character!

Declaration of Strings :-

     datatype variable name array length=value;

example :-  datatype is char, converted into string by using the
                   systemcode "%s",

                   char  a[10]={"hello"};
                                (or)
                   char a[10]={'h','e','l','l','o'};
                                (or)
                   char a[10]={{'h'},{'e'},{'l'},{'l'},{'o'}};
                
                   in strings space( ) , .  is also counted.


 

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check addresses are correct or not

    /* cosider 3 variables and find the addresses ,first two variables
        addresses difference is equal to another two variables  
        addresses  difference. */

#include<stdio.h>
main()
{
int x=10,y=20,z=30;
clrscr();
printf("address of x=%d\n",&x);
printf("value of x=%d\n",x);
printf("address of y=%d\n",&y);
printf("value of y=%d\n",y);
printf("address of z=%d\n",&z);
printf("value of z=%d\n",z);
getch();
}

output :-
address of x= -12
value of x= 10
address of y= -14                       
value of y= 20
address of z= -16
value of z= 30

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pointer examples

 

   

1)   Meaning of following simple pointer declaration and definition:

 

int a=5;

int * ptr;

ptr=&a;

Explanation:

About variable a:

1. Name of variable: a

2. Value of variable which it keeps: 5

3. Address where it has stored in memory: 1025 (assume)

About variable ptr:

4. Name of variable: ptr

5. Value of variable which it keeps: 1025

6. Address where it has stored in memory: 5000 (assume)

Pictorial representation:

 

 

 

 

 

Note: A variable where it will be stored in memory is decided by operating system. We cannot guess at which location a particular variable will be stored in memory.

(2) Meaning of following pointer declaration and definition:

int a=50;

int *ptr1;

int **ptr2;

ptr1=&a;

ptr2=&pt1;

 

Explanation:

About variable a:

1. Name of variable: a

2. Value of variable which it keeps: 50

3. Address where it has stored in memory: 5000 (assume)

About variable ptr1:

4. Name of variable: ptr1

5. Value of variable which it keeps: 5000

6. Address where it has stored in memory: 9000 (assume)

About variable ptr2:

7. Name of variable: ptr2

8. Value of variable which it keeps: 9000

9. Address where it has stored in memory: 9555 (assume)

Pictorial representation of above pointer declaration and definition:

 

 

Note:

 

‘*‘is known as indirection operator which gives content of any variable.

& is known as reference operator which gives address where variable has stored in memory.

 

Cancellation rule of above two operators:

 

* and & operators always cancel to each other i.e.

*&p=p

But it is not right to write:

&*p=p

Simple example:

 

What will be output of following c program?

#include<stdio.h>

int main(){

int x=25;

int *ptr=&x; //statement one

int **temp=&ptr; //statement two

printf(“%d %d %d”.x.*ptr,**temp);
return 0;

}

 

Output: 25 25 25

Explanation:

As we know value of variable x is 25.

 

*ptr= *(&x) //from statement one

=*&x

=x //using cancellation rule

=25

**temp= **(&ptr)=*(*&ptr)=*ptr=*(&x)=*&x=x=25

Example :-

#include<stdio.h>

main()

{

int x=10,*ptr;

clrscr();

ptr = &x;//(address of the variable)

*ptr = x;//(value of the variable)

printf("address of x=%d\n",ptr);

(or)

printf("address of x=%d\n",&x);

printf("value of x=%d\n",*ptr);

(or)

printf("value of x=%d\n",x);

getch();

}

output :-

address of x= -12

address of x= -12

value of x= 10

value of x= 10

 

 

  

   

          

     

  

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