Program To Accept A Line Of Text Into A String Array And Then Encrypt The Contents Of The Array

/*  Program To Accept A Line Of Text Into A String Array And Then
		  Encrypt The Contents Of The Array As Given Below
		    Encryption
		    __________

a -> b    |    A -> B       |     0 ->1
		     b -> c    |    B -> C       |     1 -> 2
		     c -> d    |    C -> D       |     2 -> 3
		       |       |        |        |        |
		       |       |        |        |        |
		     z -> a    |      Z -> A     |      9 -> 0
		       DISPLAY THE TEXT AFTER ENCRYPTION AND THEN DECRYPT
			   THE CONTENTS OF THE ARRAY AS GIVEN BELOW

DECRYPTION
		     ___________

a <- b   |    A <- B     |    0 <- 1
		     b <- c   |    B <- C     |    1 <- 2
			|     |      |        |       |
			|     |      |        |       |
		     z <- a   |    Z <- A     |    9 <- 0
			 DISPLAY THE TXET AFTER DECRYPTION             */

#include<stdio.h>
#include<conio.h>
void main()
{	char text[100];
	int i;
	clrscr();
	printf("\n enter a line of text(EOF to stop..) \n");
	gets(text);
	for( i=0;text[i]!='\0';i++ )
	{  if( isalpha (text[i]) )
	     {  if( text[i]=='z' )
		   text[i]='a';
	       else if ( text[i]=='Z' )
		   text[i]='A';
	       else
		   text[i]=text[i]+1;
	     }
	    else if(  text[i])
	     {  if( text[i]=='9' )
		    text[i]='\0';
		else
		    text[i]=text[i]+1;
	     }
	printf("\n after encrytion \n %s",text);
	for( i=0;text[i]!='\0';i++ )
	 { if( isalpha(text[i]) )
	   {  if ( text[i]=='a' )
	       text[i]='z';
	      else if( text[i]=='A' )
	       text[i]='Z';
	      else
	       text[i]=text[i]-1;
	   }
	  else if( isdigit( text[i]) )
	   {  if( text[i]=='\0' )
		  text[i]='9';
	      else
		 text[i]=text[i]-1;
	   }
	 }
	printf("\n after decrytion \n %s",text);
	getch();
}

Please send comments to vgdarur.javafive@blogger.com