In main function we declare required variable.
printf(" enter choice
1)encode
2)view ecoded file
3)
decode
4)view decoced file
5)exit ------");
// this is to print the main menu
scanf("%d",&ch); // entering
of choice
while(ch!=5) // until
choice is exit
{
if(ch==1) //if
choice is to encrypt
{
scanf("%s",name); // accept file
name
scanf("%c",&ff); //accept the
choice of change
// the file position or not
if(ff=='c'||ff=='C')
{strcpy(encri,ruf);scanf("%s",encri);} // so as to change enter file path
cscanf("%s",pass); // enter
password
l=strlen(pass); // l
=string length of password
st=fopen(name,"r"); // open the
file to be encrypted
ed=fopen(encri,"w"); // open the file
to where to be
//
encrypted
while(!feof(st)) // until end
of file to be encrypted
{ x=fgetc(st); // read each
character into X
fputc(x+pass[i++%l],ed); // write the sum of X
and password
} //
char
fclose(st); // close first
file
fclose(ed); // close second file
}
if(ch==3) // if choice is
decryption
{
scanf(“%sâ€,encri); //enter the file name
to be decrypted
ed=fopen(encri,"r"); //open the above mentioned
file
scanf("%c",&ff); //accept the choice of
change
// the file
position or not
if(ff=='c'||ff=='C')
{ strcpy(decri,ruf);
scanf("%s",decri); // so as to change enter file path
}
cscanf("%s",pass); // enter password
de=fopen(decri,"w"); //open a file to store decoded
data
while(!feof(ed)) // until end of file to be
encrypted
{
x=fgetc(ed); // read each character
into X
fputc(x-pass[i++%l],de); // write the sum of X and password
} // char
fclose(ed); // close first file
fclose(de); // close second file
}
if(ch==2) //if choice is to view the
contents encoded file
{
ed=fopen(encri,"r"); //open that file and read each
character
while(!feof(ed))
printf("%c",fgetc(ed)); //print them until end of file
fclose(ed); // close this file
}
if(ch==4) //if choice is to view the
contents decoded file
{
ed=fopen(decri,"r"); //open that file and read each
character
while(!feof(ed))
printf("%c",fgetc(ed)) ; //print them until end of file
fclose(ed) ; // close this file
}
scanf("%d",&ch); // enter the choice from menu
} // end while
} // end main