Encryption and Decryption in C Programming

Hello all, I am planning to create well designed Encryption and Decryption Program in C (please also see the photos and samples that i added), but i dont know where should i start,
my first question is:
Can we reshape a text taken from the user based on which column in the table with the letters in the table? For example, would you please examine the picture below?

my sample run:Attachment 16061Attachment 16062

people who know about chipers and cryption, please help :)) thanks a lot.

That doesn't seem like a particularly useful question though since the answer is surely "yes", although it would be more common to say "convert" rather than "reshape".