I need a simple C program ASAP

Hello all, I used to program in C++ but I need a program in C and I kind of forgot a lot of the stuff from C++ and I don't handle C too well. I need a program where I need to enter an N number of patients. Each patient's details must be written to the file and encrypted using this algorithm: wrapping around from 'z' to 'a' and '9' to 'a'. Punctuation and spaces remain unencrypted. The name for each file will be the patient's last name, plus their date of birth as 6 digits with an extension of ".aow" example : "[login to view URL]". The data written to the file should be the patient's: Full name, date of birth, height, waist measurement, weight and a comment. Thank you a lot for viewing this post and thank you in advance!