Hi guys. . I'm a newbie /maybe dummy / teacher gave me homework.. but I can"n solve it.. Can sum1 help me?? Write a C program that will input a 9-digit Credit Card Number, and will check whether iit is valid or not (i.e. to examine if the last 2 digits of the Credit Card Number can be generated from the first 7-digit number) I've started this thread appealing to lead.smart34's advice.. All "responsibilities" belongs to her/him.. Now let present my sollution. algortihm : 1- enter 9 digited numbers 2- get 3rd 4 and 5th digits and create a 3 digited number. say this number x 3- find square of x 4- get 8 and 9 th digits and say this 2 digited number y 5- compare x and y in (mod10) 6.a- if they're equal in mod10 print "valid credti card number" 6.b- else "invalid credit card number" Firstly I defined the a1, a2 ... a9 variables. Then wrote the printf("Enter 9 digited c.c. numba" ); then, scanf all a1 a2 ... a9 I dont know how to get a3a4a5 and a8a9 as a number. I can do the end.. Such let's say x to the square of a3a4a5.. and y to a8a9 /two digited number/ Then we can compare . if(x %10== y) { printf("valid c.c. number"); } else { printf("invalid c.c. number"); } I hope I could describe the problem..

helo macchiato, I ll giv u a code which i think can b useful 2 convert frm individual digits 2 a no.supose u hav 3 diferent no.a[3],a[4],a[5].u can combin dem by s=100*a[3]+10*a[4]+a[5] similarly p=10*a[8]+a[9]

helo macchiato, I ll giv u a code which i think can b useful 2 convert frm individual digits 2 a no.supose u hav 3 diferent no.a[3],a[4],a[5].u can combin dem by s=100*a[3]+10*a[4]+a[5] similarly p=10*a[8]+a[9].i hope u ca do d rest