To be able to code hacks, you would need a Microsoft programme called Visual C++
To be able to learn about this programme, you would need to read books which is provided in 'Crossfire Hack Source Code' section in .pdf format! The are some really useful threads in that section which will help you start coding or the basics of C++
There are also lot of sites about C++ which can easily be found by searching through Google! Videos are also available in youtube. All you have to do is look up...