It is not clear what do you mean by an IIT INSTITUTE. Do you mean Indian Institute of Technology? Indian Institute of Technologies do not offer any correspondence course in Computer Science. If your objective is to do a post graduate course in computer, then in our opinion, you should do an M. Tech/ M. E in Computer Science and Engineering. Almost all the engineering institutions offering post graduate courses in Engineering, offer M. Tech / M. E in Computer Science and Engineering. For getting admission in an M. Tech / M. E course, you will have to qualify in GATE (Graduate Aptitude Test in Engineering). GATE is a competitive examination conducted by Indian Institute of Technology in the month of February every year. GATE is a single paper examination of 3 hours duration and generally consists of two sections. Section A is an objective type test, which is of 75 marks and Section B is a problem type test, which is of 75 marks. One can select an Engineering or Science subject from a list of subjects for appearing in the examination. As you want to do a post graduate course in Computer, you should select Computer Science as your subject.