Yes, you are eligible to apply for the Indian Air Force after B.Tech in Computer Science; you can apply for the Aeronautical Engineers Course in both Electronics and Mechanical branch in the Indian Air Force. Following are the details of it:

Eligibility:
The applicant should hold Degree in Engineering in Electronics/Telecom/Electrical/Electronics and Communication/Instrumentation/Computer Science branch from recognized institute

Age limit:
You should be minimum 17 and max age is 25

You need to appear in the entrance examination which covers following topics:

Mathematics
History
Aptitude
Geography
General Knowledge
Current Affairs