hello sreenidhi, the staff selection exam comprises exams in tiers,

Tier I and Tier II exams are conducted in the online mode. 

Appearing for Tier I and Tier II exams is mandatory for all the posts. 

Tier III is a descriptive test to be conducted in pen and paper mode.

And there are certain posts that have the necessity to write TIER 4.

beat of luck.

SSC have both online and offline based tests. While Tier 1, 2 and 4 areonline computer based exam, Tier 3 is descriptive written pen and paper examination.