Add Civilcrm member detail in third party tcexam
You can do this, but you need to be a programmer, or hire one.

CiviCRM is well suited to this, TCExam is not because it has no API.  If they both live on the same server, that's not too bad though.

Write an extension for CiviCRM that uses hook_civicrm_post.  When a completed contribution is added, make a connection to TCExam's SQL database and insert a new user record.

Instructions for writing an extension are available here and here.