Different behavior between g* and *

Hi, I noticed there is difference between '*' and 'g*', especially when modes are involved. For example, in c-mode when I hit '*' above some variable like 'sample_variable', only 'sample' gets highlighted and searched. However, with 'g*' 'sample_variable' is correctly highlighted.Similar behavior is in lisp-like modes and cases like 'sample-variable'. Is this expected behavior? Just checked vim behavior, and in both cases full variable name is highlighted and searched. Thanks, Sanel