This is the question appeared in our sessional exam related to shell programming
What do you mean by $?,$#,$* and $$.
Can anyone help me to answer this question?
They are bash variables. Look for 'special parameters' here.
How can I write the answer in simple words?
They are "special parameters" available in all Bourne-type shells.
See the man page of your shell for more details.
Did you follow the link I provided? Did you look on the resulting page for the text I suggested? Some initiative on your part is expected.