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.

How can I write the answer in simple words?

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.

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