What does "punch in" mean?

Also, punch a or the clock. Check in at a job upon arrival, as in You have to punch in or you won't get paid, or In this office no one has to punch a clock. This usage alludes to the use of a time clock, which has a button an employee punches or strikes to record the time of arrival on a card. [1920s] Also see punch out, def. 1.

Keyboard data into a computer, as in He was careful about punching in all the payments. [Mid-1900s]