When you program a programmable calculator like the HP65 you press buttons and it remembers the steps you are telling it. Then when you run the program, it re-does those button presses again to calculate the result. Every time you run the program it does those steps. This happens even though you only entered them once. That’s the point.

Internally, the calculator stores a program code for each key press or combination of key presses. With the HP65 it is mostly “one key press, one stored code” but there are a few combinations it recognises and saves as one program code. These are called “merged program steps”.
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