Instructions

Explain what the below example is doing and how is it doing it$.$

SET $/$P M$=$Type $1,2,3,$ or $4$ then press ENTER:

IF $\%M\%==1$ GOTO CALC

IF $\%M\%==2$ GOTO NOTE

IF $\%$ M$\%==3$ GOTO BOTH

IF $\%$ M$\%==4$ GOTO EOF