I’m sitting at my brother’s house, watching TV. Then my 3-year-old nephew runs u

I’m sitting at my brother’s house, watching TV. Then my 3-year-old nephew runs up to me:
– Uncle Borya, who is a programmer?
– Better ask your mom, she’ll tell you better. The nephew, satisfied, runs into the kitchen and returns after a while: “Mom said that you will explain to me who a programmer and a switchman are.”