a promenade concert
"The engineer decided to use a programmable read-only memory chip to store the fixed boot sequence for the new microcontroller."
Programmable read-only memory: A PROM chip can be programmed one or more times (depending on the type) and generally cannot be re-programmed without special equipment. Once programmed and installed in a device, it functions as a read-only chip (as if it had been hard-wired to function that way.)
In plain English: A prom is a formal dance that high school students attend to celebrate their graduation year with friends and dates.
"She spent all her extra money on a new dress for prom."
A surname.
"Mr. Prom is my next-door neighbor who loves gardening."
The word "prom" is a shortened form of the French word promenade, which originally meant a walk or stroll. It entered English usage to refer specifically to a formal dance attended by high school students.