The code used to boot up a computer is stored in:

Concept

A computer can begin executing only from storage whose contents are available immediately after power-on.

Boot firmware is therefore kept in non-volatile memory; volatile memories acquire useful contents only after startup begins.

Application

At reset, the processor fetches the firmware that initializes hardware and starts the boot sequence. Among the given choices, ROM is the non-volatile storage designed to retain that firmware when power is removed.

Contrast

• RAM is volatile working memory used after the machine has powered on.

• Cache is volatile high-speed memory that holds copies of recently accessed data and instructions.

• ROM retains firmware across power cycles and is readable as soon as the processor resets.

• CPU registers hold current operands and control state only while the processor is powered.

Result

Therefore, the boot-up code is stored in ROM.