ROM memory features: What is ROM and how it works

The ROM memory of a computer has the main characteristics of being non-erasable, non-rewritable and is less expensive than RAM as it is made with much simpler circuits.
The abbreviation ROM means Read Only Memory or read-only memory and, unlike RAM, maintains the information even in the event of a power failure, for this reason it is defined as non-volatile as opposed to the RAM which is volatile instead (it loses data at the moment in which there is no electricity).

The ROM memory contains information for booting the PC. Every time the computer is turned on, the processor checks the type of hardware that is present, and, through various control tests, that there are no problems for any component. This information is written in the ROM memory circuits by the computer manufacturer.
The ROM memory is smaller than the RAM, precisely because it must contain little software, the few instructions to start the PC. A software of this type, implemented by the PC manufacturer directly on the circuits, a software written in the hardware, a hybrid, takes the name of firmware.
In particular the ROM firmware is called BIOS which means Basic Input Output System, that is the basic operations that a PC performs at startup.

The start operation is called bootstrap (and therefore initial start-up) which is divided into three phases:

1. hardware verification,
2. hardware activation,
3. start the basic computer software, the operating system that we will see when we talk about the software.

Intuitively without the ROM memory the computer would not be able to turn on.