What Is Read Only Memory And Light Pen ?

Read only Memory:
The name gives the idea, we can only read this memory, we can not write in this memory. This basically contains messages and instructions from the manufacturer. Like how to start computer, check every part of it s memory. When the machine is turned on, it works under the control of ROM, which performs the below mentioned important functions:

a. Displays messages from manufacturer.
b. Runs the power-on-self-test- (POST), which checks the memory, keyboard, drives, printers and all attached equipment.
c. Searches for an operating system. If it finds an operating system the control would be transferred to that operating system is supplied, then the ROM will hang the machine and we will not be able to work.

d. Loads the basic input output system (BIOS) which works with the microprocessor for controlling the inputs and outputs. That is why sometimes, ROM is known as ROM BIOS.
This part is unchangeable and non-volatile. Several types of ROMs are available like PROM, EPROM, EEPROM.
Light pen:
In touch screen in put can be given by touching the specialized screen. But to use this touch capability in on a simple screen, the solution is the light pen- an input device that can make selections, place objects or indicate dimensions by simply touching the screen.