ROM: Read-Only Memory

ROM (Read-Only Memory)

ROM (read-only memory) is nonvolatile memory, generally installed by the vendor of the computer during the process of manufacturing the motherboard or secondary components that need to retain code when the machine is turned off. ROM is used extensively to program operation of computers, as well as in devices like cameras, and controls for the fuel injectors in modern cars. However, ROM plays a limited role in the PC. Here, it holds the instructions for performing the POST routine and the BIOS information used to describe the system configuration.

Secondary Storage Devices

Secondary Storage Devices:-

Secondary storage devices are used to store data Permanently. The data on secondary storage devices can be shifted from one computer to another computer easily.
It has three types.
Magnetic Disk
Magnetic Tape
Optical Disks

Magnetic Disk

            It is most widely used storage media for all type of computer. A magnetic disk is a thin circular metal plate or platter coated with magnetic material. Information can be record on or read from the magnetic surface through magnetism. Magnetic disk is a random access storage media.

Types of Magnetic Disk
There are the following types of the magnetic disk

1. Hard Disk 
2. Floppy Disk 
3. Zip Disk 
4. USB flash Drive

Magnetic Tape (Sequential Access)

It is an example of old type storage media to store large amount of data permanently. Magnetic Tape consists of a thin ribbon of plastic. The tap is coated with magnetic material. The process of reading or writing of data on the tape is very slow. In magnetic tape, data can only be accessed sequentially. It is mostly used for taking backup of data.

Optical Disks

Optical disk issued laser technology to read or write information. LASER Stands for Light Amplification through stimulated emission of Radiation Laser beam is used to make tiny holes on the surface of the disk. 

Compact Disk (CD)

CD is the most popular optical medium. It can hold 650 MB to 800 MB of data. The data on the CD cannot be erased like magnetic diskettes. 

DVD

DVD, also known as "Digital Versatile Disc" or "Digital Video Disc", is an optical disc storage media format. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs (CDs), but store more than six times as much data

Read Only Memory (ROM)

Read Only Memory (ROM):-

ROM stands for Read only Memory. It consists of those instructions that prepare the computer for use. ROM instructions are automatically loaded into the Main Memory. These instructions cab only be read but cannot be changed or deleted. It is not possible to write new instructions into the ROM. It stores data and instructions permanently. When we switch off the computer, the instructions stored in the ROM are not lost. Therefore it is called a non-volatile memory. 

Primary Storage or Main Memory (RAM)

Primary Storage or Main Memory (RAM) :-

Primary storage, presently known as main memory or simply RAM (Random Access Memory), is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner.

Memory stores three basic categories of data.

1. Operating system and other system software that control or maintain the computer and its devices
2. Application programs that carry out a specific task such as word processing etc.
3. Data to be processed by the application programs and resulting information.

 RAM varies in size like 128 MB, 256 MB, 512 MB to 4 GB.  RAM can not store data and instruction permanently. When we switch off the computer, all data and instructions from RAM are washed or vanished. Therefore it is called volatile memory.