Introduction to Read Only Memory (ROM)
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Introduction to Read Only Memory (ROM)

Read Only Memory (ROM) is simple type of memory, whose contents cannot be change even after loss of electrical power. Read Only Memory (ROM) chip contain fixed start up instructions. It cannot be written or erased by the computer user, only trained programmers can write by using special equipments.

As we know in computer terminology read means transferring data instruction from an input source to the computers main memory (or CPU) and write is transferring data/instructions from computers main memory to an output device. Therefore, Read only means data/instruction can be retrieved from the ROM Chip but cannot be modified. Read Only Memory (ROM) is simple type of memory, whose contents cannot be change even after loss of electrical power. Read Only Memory (ROM) chip contain fixed start up instructions. It cannot be written or erased by the computer user, only trained programmers can write by using special equipments. There are two types of read only memory, namely, (a) manufacturer programmed, and (b) user-programmed.

(a) Manufacturer Programmed ROM : ROM is one in which the contents are programmed by the manufacturer during the construction of the chip, it is unalterable. Usually, ROM are used for high volume controlled applications such as the set of instructions that is needed to make the computer system ready for use when its power is switched on, known as “system boot program”. These instructions are start up instructions, commonly found in ROM. ROM-BIOS means Read Only Memory Basic Input Output Services. These services or instructions perform the basic control over the hardware including I/O devices. Generally, ROM chip of a computer stores Operating System, Disk Drive, Printer Drivers, etc. Thus, ROM stores program and data which do not change and are frequently used.

(b)User-Programmed ROM : The user-programmed ROM is one in which user can load and store read only programs and data. The user-programmed ROM include the following :

Programmable Read Only Memory (PROM): it can be written once via an irreversible process. PROM is a non-volatile storage, i.e. the stored information cannot be changed even if the power is switched off.

Erasable Programmable Read Only Memory (E PROM): Data on E PROM can be erased to store new information. However, the information on this chip can only be read. When the E PROM is in use, information in the chip remains until it is erased. E PROM chips are generally used by R&D personnel who test the efficiency of the system with new programs. E PROM is of two types namely, Electrically Erasable Programmable Read Only Memory (E PROM) and Ultra Violet Erasable Programmable Memory .

Flash Memory : Flash memory is small variant of Electrically Erasable Programmable Read Only Memory. These memory chips are the latest known storage devices, available in capacities ranging from 1 MB to 512 MB. They are non-volatile memories as they retain the data stored in them without a power source.

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Comments (1)

Thanks for making ROM so easy to understand. I need all the help I can get! :)

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