ROM AND ITS TYPES
ROM stands for Read Only Memory. It
is type of internal memory. The data and instructions in ROM are stored by the
manufacturer at the time of its manufacturing. This data and programs cannot be
changed or deleted after wards. The data or instructions stored in ROM can only
be read but new data or instructions cannot be written into it. This is the
reason why it is called Read Only Memory.
ROM stores data and instructions permanently. When the power is turned off, the instructions stored in ROM are not lost. That is the reason ROM is called non-volatile memory.
ROM is used to store frequently used instructions and data to control the basic input & output operations of the computer. Mostly, frequently used small programs like operating system routines and data, are stored into the ROM. When the computer is switched on, instructions in the ROM are automatically activated. These instructions help the booting process of computer.
ROM stores data and instructions permanently. When the power is turned off, the instructions stored in ROM are not lost. That is the reason ROM is called non-volatile memory.
ROM is used to store frequently used instructions and data to control the basic input & output operations of the computer. Mostly, frequently used small programs like operating system routines and data, are stored into the ROM. When the computer is switched on, instructions in the ROM are automatically activated. These instructions help the booting process of computer.
Types of ROM
ROM is divided into following types:
1.
PROM
2.
EPROM
3.
EEPROM
1- PROM
PROM stands for Programmable Read Only Memory. This form of ROM is initially blank. The user or manufacturer can write data/program on it by using special devices. However, once the program or data is written in PROM chip, it cannot be changed. If there is an error in writing instructions or data in PROM, the error cannot be erased. PROM chip becomes unusable.
PROM stands for Programmable Read Only Memory. This form of ROM is initially blank. The user or manufacturer can write data/program on it by using special devices. However, once the program or data is written in PROM chip, it cannot be changed. If there is an error in writing instructions or data in PROM, the error cannot be erased. PROM chip becomes unusable.
2- EPROM
EPROM stands for Erasable Programmable Read Only Memory. This form of ROM is also initially blank. The user or manufacturer can write program or data on it by using special devices. Unlike PROM, the data written in EPROM chip can be erased by using special devices and ultraviolet rays. So program or data written in EPROM chip can be changed and new data can also be added. When EPROM is in use, its contents can only be read.
3- EEPROM
EEPROM stands for Electrically Erasable Programmable Read Only Memory. This kind of ROM can be written or changed with the help of electrical devices. So data stored in this type of ROM chip can be easily modified.
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