Subject: Computer Basics
Based on their read write capability and their storage capability, computer memory can be one the following types.
ROM is the computer memory on which data is prerecorded. Once data has been written onto a ROM chip, it cannot be removed and can only be read. Unlike main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile. For e.g., ROM- BIOS (Basic Input and Output System). The function of BIOS is to load files from CD or Hard Disk into primary memory (ROM).
Here data and instruction are programmed during manufacturing process and if it malfunctions we have to replace it with new one, e.g. ROM- BIOS
Programmable read-only memory (PROM) is read-only memory ( ROM ) that can be modified once by a user. PROM is a way of allowing a user to tailor a microcode program using a special machine called a PROM programmer .
EPROM is reprogrammable ROM. We can erase the content written in EPROM and replace it with new one. The programs are erased using UV rays.
EEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., device configuration.
Like EEPROM, flash memory can be erased by electrical signal and erasing process is faster than EEPROM. It is possible to erase a particular block of data or instructions instead of entire data bits in flash memory.
It stores information in the form of charge; there is probability of leakage of charge, so it needs to be regularly refreshed. It can store more information than static RAM (S-RAM). Capacitor is the device that's used to store the charge, e.g. DDR, DDR2
Unlike D- RAM, S- RAM stores information in the form of voltage. It is much faster than D-RAM and it is fully able to keep pace with modern processor. Here transistors are used instead of capacitor so refreshing is not required . The S-RAM chips are physically larger but stores less bits per area.
|i. It stands for Read only memory||i. It stands for Random Access memory.|
|ii. It is non-volatile (permanent) memory.||ii. It is volatile (temporary) memory.|
|iii. It's types are PROM, EPROM, EEPROM etc.||iii. It's types are SRAM, DRAM etc.|
|i. It stands for static Random Access
|i. It stands for dynamic Random Access
|ii. It does not need periodic
|ii. It needs periodic refreshing.|
|iii. It stores data in the Flip-Flop
|iii. It stores data in transistor state.|
The functions of RAM are:
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