Computer Memory

                                                                   

Computer Memory

It is an internal storage area in the computer system. The term memory is used for physical memeory which refers to the actual chips capable of holding data. There is also a virtual memory, which expand physical memory on to a hard disk. There are two types of memory use in computer primary and secondary.

The term memory can be categorized in two ways…

Ø  Primary Memory:

Every computer comes with a certain amount of a physical memory, usually referred to as main memory for example (RAM and ROM).

Ø  Secondary Memory:

These types of memories are internal or external devices either inside or outside the computer.

It store programs and data permanently. It is slower, but cheaper. Floppy disks, hard drives, CD, DVD, pen Drive etc. are secondary storage devices. The secondary storage can be divided into Magnetic device, Optical Device and Flash Memory

v  RAM (Random Access Memory):

It is a temporary (volatile) storage area utilized by the CPU. Before a program runs, the program is loaded into the memory which allows the CPU direct access to the program.There are two types of RAM.

1.)SRAM (Static RAM): 
Abbreviation is Static Random Access Memory that is faster and more reliable than the more common DRAM (Dynamic RAM). The term static is derived from the fact that it does not need to be refreshed like Dynamic RAM. SRAM is often used only as a memory cache usually found in the CPU (L1, L2, and L3 cache)

2.)DRAM (Dynamic RAM): 
Stands for Dynamic Random Access Memory, type of memory used in most Personal Computer. There are some types of DRAM as following.

· SDRAM: 
It stands for Synchronous Dynamic Random Access Memory a new type of DRAM that can run at much higher clock speeds than conventional memory. SDRAM actually synchronizes itself with the CPU.

· DDR2-SDRAM: 
Abbreviation is Double Data Rate Synchronous DRAM2 is a type DDR that supports higher speed than it’s ancestor DDR SDRAM.

· DDR3-SDRAM:  
Abbreviation is Double Data Rate Synchronous DRAM3 is the newest type of DDR that supports the fastest speed of all the SDRAM memory.

v  ROM (Read Only Memory):

Computers always contain a small amount of Read-Only Memory that holds instructions for starting up the computer. Unlike RAM, Rom cannot be written to. It is non-volatile which means once you turn off the Computer the information is still here. BIOS (Basic Input Output System) is also the type of ROM. There are some types of ROM.

· PROM (Programmable Read Only Memory):

A PROM is a memory chip on which data can be written only one once. The different between a PROM and ROM is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process.

· EPROM (Erasable Programmable Read Only Memory):

It is a special type of PROM that can be erased by exposing it to ultraviolet light. Once it is erased, it can be programmed. An EEPROM is a similar to a PROM, but requires only electricity to be erased.

· EEPROM (Electrically Erasable Programmable Read Only Memory):

Pronounced double e-e-prom or e-e—prom, an EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast RAM. EEPROM is similar to flash memory (sometimes called flash EEPROM).