In which memory,
processor can communicate directly is called primary memory. This memory stores
data or information temporarily. After processing data are stored into
secondary memory. There are different types of primary memory such as-
- ROM
- RAM
- Cache Memory.
ROM: Read only memory is shortly called ROM. The data stored in a ROM chip can only be read and used,
they cannot be changed. This is why it is called read only memory. At the time
of making ROM chip by the manufacturing company which data are stored, cannot
be deleted, stored permanently. But now a day's data of some ROM chips can be
changed or altered in some special ways.
Various types of ROM
chips are described below.
Mask ROM: In which
manufacture company, made ROM-Chip, they (that company) also write program own
and delivered in the market. Later this program can never be changed.
PROM (Programmable Read
Only Memory): In this case one manufacturing company makes only ROM chip and
another company writes program. This chip is also unchangeable.
EPROM (Erasable
Programmable Read Only Memory) : EPROM has a glass window, which covered with a
label. Program can be changed by high-intensity ultra violet ray with the help
of this glass window. Bright sunlight can cares EPROM. But no problem is raised
in room-light.
EEPROM (Electricity
Erasable Programmable Read Only Memory): EEPROM is more access able than
EEPROM. This ROM can be changed or updated bit by bit through electricity,
software or utility. At present EEPROM is used in PC as BIOS, which is
introduced as Flash BIOS.
RAM: RAM is an important
component of a computer. Acronym of RAM is Random Access Memory, which stores
data program temporarily while computer os started on. This is why it is called
temporary memory. While PC is started on, which works have been done by user,
are stored by RAM. In any time from any place of it, we can read or write data,
this is why it is called Random Access Memory. It is temporary because when
electricity is gone, all the data of it is deleted. So this memory is also
works or playing games minimum 128-256 MB RAM is needed. At present market
different branded RAM of different capacity are available such as 128 MB,
256MB, and 512MB etc. Recently South Korean Samsung Electronics has improved of
1GB DRAM which is proposed to deliver in market in this current year.
Mainly RAM has two
categories-
(a)
DRAM
(b)
SRAM
(a)
DRAM (Dynamic RAM): This type of RAM stores
charges into mini capacitor and saves data refreshing through external circuit.
(b)
SRAM (Static RAM): Static RAM can keep data in
keeping with power supply. Its speed is comparatively higher and it is more
expensive to make because flip-flop circuit makes it, which is expensive.
Generally this RAM is for cache memory.
- EDO RAM: When freely data writing is finished, this RAM can send data quickly. Having higher frequency EDO RAM is speeder than DRAM. This type of RAM is generally used for Pentium machine.
- SDRAM: This RAM is fit for Pentium-II and Pentium-III class computers. Its operating speed is 100 and 133 MHz.
- SGRAM: This RAM is suitable for using graphics card. At the time of working by taking information in video frame buffer, this RAM can swiftly read and write data for graphics processors.
- VRAM: This type of RAM is good for video card. Its every memory cell is of dual port.
- RDRAM: RDRAM is the fittest for high speed system like copper mine of Intel and Athlon of AMD. Its speed is 800 MHz and data transfer rate is 1.6 GB/Sec.
- CMOS RAM: CMOS RAM is a special type of RAM, which stored the configuration information of BIOS. CMOS RAM needs low power to CMOS RAM.
- Cache Memory: In which cache memory placed between the main memory and the microprocessor is called the external cache. The cache which built-in with the processor is called the internal cache. Cache memory is ten times speedy than main memory. It saves the access time and increase the speed and real performance of processor. Cache memory is very expensive to manufacture.
Secondary Memory or
Auxiliary Memory: In which memory processor cannot communicate directly is
called secondary memory. In this memory data are stored permanently. As
secondary memory Floppy disk, compact disk, Magnetic tape etc. are used.
