Computer Memory and it types RAM ROM AND CACHE MEMORIES

Computer Memory

1. Computer Memory
U.R Weerasinghe
EP/12/8776

2. INTRODUCTION
A memory is just like a human brain in human.
It is used to store data and instructions.
Computer memory is the storage space in computer where data is to
be processed and instructions required for processing are stored.
The memory is divided into large number of small parts called cells.
Each location or cell has a unique address which varies from zero to
memory size minus one.

3. Memory is can be divided into three types
Cache Memory
Primary Memory/Main Memory
Secondary Memory

4. CACHE MEMORY
Cache Memory Cache memory is a very high speed semiconductor
memory which can speed up CPU.
It acts as a buffer between the CPU and main memory.
It is used to hold those parts of data and program which are most
frequently used by CPU.
The parts of data and programs are transferred from disk to cache
memory by operating system, from where CPU can access them.

5. ADVANTAGES OF CACHE MEMORY
Cache memory is faster than main memory.
It consumes less access time as compared to main memory.
It stores the program that can be executed within a short period of
time.
It stores data for temporary use.

6. DISADVANTAGESOF CACHE MEMORY
Cache memory has limited capacity.
It is very expensive.

7. PRIMARY MEMORY
Primary memory holds the memory when working in the computer.
There are two types of memory;
1.RAM -RANDOM ACESS MEMORY
2.ROM -READ ONLY MEMORY

8. CHARACTERISTIC OF PRIMARY MEMORY
These are semiconductor memories
It is known as main memory.
Data is lost in case power is switched off.
It is working memory of the computer.
Faster than secondary memories.
A computer cannot run without primary memory.

9. RANDOM ACCESS MEMORY
Random access memory (RAM) is the best known form of
computer memory.
RAM is considered as volatile memory.
RAM is made up of small memory chips
RAM has two operation
Read operation –Transfer stored info to out of memory.
Write operation –Store new info

10. TYPES OF RAM
SRAM(STATICRAM) DRAM(DYNAMIC RAM)
Requires less memory Requiremore memory
Access time is low Accesstime is high
Donot refresh Need to be refresh
More power consumptionLess power consumption

12. READ ONLY MEMORY

13. ROM used to hold a program that executes automatically by the computer every
time it is turned on or reset
ROM chips contain permanently stored information.
It is NONVOLATILE.
ROM is where the basic instructions the computer needs for operation is stored.
Ex-:
moving data in and out of RAM for processing,
storing data permanently on magnetic media
displaying information on a screen
interpreting commands typed on a keyboard.

14. TYPES OF ROM
Programmable ROM (PROM).
This is basically a blank ROM chip that can be written to, but only once.
It is much like a CD-R drive that burns the data into the CD.
Erasable Programmable ROM (EPROM).
This is just like PROM
Except that you can erase the ROM by shining a special ultra-violet light into a sensor
Electrically Erasable Programmable ROM (EEPROM).
Also called flash BIOS.
This ROM can be rewritten through the use of a special software program.

15. SECONDARY MEMORY

16. Used in computer system to overcome the limitation of primary storage.
Has an operating speed far slower than that of the primary storage.
Used to stored large volumes of data on a permanent basics.
This is known as auxiliary memory.
Has virtual unlimited capacity because cost per bit of storage is very low.

17. CHARACTERISTIC OF SECONDARY
MEMORY
These are magnetic and optical memories
It is known as backup memory.
It is non-volatile memory.
Data is permanently stored even if power is switched off.
It is used for storage of data in a computer.
Computer may run without secondary memory.
Slower than primary memories

18. TYPES OF SECONDARY MEMORY

19. Thank you