MEMORY
Memory is the storage area of computer where all the inputs (data as well as instructions ) are stored before processing and the outputs are stored after processing of inputs.
As there can be many input devices attached with a computer, all these devices may supply input at a time but the CPU may not be able to process all the inputs in one go. Therefore, a place is required to queue up these inputs and then process them one by one. All these inputs are queued up in the memory. The same case is there with the outputs produced by the CPU.
If the output device is busy in producing an output, the other outputs are queued up in the memory.
The memory of a computer can be divided into two broad categories:
As there can be many input devices attached with a computer, all these devices may supply input at a time but the CPU may not be able to process all the inputs in one go. Therefore, a place is required to queue up these inputs and then process them one by one. All these inputs are queued up in the memory. The same case is there with the outputs produced by the CPU.
If the output device is busy in producing an output, the other outputs are queued up in the memory.
The memory of a computer can be divided into two broad categories:
- Primary Storage.
- Secondary Storage.
PRIMARY STORAGE
Primary storage, also known as main storage or main memory is a direct access storage device, consisting of a number of storage locations. Each location in the storage has a unique number, called Storage Address. The system assigns a unique memory location to each data element. Once the data element is assigned to the location, the system accesses it directly by means of the address of the particular storage location.
The various types of primary storage are:
Whenever user enters any kind of data into the computer system,it moves into primary memory for storage. This type of primary memory is known as RAM. It is the most randomly access storage type among all types of storage. The main features of RAM are:
The various types of primary storage are:
- RAM (Random Access Memory)
- ROM(Read Only Memory)
- CACHE Memory
- Virtual Memory
Whenever user enters any kind of data into the computer system,it moves into primary memory for storage. This type of primary memory is known as RAM. It is the most randomly access storage type among all types of storage. The main features of RAM are:
- The word "random" refers to the fact that any piece of data can be returned quickly, and in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.
- RAM is volatile in nature i.e. once the system is switched off, the contents of RAM will automatically be erased.
- RAM stores the data purely on temporary basis i.e. user can remove the previous data and write new information into it whenever required.
- RAM is small, both in terms of its physical size and in the amount of data it can hold.
- Every computer application demands a particular amount of memory from RAM in order to execute.
- RAM is also referred as read and write memory of the computer i.e. user can read the data from RAM as well as write the data into RAM.
- The storage capacity of RAM varies. Today, it is available in Megabytes(MB). (Like- 512 MB) and also in Gigabytes (GB) (Like- 1 GB 2 GB 4 GB)
TYPES OF RAM
There are mainly two types of RAM:
The word "static" indicates that the memory retains its contents as long as power remains applied, unlike dynamic RAM (DRAM) that needs to be periodically refreshed. Data are lost when the circuit gets powered down, however, which makes static RAM a volatile memory.
The Static RAM consumes more power. There are six transistors needed to form a memory cell of static RAM. It is more expensive and holds less data than dynamic RAM.
DYNAMIC RAM
The term "dynamic" indicates that the memory must be constantly refreshed because Dynamic RAM (DRAM) loses its stored information in a few milliseconds even though its power supply is ON. It stores information in the form of charge on a capacitor, which leaks away in a very short time. Therefore its contents must be periodically refreshed after every two milliseconds. The Dynamic RAM consumes less power and is cheaper than the Static RAM.
There are mainly two types of RAM:
- Static RAM
- Dynamic RAM
The word "static" indicates that the memory retains its contents as long as power remains applied, unlike dynamic RAM (DRAM) that needs to be periodically refreshed. Data are lost when the circuit gets powered down, however, which makes static RAM a volatile memory.
The Static RAM consumes more power. There are six transistors needed to form a memory cell of static RAM. It is more expensive and holds less data than dynamic RAM.
DYNAMIC RAM
The term "dynamic" indicates that the memory must be constantly refreshed because Dynamic RAM (DRAM) loses its stored information in a few milliseconds even though its power supply is ON. It stores information in the form of charge on a capacitor, which leaks away in a very short time. Therefore its contents must be periodically refreshed after every two milliseconds. The Dynamic RAM consumes less power and is cheaper than the Static RAM.
ROM (READ ONLY MEMORY)- NON-VOLATILE MEMORY
ROM is "built-in" computer memory also known as Firmware. Instructions that are required all the time in the system for running the computer are stored in the ROM. The main features of ROM are:
ROM is "built-in" computer memory also known as Firmware. Instructions that are required all the time in the system for running the computer are stored in the ROM. The main features of ROM are:
- It consists of small chip located near CPU on the motherboard.
- It is the read only memory i.e. user can only read the instructions but cannot write into it.
- The instructions stored in it are permanent in the nature and are usually designed by the manufacturer of the computer.
- ROM is non-volatile in nature i.e. data does not get erased when the computer's power is switched off.
- The memory organization of ROM is exactly the same as that of RAM.
- ROM chips are used not only in computers, but in most other electronic items as well(like: calculator).
- PROM(Programmable Read Only Memory).
- E PROM(Erasable Programmable Read Only Memory).
- E E PROM(Electrically Erasable Programmable Read Only Memory).
CACHE MEMORY
The process accesses the main memory to read the instructions. The speed at which the processor executes the instructions is much faster than the speed at which the instructions are transferred from the main memory. This type of memory is called Cache Memory/Buffers. Some of the main features of Cache memory are:
The process accesses the main memory to read the instructions. The speed at which the processor executes the instructions is much faster than the speed at which the instructions are transferred from the main memory. This type of memory is called Cache Memory/Buffers. Some of the main features of Cache memory are:
- Cache memory is small, fast and expensive type of storage that is placed between the CPU and the main memory.
- The CPU transfers the instructions from the cache memory towards its processing area at the very high speed, thus it improves the processing speed. Hence, instead of every time reading from the main memory, now CPU first the data check the cache memory for the required data and if CPU finds the data there, it is called Cache Hit and if the required data is not present in cache, CPU then reads it from main memory. This state is called Cache Miss.
- Cache memory makes main memory appear to be faster and larger than it really is.
- It is very expensive as compared to the main memory and hence its size is normally very small.
VIRTUAL MEMORY
When the computer is to process a large amount of data, some times the size of main memory or RAM becomes inadequate or not sufficient to store that data. To overcome this problem the technique of virtual memory is used.
In this case, operating system approaches to the secondary storage (hard disk) and borrows the required amount of memory from it and utilizes it as a main memory or RAM for processing the data. This borrowed or shared memory is called virtual memory.
When the computer is to process a large amount of data, some times the size of main memory or RAM becomes inadequate or not sufficient to store that data. To overcome this problem the technique of virtual memory is used.
In this case, operating system approaches to the secondary storage (hard disk) and borrows the required amount of memory from it and utilizes it as a main memory or RAM for processing the data. This borrowed or shared memory is called virtual memory.
Write by Ditender Singh and
Powered by Weebly
Powered by Weebly