TYPES OF MEMORY
Cache Memory
Cache memory is very fast semiconductor memory which can speed up the CPU's operations. It behaves as a buffer between the main memory and the CPU. It is used to store frequently accessed parts of data and programs. Those parts of data and programs are transferred to cache memory from the disk by the OS, from where they can be accessed by CPU
Advantages
The advantages of cache memory are:
∙ Cache memory is way faster than main memory(primary memory).
∙ It requires very less access time as compared to primary memory.
∙ Cache stores the program that can be executed within a small period of time.
∙ It stores data for temporary use.
Disadvantages
The disadvantages of cache memory are −
∙ Cache memory has limited/small capacity.
∙ It is very expensive.
Primary memory
It includes RAM and ROM, and is present near to the CPU on the computer's motherboard, this enables CPU to read data from primary memory quickly. It is used to store data that is frequently accessed by the CPU, so that CPU does not have to wait longer.
Primary Memory Types:
There are 2 types of primary memory mainly, which are as follows:
- RAM (Random-access memory)
The RAM (Random access memory) can be accessed in any random order.
RAM memory is very fast, and it can perform read as well as write operation, it is volatile (because all data stored in RAM memory will disappear when there is a power off) .It is very costly compared to all other types of secondary memory in terms of cost per GB. Because of the high cost of RAM in comparison to secondary memory that's why most computer systems use a combination of both primary and secondary memory.
Types of RAM
∙ DRAM: (Dynamic RAM), and it is the most common type of RAM used in computers. DRAM is made up of a capacitor and a transistor in each cell. Each DRAM cell has some charge or lack of charge held by an electrical capacitor.
∙ SRAM: (Static RAM), and it is faster than DRAM, but it is more costly and heavy, because it consists of six transistors in each cell. Because of these reasons SRAM is generally used as a data cache only or as RAM in high-end server systems. A small SRAM cache formed with most imminent data can result in significant speed improvements.
The main differences between DRAM and SRAM is that SRAM is faster than DRAM and it is costly and heavy too. SRAM is usually available in MBs, while DRAM is purchased in GBs (gigabytes).
DRAM uses more power than SRAM because it is refreshed constantly to maintain data integrity, while SRAM which is volatile, it does not need constant refreshing when it is powered up
2. ROM, [ read-only memory]
ROM is Read-only memory, and even if data can be read from this type of computer memory, data can't be written to it. It is a very fast computer's memory which is usually installed near to the CPU on the motherboard.
The ROM portion of primary memory is needed for storing an initial program called bootstrap loader, which is to start the computer software operating when power is turned on.
ROM is a non-volatile type of memory, which means that the data stored in ROM remains persistent in the memory even when there is no power. In that way, it is similar to secondary memory, which is used for long term storage.
ROM is used in some simpler electronic devices to store firmware so that they can run as the device gets power.
Types of ROM
ROM is available in different types, like PROM, EPROM, and EEPROM.
∙ MROM (Masked ROM):
The very first ROMs were hard-wired devices that contained a pre-programmed set of data or instructions. These kinds of ROMs are known as masked ROMs, which are inexpensive.
∙ PROM:
PROM is Programmable ROM, and it is completely different from the real ROM in PROM the memory is programmed (i.e. data has been written to it). During the manufacturing, a PROM is manufactured in an empty state and then programmed later using a burner or PROM programmer.
∙ EPROM:
EPROM is Erasable Programmable ROM, and data stored in an EPROM can be erased and reprogrammed easily. Erasing data from an EPROM involves removing it from the computer and exposing it to ultraviolet light (UV rays)before re-burning the memory.
∙ EEPROM:
EEPROM is Electrically Erasable Programmable ROM, and the difference between EPROM and EEPROM is that EEPROM can be erased and written by the computer in which it is installed. In that way EEPROM is not strictly read-only memory. However, in many such cases the write process is very slow, so it is normally done to update program code only such as BIOS code or firmware on an occasional basis
Differences between RAM and ROM
ROM:
∙ Non-volatile
∙ Fast to read
∙ Usually used in small quantities
∙ Cannot be written to quickly
∙ Used to store boot instructions or firmware
∙ Relatively expensive per megabyte stored compared to RAM
RAM:
∙ Volatile
∙ Fast to read and write
∙ Used as system memory to store data (including program code) that the CPU needs to process imminently
∙ Relatively cheap per megabyte stored compared to ROM, but relatively expensive compared to secondary memory.
Peripheral Devices-
A Peripheral Device is a computer device that performs input/output operations and serves as an auxiliary computer device that does not require computational power.
Peripheral devices, on the other hand, are generally not required for the computer to execute its core functions; rather, they can be viewed of as an improvement to the user's experience. A peripheral device is a device that is linked to a computer system but does not form part of the system's core design. In general, more people use the term peripheral to refer to a device that is not connected to the computer.
Classification of Peripheral devices:
It is generally classified into 3 basic categories which are given below:
1.Input Devices:
The input devices is defined as it converts incoming data and instructions into a pattern of electrical signals in binary code that are comprehensible to a digital computer.
Example:
Keyboard, mouse, scanner, microphone etc.
2. Output Devices:
An output device is generally reverse of the input process and generally translating the digitized signals into a form intelligible to the user. The output device is also performed for sending data from one computer system to another. For some time punched-card and paper-tape readers were extensively used for input, but these have now been supplanted by more efficient devices.
Example:
Monitors, headphones, printers etc.
3. Storage Devices:
Storage devices are used to store data in the system which is required for performing any operation in the system. The storage device is one of the most requirement devices and also provide better compatibility.
Example:
Hard disk, magnetic tape, Flash memory etc.
Advantage of Peripherals Devices:
Peripherals devices provides more feature due to this operation of the system is easy. These are given below:
- It is helpful for taking input very easily.
- It is also provided a specific output.
- It has a storage device for storing information or data
- It also improves the efficiency of the system.
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