In this post, we learn about what is memory in computer and different types of memory in computer.
Table of Contents
what is memory in computer
Memory is the major and significant component present in a computer. Memory is used to hold the data and the instructions that are being currently used by the CPU. The main memory is the memory that is present in the motherboard. Memory greatly influences the performance of the system. In this post, we learn about what is memory in the computer.
Some of the features of memory are explained as follows:
Performance: The performance of a system is greatly influenced by the type of memory and the amount of memory available in the system. It is significant that if the available memory is insufficient then the performance of the machine is greatly reduced to even 50%.
Software Support: The amount of memory that is needed to run different software programs varies. If any new software is installed it is necessary to know the amount of memory that is required by them.
Reliability and Scalability: If the memory is bad or corrupted then it would lead to many serious and unexpected problems. Hence the stability and the reliability of the system are greatly affected.
Upgradeability: The memory used in the computer should be upgradeable. Many different types of memory are available and hence it is necessary to make the best choice by selecting the memory which could be effectively used for migration to the future system. The memory that is selected for usage should operate well even in the upgraded motherboard.
Types of memory in computer
Memory can be mainly classified as primary memory and secondary memory.
Primary memory
Primary memory refers to the storage which is directly accessible by the CPU. Primary memory is faster than secondary memory.
Secondary memory
Secondary memory cannot be directly accessed by the CPU. Secondary storage is used to store large amounts of data, but the access speed is less. Secondary storage holds the data which is not in active use. Secondary memory can be classified as Electromagnetic storage and optical storage. Examples of electromagnetic storage include floppy disk, hard disk, and optical storage include the CD-ROM, DVD, etc. The table below summarizes the difference between primary storage and secondary storage.
| Primary memory | Secondary memory |
| Storage that is directly accessible by the CPU. | Not accessible directly by the CPU. Needs the help of I/O channels for accessing the CPU. |
| Provides fast access. | Provides slow access. |
| Can store less amount of data. | Can store a large amount of data. |
Memory can be also classified as volatile memory and non-volatile memory.
Volatile memory-RAM is volatile which means the data stored in them is lost when the power is switched off. Continuous power supply is necessary for a volatile memory to hold the data. When the power is switched off the data is lost. Hence volatile storage is used to store data temporarily.
The difference between volatile and non-volatile storage can be summarized as follows
Non-volatile-Nonvolatile storage retains the data even in the absence of power. Read-only Memory (ROM) and other secondary storage devices are examples of non-volatile memory.
| Volatile memory | Non-volatile memory |
| The memory holds the data as long as the power is present. The data is lost if the power supply is switched off. | Needs no power supply to retain the data. The data is stored permanently. |
| Example Random Access Memory (RAM) | Example ROM, Hard Disk, Floppy Disk. |
Primary memory can be classified primarily as Random Access Memory (RAM) and Read Only Memory (ROM).
Random Access Memory (RAM)
RAM is used to store the user program and data for processing. RAM is a volatile memory. The data is lost if the power is switched off. RAM is faster than ROM since RAM provides random access. The access time required to access the data stored in any location is the same irrespective of the memory location. RAM is a read/write memory where it is possible to both read and write data into them dynamically.
RAM can be broadly classified into Static RAM (SRAM) and Dynamic RAM (DRAM).
Static RAM (SRAM)-Static RAM is made of flip-flops. SRAM does not need any refreshing circuit and is comparatively costly. SRAM is used in cache memory and is in buffers.
Dynamic RAM (DRAM)-Dynamic RAM is made of capacitors. DRAM needs a separate refreshing circuit to hold the data. The user program and data are stored in DRAM.
Read-only Memory (ROM)
Read-only memory is a type of memory used in computers. The data can be read from ROM but cannot be written into it. ROM is non volatile ROM has some important characteristics like-
Permanence – The data stored in ROM is always stored and is not lost if the power is switched off. ROM is non-volatile storage. The data present in ROM is not erased. Hard disk is an example of non-volatile storage. Once a program is stored on a hard disk, it is available for the next time even when it is switched off. Hence it keeps the data permanently.
Security – Since ROM is read-only Memory the data stored in them is secure and cannot be deleted easily. The data is stored in ROM is highly secure and viruses or any other Malicious code cannot be deleted or modified from the contents stored in them.
Types of ROM
ROM can be classified into four different types. They are
- ROM
- Programmable ROM (PROM)
- Erasable Programmable ROM (EPROM)
- Electrically Erasable Programmable ROM (EEPROM)
ROM
Read-only memory can be programmed only once by the manufacturer, It can be used only for specific applications and the function of the chip cannot be changed. This is used for static applications. A best example of ROM is the commercial software CD-ROM which you procure from a shop, The application present in the CD alone can be run several times and nothing can be edited or written to it.
Programmable ROM (PROM)
PROM is a type of ROM that can be written only once using some specialized equipment but can be read any number of times, Writing content into PROM is called burning, This is similar to a blank CD-ROM which can be written once to store the programs created by the users and then can be read by others. Burning a CD-ROM is an example of programming ROM
Erasable Programmable ROM (EPROM)
EPROM is a type of ROM that can be erased and programmed several times/EPROM chip is provided with a glass window through which the chip can be programmed any number of times by passing Ultraviolet rays through them for a defined amount of time This type of ROM is useful than PROM since it can be programmed and used any number of times.
Memory Read Operation
In memory read operation, the address is placed on the address bus and the control signal memory read is issued by the processor. The memory controller then locates the corresponding row and column and places the data available in that location on the data bus. The data present in the data bus is now available for the processor Memory read is the process of reading data from memory.
Memory Write Operation
In memory write operation, the address is placed on the address bus and the control signal is given to the memory to write the data in the location given by the address bus. After the completion of one memory access, it is not feasible to start the next memory access immediately. Instead. the next memory access can start only after a certain period of time called the memory refresh time.
What is Memory in computer and lts Specification
Storage capacity – Storage capacity is the maximum amount of data that a storage medium can hold. The storage capacity is expressed in bytes
Throughput-Throughput is the speed at which the data can be read or written to the storage medium. It is expressed in Megabytes/second
Memory Addressing – memory is arranged in an XY grid-like pattern with rows and columns. Each cell holds one bit of information either 0 or 1.
The data present in the memory cell can be read by sending the row address first. The row address is first placed on the address bus is sent to the memory chip and is latched. The Row Access Select (RAS) signal is activated.
The circuit then waits for 15 ns and allows the row address to be latched. After 15 ns, the column address is placed on the address bus and the Column Access Select (CAS) signal is activated. Then the circuit waits for some to get the data that is stored in the memory cell. The data stored in the cell will be now available as the high or low voltage on the data bus.
Advantages of Computer Memory
Storage Capacity. Storage capacity is crucial in storing and retrieving data on your computer.
Program Execution. So we’ve already discovered that more computer memory allows for faster access and retrieval of data.
Speed and Efficiency.
Data Retrieval.
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