Memory word definition computer

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In computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices.^[2] The term memory is often synonymous with the term primary storage or main memory. An archaic synonym for memory is store.^[3]

Computer memory operates at a high speed compared to storage that is slower but less expensive and higher in capacity. Besides storing opened programs, computer memory serves as disk cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as not needed by running software.^[4] If needed, contents of the computer memory can be transferred to storage; a common way of doing this is through a memory management technique called virtual memory.

Modern memory is implemented as semiconductor memory,^[5][6] where data is stored within memory cells built from MOS transistors and other components on an integrated circuit.^[7] There are two main kinds of semiconductor memory, volatile and non-volatile. Examples of non-volatile memory are flash memory and ROM, PROM, EPROM and EEPROM memory. Examples of volatile memory are dynamic random-access memory (DRAM) used for primary storage, and static random-access memory (SRAM) used for CPU cache.

Most semiconductor memory is organized into memory cells each storing one bit (0 or 1). Flash memory organization includes both one bit per memory cell and multi-level cell capable of storing multiple bits per cell. The memory cells are grouped into words of fixed word length, for example, 1, 2, 4, 8, 16, 32, 64 or 128 bits. Each word can be accessed by a binary address of N bits, making it possible to store 2^N words in the memory.

History[edit]

In the early 1940s, memory technology often permitted a capacity of a few bytes. The first electronic programmable digital computer, the ENIAC, using thousands of vacuum tubes, could perform simple calculations involving 20 numbers of ten decimal digits stored in the vacuum tubes.

The next significant advance in computer memory came with acoustic delay-line memory, developed by J. Presper Eckert in the early 1940s. Through the construction of a glass tube filled with mercury and plugged at each end with a quartz crystal, delay lines could store bits of information in the form of sound waves propagating through the mercury, with the quartz crystals acting as transducers to read and write bits. Delay-line memory was limited to a capacity of up to a few thousand bits.

Two alternatives to the delay line, the Williams tube and Selectron tube, originated in 1946, both using electron beams in glass tubes as means of storage. Using cathode ray tubes, Fred Williams invented the Williams tube, which was the first random-access computer memory. The Williams tube was able to store more information than the Selectron tube (the Selectron was limited to 256 bits, while the Williams tube could store thousands) and less expensive. The Williams tube was nevertheless frustratingly sensitive to environmental disturbances.

Efforts began in the late 1940s to find non-volatile memory. Magnetic-core memory allowed for recall of memory after power loss. It was developed by Frederick W. Viehe and An Wang in the late 1940s, and improved by Jay Forrester and Jan A. Rajchman in the early 1950s, before being commercialised with the Whirlwind computer in 1953.^[8] Magnetic-core memory was the dominant form of memory until the development of MOS semiconductor memory in the 1960s.^[9]

The first semiconductor memory was implemented as a flip-flop circuit in the early 1960s using bipolar transistors.^[9] Semiconductor memory made from discrete devices was first shipped by Texas Instruments to the United States Air Force in 1961. The same year, the concept of solid-state memory on an integrated circuit (IC) chip was proposed by applications engineer Bob Norman at Fairchild Semiconductor.^[10] The first bipolar semiconductor memory IC chip was the SP95 introduced by IBM in 1965.^[9] While semiconductor memory offered improved performance over magnetic-core memory, it remain larger and more expensive and did not displace magnetic-core memory until the late 1960s.^[9][11]

MOS memory[edit]

The invention of the metal–oxide–semiconductor field-effect transistor (MOSFET) enabled the practical use of metal–oxide–semiconductor (MOS) transistors as memory cell storage elements. MOS memory was developed by John Schmidt at Fairchild Semiconductor in 1964.^[12] In addition to higher performance, MOS semiconductor memory was cheaper and consumed less power than magnetic core memory.^[13] In 1965, J. Wood and R. Ball of the Royal Radar Establishment proposed digital storage systems that use CMOS (complementary MOS) memory cells, in addition to MOSFET power devices for the power supply, switched cross-coupling, switches and delay-line storage.^[14] The development of silicon-gate MOS integrated circuit (MOS IC) technology by Federico Faggin at Fairchild in 1968 enabled the production of MOS memory chips.^[15] NMOS memory was commercialized by IBM in the early 1970s.^[16] MOS memory overtook magnetic core memory as the dominant memory technology in the early 1970s.^[13]

The two main types of volatile random-access memory (RAM) are static random-access memory (SRAM) and dynamic random-access memory (DRAM). Bipolar SRAM was invented by Robert Norman at Fairchild Semiconductor in 1963,^[9] followed by the development of MOS SRAM by John Schmidt at Fairchild in 1964.^[13] SRAM became an alternative to magnetic-core memory, but requires six transistors for each bit of data.^[17] Commercial use of SRAM began in 1965, when IBM introduced their SP95 SRAM chip for the System/360 Model 95.^[9]

Toshiba introduced bipolar DRAM memory cells for its Toscal BC-1411 electronic calculator in 1965.^[18][19] While it offered improved performance, bipolar DRAM could not compete with the lower price of the then dominant magnetic-core memory.^[20] MOS technology is the basis for modern DRAM. In 1966, Robert H. Dennard at the IBM Thomas J. Watson Research Center was working on MOS memory. While examining the characteristics of MOS technology, he found it was possible to build capacitors, and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of a single-transistor DRAM memory cell.^[17] In 1967, Dennard filed a patent for a single-transistor DRAM memory cell based on MOS technology.^[21] This led to the first commercial DRAM IC chip, the Intel 1103 in October 1970.^[22][23][24] Synchronous dynamic random-access memory (SDRAM) later debuted with the Samsung KM48SL2000 chip in 1992.^[25][26]

The term memory is also often used to refer to non-volatile memory including read-only memory (ROM) through modern flash memory. Programmable read-only memory (PROM) was invented by Wen Tsing Chow in 1956, while working for the Arma Division of the American Bosch Arma Corporation.^[27][28] In 1967, Dawon Kahng and Simon Sze of Bell Labs proposed that the floating gate of a MOS semiconductor device could be used for the cell of a reprogrammable ROM, which led to Dov Frohman of Intel inventing EPROM (erasable PROM) in 1971.^[29] EEPROM (electrically erasable PROM) was developed by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at the Electrotechnical Laboratory in 1972.^[30] Flash memory was invented by Fujio Masuoka at Toshiba in the early 1980s.^[31][32] Masuoka and colleagues presented the invention of NOR flash in 1984,^[33] and then NAND flash in 1987.^[34] Toshiba commercialized NAND flash memory in 1987.^[35][36][37]

Developments in technology and economies of scale have made possible so-called very large memory (VLM) computers.^[37]

Volatile memory[edit]

Volatile memory is computer memory that requires power to maintain the stored information. Most modern semiconductor volatile memory is either static RAM (SRAM) or dynamic RAM (DRAM).^[a] DRAM dominates for desktop system memory. SRAM is used for CPU cache. SRAM is also found in small embedded systems requiring little memory.

SRAM retains its contents as long as the power is connected and may use a simpler interface, but requires six transistors per bit. Dynamic RAM is more complicated for interfacing and control, needing regular refresh cycles to prevent losing its contents, but uses only one transistor and one capacitor per bit, allowing it to reach much higher densities and much cheaper per-bit costs.^[2][23][37]

Non-volatile memory[edit]

Non-volatile memory can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, most types of magnetic computer storage devices (e.g. hard disk drives, floppy disks and magnetic tape), optical discs, and early computer storage methods such as paper tape and punched cards.^[37]

Non-volatile memory technologies under development include ferroelectric RAM, programmable metallization cell, Spin-transfer torque magnetic RAM, SONOS, resistive random-access memory, racetrack memory, Nano-RAM, 3D XPoint, and millipede memory.

Semi-volatile memory[edit]

A third category of memory is semi-volatile. The term is used to describe a memory that has some limited non-volatile duration after power is removed, but then data is ultimately lost. A typical goal when using a semi-volatile memory is to provide the high performance and durability associated with volatile memories while providing some benefits of non-volatile memory.

For example, some non-volatile memory types experience wear when written. A worn cell has increased volatility but otherwise continues to work. Data locations which are written frequently can thus be directed to use worn circuits. As long as the location is updated within some known retention time, the data stays valid. After a period of time without update, the value is copied to a less-worn circuit with longer retention. Writing first to the worn area allows a high write rate while avoiding wear on the not-worn circuits.^[38]

As a second example, an STT-RAM can be made non-volatile by building large cells, but doing so raises the cost per bit and power requirements and reduces the write speed. Using small cells improves cost, power, and speed, but leads to semi-volatile behavior. In some applications, the increased volatility can be managed to provide many benefits of a non-volatile memory, for example by removing power but forcing a wake-up before data is lost; or by caching read-only data and discarding the cached data if the power-off time exceeds the non-volatile threshold.^[39]

The term semi-volatile is also used to describe semi-volatile behavior constructed from other memory types. For example, a volatile and a non-volatile memory may be combined, where an external signal copies data from the volatile memory to the non-volatile memory, but if power is removed before the copy occurs, the data is lost. Or, a battery-backed volatile memory, and if external power is lost there is some known period where the battery can continue to power the volatile memory, but if power is off for an extended time, the battery runs down and data is lost.^[37]

Management[edit]

Proper management of memory is vital for a computer system to operate properly. Modern operating systems have complex systems to properly manage memory. Failure to do so can lead to bugs, slow performance, or takeover by viruses and malicious software.

Bugs[edit]

Improper management of memory is a common cause of bugs, including the following types:

• A memory leak occurs when a program requests memory from the operating system and never returns the memory when it’s done with it. A program with this bug will gradually require more and more memory until the program fails as the operating system runs out.
• A segmentation fault results when a program tries to access memory that it does not have permission to access. Generally, a program doing so will be terminated by the operating system.
• A buffer overflow occurs when a program writes data to the end of its allocated space and then continues to write data beyond this to memory that has been allocated for other purposes. This may result in erratic program behavior, including memory access errors, incorrect results, a crash, or a breach of system security. They are thus the basis of many software vulnerabilities and can be maliciously exploited.

Early computer systems[edit]

In early computer systems, programs typically specified the location to write memory and what data to put there. This location was a physical location on the actual memory hardware. Early computers did not have the complex memory management systems used today.

This approach has its pitfalls. If the location specified is incorrect, this will cause the computer to write the data to some other part of the program. The results of an error like this are unpredictable. In some cases, the error might overwrite memory used by the operating system. Hackers can take advantage of this lack of protection to create viruses and malware.

Virtual memory[edit]

Virtual memory is a system where physical memory is managed by the operating system typically with assistance from a memory management unit. It allows multiple types of memory to be used. For example, some data can be stored in RAM while other data is stored on a hard drive (e.g. in a swapfile), functioning as an extension of the cache hierarchy. This offers several advantages. Computer programmers no longer need to worry about where their data is physically stored or whether the user’s computer will have enough memory. The operating system will place actively used data in RAM, which is much faster than hard disks. When the amount of RAM is not sufficient to run all the current programs, it can result in a situation where the computer spends more time moving data from RAM to disk and back than it does accomplishing tasks; this is known as thrashing.

Protected memory[edit]

Protected memory is a system where each program is given an area of memory to use and is prevented from going outside that range. If the operating system detects that a program has tried to alter memory that does not belong to it, the program is terminated (or otherwise restricted or redirected). This way, only the offending program crashes, and other programs are not affected by the misbehavior (whether accidental or intentional). Use of protected memory greatly enhances both the reliability and security of a computer system.

Without protected memory, it is possible that a bug in one program will alter the memory used by another program. This will cause that other program to run off of corrupted memory with unpredictable results. If the operating system’s memory is corrupted, the entire computer system may crash and need to be rebooted. At times programs intentionally alter the memory used by other programs. This is done by viruses and malware to take over computers. It may also be used benignly by desirable programs which are intended to modify other programs, debuggers, for example, to insert breakpoints or hooks.

See also[edit]

• Memory geometry
• Memory hierarchy
• Memory organization
• Processor registers store data but normally are not considered as memory, since they only store one word and do not include an addressing mechanism.

Notes[edit]

References[edit]

Further reading[edit]

• Miller, Stephen W. (1977), Memory and Storage Technology, Montvale.: AFIPS Press

• Memory and Storage Technology, Alexandria, Virginia.: Time Life Books, 1988

Memory is the electronic holding place for the instructions and data a computer needs to reach quickly. It’s where information is stored for immediate use. Memory is one of the basic functions of a computer, because without it, a computer would not be able to function properly. Memory is also used by a computer’s operating system, hardware and software.

There are technically two types of computer memory: primary and secondary. The term memory is used as a synonym for primary memory or as an abbreviation for a specific type of primary memory called random access memory (RAM). This type of memory is located on microchips that are physically close to a computer’s microprocessor.

If a computer’s central processer (CPU) had to only use a secondary storage device, computers would become much slower. In general, the more memory (primary memory) a computing device has, the less frequently the computer must access instructions and data from slower (secondary) forms of storage.

Memory vs. storage

The concept of memory and storage can be easily conflated as the same concept; however, there are some distinct and important differences. Put succinctly, memory is primary memory, while storage is secondary memory. Memory refers to the location of short-term data, while storage refers to the location of data stored on a long-term basis.

Memory is most often referred to as the primary storage on a computer, such as RAM. Memory is also where information is processed. It enables users to access data that is stored for a short time. The data is only stored for a short time because primary memory is volatile, meaning it isn’t retained when the computer is turned off.

The term storage refers to secondary memory and is where data in a computer is kept. An example of storage is a hard drive or a hard disk drive (HDD). Storage is nonvolatile, meaning the information is still there after the computer is turned off and then back on. A running program may be in a computer’s primary memory when in use — for fast retrieval of information — but when that program is closed, it resides in secondary memory or storage.

How much space is available in memory and storage differs as well. In general, a computer will have more storage space than memory. For example, a laptop may have 8 GB of RAM while having 250 GB of storage. The difference in space is there because a computer will not need fast access to all the information stored on it at once, so allocating approximately 8 GB of space to run programs will suffice.

The terms memory and storage can be confusing because their usage today is not always consistent. For example, RAM can be referred to as primary storage — and types of secondary storage can include flash memory. To avoid confusion, it can be easier to talk about memory in terms of whether it is volatile or nonvolatile — and storage in terms of whether it is primary or secondary.

How does computer memory work?

When a program is open, it is loaded from secondary memory to primary memory. Because there are different types of memory and storage, an example of this could be a program being moved from a solid-state drive (SSD) to RAM. Because primary storage is accessed faster, the opened program will be able to communicate with the computer’s processor at quicker speeds. The primary memory can be accessed immediately from temporary memory slots or other storage locations.

Memory is volatile, which means that data in memory is stored temporarily. Once a computing device is turned off, data stored in volatile memory will automatically be deleted. When a file is saved, it will be sent to secondary memory for storage.

There are multiple types of memory available to a computer. It will operate differently depending on the type of primary memory used, but in general, semiconductor-based memory is most associated with memory. Semiconductor memory will be made of integrated circuits with silicon-based metal-oxide-semiconductor (MOS) transistors.

Types of computer memory

In general, memory can be divided into primary and secondary memory; moreover, there are numerous types of memory when discussing just primary memory. Some types of primary memory include the following

• Cache memory. This temporary storage area, known as a cache, is more readily available to the processor than the computer’s main memory source. It is also called CPU memory because it is typically integrated directly into the CPU chip or placed on a separate chip with a bus interconnect with the CPU.
• RAM. The term is based on the fact that any storage location can be accessed directly by the processor.
• Dynamic RAM. DRAM is a type of semiconductor memory that is typically used by the data or program code needed by a computer processor to function.
• Static RAM. SRAM retains data bits in its memory for as long as power is supplied to it. Unlike DRAM, which stores bits in cells consisting of a capacitor and a transistor, SRAM does not have to be periodically refreshed.
• Double Data Rate SDRAM. DDR SRAM is SDRAM that can theoretically improve memory clock speed to at least 200 MHz.
• Double Data Rate 4 Synchronous Dynamic RAM. DDR4 RAM is a type of DRAM that has a high-bandwidth interface and is the successor to its previous DDR2 and DDR3 versions. DDR4 RAM allows for lower voltage requirements and higher module density. It is coupled with higher data rate transfer speeds and allows for dual in-line memory modules (DIMMS) up to 64 GB.
• Rambus Dynamic RAM. DRDRAM is a memory subsystem that promised to transfer up to 1.6 billion bytes per second. The subsystem consists of RAM, the RAM controller, the bus that connects RAM to the microprocessor and devices in the computer that use it.
• Read-only memory. ROM is a type of computer storage containing nonvolatile, permanent data that, normally, can only be read and not written to. ROM contains the programming that enables a computer to start up or regenerate each time it is turned on.
• Programmable ROM. PROM is ROM that can be modified once by a user. It enables a user to tailor a microcode program using a special machine called a PROM programmer.
• Erasable PROM. EPROM is programmable read-only memory PROM that can be erased and re-used. Erasure is caused by shining an intense ultraviolet light through a window designed into the memory chip.
• Electrically erasable PROM. EEPROM is a user-modifiable ROM that can be erased and reprogrammed repeatedly through the application of higher than normal electrical voltage. Unlike EPROM chips, EEPROMs do not need to be removed from the computer to be modified. However, an EEPROM chip must be erased and reprogrammed in its entirety, not selectively.
• Virtual memory. A memory management technique where secondary memory can be used as if it were a part of the main memory. Virtual memory uses hardware and software to enable a computer to compensate for physical memory shortages by temporarily transferring data from RAM to disk storage.

Timeline of the history and evolution of computer memory

In the early 1940s, memory was only available up to a few bytes of space. One of the more significant signs of progress during this time was the invention of acoustic delay line memory. This technology enabled delay lines to store bits as sound waves in mercury, and quartz crystals to act as transducers to read and write bits. This process could store a few hundred thousand bits. In the late 1940s, nonvolatile memory began to be researched, and magnetic-core memory — which enabled the recall of memory after a loss of power — was created. By the 1950s, this technology had been improved and commercialized and led to the invention of PROM in 1956. Magnetic-core memory became so widespread that it was the main form of memory until the 1960s.

Metal-oxide-semiconductor field-effect transistors, also known as MOS semiconductor memory, was invented in 1959. This enabled the use of MOS transistors as elements for memory cell storage. MOS memory was cheaper and needed less power compared to magnetic-core memory. Bipolar memory, which used bipolar transistors, started being used in the early 1960s.

In 1961, Bob Norman proposed the concept of solid-state memory being used on an integrated circuit (IC) chip. IBM brought memory into the mainstream in 1965. However, users found solid-state memory to be too expensive to use at the time compared to other memory types. Other advancements during the early to mid-1960s were the invention of bipolar SRAM, Toshiba’s introduction of DRAM in 1965 and the commercial use of SRAM in 1965. The single-transistor DRAM cell was developed in 1966, followed by a MOS semiconductor device used to create ROM in 1967. From 1968 to the early 1970s, N-type MOS (NMOS) memory also started to become popularized.

By the early 1970s, MOS-based memory started becoming much more widely used as a form of memory. In 1970, Intel had the first commercial DRAM IC chip. One year later, erasable PROM was developed and EEPROM was invented in 1972.

This was last updated in October 2020

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What is a Computer Memory:: It stores or saves instructions and results, and the results can be saved permanently as well as temporarily.

The data or instructions once saved can be retrieved or recalled or reviewed whenever the user demands.

They can store a huge amount of data and information as per requirements. The user can use the data whenever needs.

The Computer Hard Disk used as memory has the capability for storing volumes of data such as songs, movies, pictures, and software’s one can easily get access to this data whenever or wherever the user demands.

Users can rest sure of their data, as the data is stored almost permanently.

The computer memory can be classified in Four different types 

• Internal Processor Memory
• Main memory | RAM (Random Access Memory) | Primary Memory
• Cache Memory
• Storage | Secondary Memory

1. Internal Processor Memory.

These tiny high-speed registers live internally in a CPU or Processor, these registers are used and utilized in storing the data or instruction and information temporarily before the data is processed further where real processing and preparing takes place.

These registers are placed inside ALU and control unit, they are high-speed and perform arithmetical and logical operations at enormous speed.

They store or hold the data or instructions and information temporarily during the process, registers are extremely efficient.

Registers work under the control of the control unit for accepting and storing the data or instructions and information.

The speed or the processing and handling strength of the computer system relies upon the size, capacity, and limit of registers.

A few registers can hold up to 8 bits to 16 bits of data.

Yet with the improvement in cutting-edge innovation, the microchip or microprocessor has been created, designed, and developed to make the operation and applications work significantly speedier than some time before.

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The more up-to-date microprocessor or a microchip can hold 32-bit to 128-bit registers, as this registers capacity of holding the data has been increased so the computer system speed for accessing, handling, preparing, and processing the data speed has been dramatically increased and expanded.

Different computer types uses and utilizes different types of registers relying on their size, abilities and capabilities. 

These cache memory stores the data and information temporarily and they are faster compared to main memory, as they reside or dwells inside the processor their speed of transferring the data to other location are faster than any other “computer memory“.

2. Primary or Main Memory.

Primary or Main Memory is additionally called “SEMICONDUCTOR MEMORY”. 

This is likewise a Temporary memory that holds or saves data and information temporarily, as when there is a power failure or no power the data or information is lost.

They work or hold only on the present data which is being used and utilized by a computer system. They are not as fast as the registers.

The semiconductor memory is faster, smaller, lighter, and consumes less power compared to secondary storage.

They have a limited capacity, as well as they are very costly and can store only a couple of bytes of data.

They are essential memories to a computer if they are removed from a computer it fails to start or boot normally.

Each and every computer needs a primary memory to work properly.

The Capacity of primary memory is calculated in MB (Mega-Bytes) and GB (Giga-Bytes). nowadays they come in huge capacities ranging from 2 GB to 16 GB.

The main memory is further classified into two categories

• RAM (RANDOM ACCESS MEMORY)
• ROM (READ-ONLY MEMORY)

3. RAM (RANDOM ACCESS MEMORY)

The RAM Is known as “Random Access Memory”. 

This is a volatile memory which means it cannot store or saves the data or instruction or set of information once the power is off.

They are fast, less expensive & light.

RAM can transfer or exchange data from and to the CPU considerably speedier than secondary storage.

The RAM is placed inside the computer system to be precise they are installed on a computer motherboard and it is also a primary reason for computer speed.

It is used for storing all active programs or instructions with the goal that it can be additionally exchanged for CPU for the additional process.

The technology used in RAM is based on semiconductor integrated circuits. RAM is divided into two more categories

1. Static Ram
2. Dynamic Ram

Static RAM:: The static Ram stores binary information in clocked sequential circuits. It is comprised of flip-flops and stores a touch of voltages.

It is a volatile or unstable memory if the power is from the data or instructions is destroyed. This kind of memory does not require refreshing.

Dynamic RAM:: Dynamic RAM stores binary information in the form of electric charges that are connected to capacitors that are inside the chip.

This type of Ram Consumes less power and is capable of storing or holding more data and information compared to static RAM.

4. ROM (READ-ONLY MEMORY).

ROM Stands for “READ ONLY MEMORY” they are non-volatile or non-unstable if the power is off they can still store the data permanently.

They can be used as permanent storage.

Users can not manipulate the data which is inside this memory only the manufacturer or programmers writes programs or instructions inside them.

which are used to boot the computer or operating systems when the computer is powered on.

ROM are of different Types

• PROM
• EPROM
• EEPROM

PROM

PROM stands for “Programmable Read-Only Memory” it is also a type of non-volatile memory.

which once programmed or customized then the set of instructions or information stored cannot be deleted or updated or refreshed.

Computer Programmers or software developers write and compose programs or codes in this chip in such a fashion to receive the desired functionality, special equipment is used to write programs inside the chip.

EPROM

EPROM stands for “Erasable Programmable Read-Only Memory” as the name suggests the programs which had been written and composed by computer programmers can be deleted or updated according to the necessities.

One simply needs to uncover this chip to High Ultraviolet light for over 20 minutes to delete the information.

Once exposed they can be reused after reprogrammed

They should not be overexposed to avoid damage.

You cannot delete, or erase a single content from them if you try to do it the whole data or information inside the chip gets deleted or erased.

This type of memory is broadly used as they are cheap and reliable.

EEPROM

EEPROMS stands for “Electrically Erasable Programmable Read-Only Memory” to erase or delete the information or data inside them one should take the memory outside the PCB (Printed Circuit Board).

As the time required for erasing the information is significantly speedier the EPROMs.

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CACHE MEMORY of Computer System

Cache memory dwells between primary memory and CPU [Central Processing Unit]. It is extremely expensive therefore the manufacturer uses it in low numbers.

They are fast and reliable. They are likewise called high-speed semiconductors.

They are primarily responsible for accelerating the CPU.

They hold or store the data which is frequently used by “COMPUTER PROCESSOR”.

This program or information is transferred and exchanged from disk to cache memory with the assistance of the operating system so that Processor can access them.

They are considerably much faster than the main memory, and the data exchanging time is less as compared to the main memory.

This is one of the fastest computer memory used in computer systems.

The powerful computer uses more cache memory to speed up the process of information transferring and exchanging.

10 Characteristics of Primary Memory

#	Characteristics of Primary Memory
1	They are faster memory than the secondary memory of computers.
2	They are volatile memory in nature also called “Semiconductor Memory“.
3	They are expensive in nature.
4	They can be accessed directly with the CPU {Central Processing Unit}.
5	They are the most essential memory in computer systems.
6	The data and information can be transferred from one location to another with speed and accuracy.
7	They are volatile in nature. The data and information once lost can not be recovered.
8	They are crucial Memory of computer system & the computer cannot function correctly without them.
9	They are compact.
10	The primary Memory of a computer system holds all the major applications of OS.

Functions of Primary Memory

• Primary Memory is capable of communicating directly with the CPU [Central Processing Unit] without any intervention.
• They are built to store data, instruction, and information that is currently in process.
• They stored data and instructions temporarily.
• The operating system’s crucial and important files dwell inside the main memory or primary memory temporarily for system start-up or booting.
• Application Software and Utility Software require primary memory for proper functionality.

Examples of Primary Memory

There are various examples of primary memory that are mentioned below.

• RAM
• ROM
• SDRAM
• DRAM
• SRAM
• PROM
• EPROM
• EDORAM
• DDR SDRAM

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Storage Memory | Secondary Memory of Computer

Secondary Storage is also called “AUXILLARY MEMORY”. 

They are also called “PERMANENT MEMORY” as they are non-volatile in nature the data stored in them is stored permanently and the user can get access to their data any time the user requests.

If the power is off they still don’t lose the data because of its non-volatile nature.

They are the slowest and the least expensive type of PC memory as they can’t directly and straightforwardly get access to the CPU they utilize the primary memory for storing and holding their information partially.

They can store large volumes of data permanently, and whenever the computer system requires the data it can be served as primary memory for advanced processing.

The different types of secondary Memory which are used in computer systems 

• Magnetic Tapes
• Hard-disk
• Floppy Disk
• Zip Drives
• Optical Disk

Types of Secondary Memory

1. Fixed Storage
2. Removal Storage

Examples of Secondary Memory

1. SDD [Solid State Drives]
2. Flash Drives
3. NAS [Network Attached Storage]
4. SAN [Storage Area Network]
5. Cloud Storage
6. Magnetic Tapes
7. Magnetic Disk
8. Hard-Disk
9. Floppy Disk
10. Zip Drives
11. Optical Disk
12. Pen Drives

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7 Characteristics of Secondary Memory of Computer System

#	Characteristics of Secondary Storage Devices
1	Secondary Storage Memory is non-volatile.
2	They are fast memory but not as speedy as primary memory.
3	The data and information stored in secondary memory like a hard disk or SSD can be saved permanently.
4	They are inexpensive compared to primary memory.
5	They are portable and can be transferred from one location to another.
6	They can store data in any form, like songs, movies, software, files, etc.
7	They are readily available in the market with different storage capacities.

Advantages & Disadvantages of Cache Memory

#	Advantages	Disadvantages
1	A cache is faster and has smaller memory and is used more frequently.	Expensive memory compared to others.
2	A primary cache has a less access time comparable to a processor register and it is always placed on the processor chip.	It is a Volatile Memory.
3	It is generally placed between the primary cache.	The storage capacity is completely in use.
4	Cache memory is high-speed semiconductor memory that is responsible for the CPU.	The increased chip area is required for the memory system.
5	It consumes less access time as compared to main memory.	Cache data is stored as long as the computer power is on.

Differences Between Internal & External Memory

#	Internal Memory	External Memory
1	Internal memory is Volatile.	External memory is Non- Volatile.
2	Also Known as “Primary Memory” or “Main Memory” or “Semiconductor Memory”.	External or secondary memory is also called “AUXILLARY MEMORY” and “PERMANENT MEMORY.”
3	They are installed internally.	They are attached using cables and wires.
4	Low Storage Capacity.	Enormous Storage Capacity.
5	They are faster compared to external memory.	They are slower than internal memory.
6	Examples of internal memory RAM (RANDOM ACCESS MEMORY) ROM (READ-ONLY MEMORY)	Examples of Secondary storage Computer Hard Disk Drive. Pen Drives. SSD {Solid State Drives}. Optical Disks. Cloud Storage
7	They are expensive.	They are cheaper.

Top Memory Manufacturer

#	Company
1	Corsair.
2	Kingston.
3	G.SKILL.
4	Transcend.
5	IBM.

Frequently Asked Questions [FAQs] on Computer Memory

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What Does Memory Mean in Computers?

Memory is internal storage areas in the computer system. The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.

Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.

There are several different types of memory:

RAM (random-access memory): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost.

ROM (read-only memory): Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to.

PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile.

EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light.

EEPROM (electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge.

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