Memory that holds data while the computer is in operation

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1. Career development
2. 14 Types of Computer Memory: What You Should Know

By Indeed Editorial Team

Published July 13, 2021

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

There are many elements involved in ensuring a computer operates at optimum capacity. In order to function properly, computers require memory to hold information that the central processing unit uses to process and complete instructions. If you're interested in a career in computer science, then consider learning more about computer memory and its role in digital devices. In this article, we discuss what computer memory is, why it's important and 14 types of computer memory.

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What is computer memory?

Computer memory is an internal or external system that stores data and instructions on a device. It consists of several cells, called memory cells, that each have a unique identification number. The central processing unit (CPU), which reads and executes instructions, selects specific cells to read or write data depending on the task the user is asking the computer to do. There are many kinds of memory you can use depending on how much you need and the type of device you're using.

Why is computer memory important?

Computer memory is important because devices cannot process tasks without it. Memory ensures a device turns on and functions properly. In addition, it keeps your computer running quickly and allows you to use multiple applications at once. If you want to store data for later use, you also use certain types for that purpose.

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14 types of computer memory

Here is a list of 14 types of computer memory:

1. Internal

Internal memory, also known as primary memory, stores small amounts of data that the computer can access while you're actively using it. Internal memory consists of chips connected to the motherboard and needs to be connected directly to the device in order to use it. There are two basic types of internal memory called RAM and ROM, and those have their own subsets of memories.

2. RAM

Random access memory (RAM) is the primary internal memory of the central processing unit (CPU). Your electronic device uses it for storing temporary data. It does this by providing applications with a place to store data you're actively using so that it can quickly access the data. The amount of RAM on your device controls its performance and speed. If you don't have enough RAM, it may process programs slowly which can affect the output and speed with which you can use the computer.

RAM also has "volatile memory" because it loses the data it was storing if you turn off the device. For example, if you're on your laptop using the internet browser and your computer gets turned off, it may not have saved the web pages you were previously using because RAM only stores that information temporarily.

3. DRAM

Dynamic random access memory (DRAM) is one of the two specifics types of RAM seen in modern devices, such as laptops, desktops, portable devices and gaming systems. It's the more affordable of the two types of RAM and produces high-capacity memory. It's made of two components, transistors and capacitors, which require a recharge every few seconds to retain its data. Like RAM, it also loses data when it loses power and has volatile memory.

4. SRAM

Static random access memory (SRAM) is the second type of RAM and stores data as long as there is power in the system, unlike DRAM which is refreshed much more frequently. Because it holds power longer, it's more expensive than DRAM, which typically makes it not as widely used. Users generally use SRAM for cache memory, which makes it a faster form of memory than DRAM.

5. ROM

Read-only memory (ROM) is another type of primary internal memory, but unlike RAM, ROM is non-volatile and stores data permanently. It does not depend on the device to be turned on in order to save data. Instead, a programmer writes the data into individual cells using binary code, which represents text using the "1" and "0" two-symbol system. Because you cannot alter the data on ROM, you can use this type of memory for aspects that don't change, such as the boot-up of software or firmware instructions, which help a device function properly.

Related: What Is ROM and How Is It Different From RAM?

6. PROM

Programmable read-only memory (PROM) is a type of ROM that begins as memory with no data on it. A user can write data onto the chip using a special device called a PROM programmer. Like ROM, data is permanent once a user has written it onto the chip. This type of memory may be useful to programmers who would like to create specific firmware for a chip and use it to alter the typical function of a system.

7. EPROM

Erasable programmable read-only memory (EPROM) is another type of ROM chip that users can write data on as well as erase old data and reprogram it. You can erase the current data by using ultraviolet (UV) light in the form of a quartz crystal window at the top of the chip. After you've erased the data, you can use the PROM programmer to reprogram it. You can only erase data from an EPROM chip a certain number of times because excessive erasing can damage the chip and make it unreliable for future use.

8. EEPROM

Electrically erasable programmable read-only memory (EEPROM) is the final type of non-volatile ROM chip that usually replaces the need for PROM or EPROM chips. This type of memory also allows users to erase and reprogram data onto the chip, but does so using an electric field and is much quicker at erasing data than the EPROM. In addition, you can conveniently erase data while the chip is still inside the computer, whereas EPROM chips need to be taken out of the computer to erase it.

9. Cache

Cache memory is an internal high-speed semiconductor memory that stores instances of data frequently used by the CPU. It provides access to the CPU, so when the CPU requests data or programs the cache memory can transfer them to the CPU almost instantly. Cache memory usually sits between the CPU and RAM serves as a buffer between the two.

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10. External

External memory, also known as secondary memory, is memory not directly connected to the CPU that you can attach or remove as needed. There are many types of external memory that individuals use in their devices. Examples include external hard drives, flash drives, memory cards and compact discs (CDs). You can store data from a computer onto external memory, remove it from the device and connect it with another compatible device to transfer data.

11. Optical drive

Optical drive memory is an external memory that can both store and read data using light. The most common types are CDs, DVDs and Blu-ray discs. To access the contents on an optical drive, you place the disc inside the computer and the computer spins the disc. A laser beam inside the system scans it, receives the data on the optical drive and uploads it onto the computer. This type of memory can be useful because it's generally inexpensive, easily accessible and stores a lot of data.

12. Magnetic storage

Magnetic storage devices have a coating of magnetic material where it encodes data as an electric current. This type of memory uses magnetic fields to magnetize small sections of a metal spinning disk. Each section represents a "1" or a "0" and contains an extensive amount of data, often many terabytes. Users like this type of memory because it's affordable, durable and can store a lot of data. Common forms of magnetic storage devices are magnetic tape, hard disk drives and floppy disks.

13. Solid-state drives

Solid-state drives are a form of external memory made up of silicon microchips. They're similar to magnetic storage devices because you can remove them from the device you're storing or extracting data from, but solid-state drives are more modern. They're also faster because the memory keeps the binary data stored electrically in silicon chips known as cells. RAM uses a similar technique, but solid-state drives can keep memory stored even when you turn off a device because they use flash memory. Common types are the universal serial bus (USB) memory stick or USB flash drive.

14. Virtual

Virtual memory is another type of secondary memory in the form of a hard drive or solid-state drive that enables a computer to compensate for shortages of physical memory by transferring data from RAM to disk storage. When availability on RAM is running low, virtual memory moves data to a paging file, which is a portion of a hard disk used as an extension of RAM. This is a temporary process that disappears when RAM has more space available.

For example, if a user is on their device and using multiple applications at once, they may use a large portion of available RAM, which could slow down the device and its ability to efficiently operate the programs. The data the computer isn't using then gets transferred to virtual memory to provide more space for the RAM to run the applications at their full capacity.