Different Types of Computer Memory

A group of 4 bits is called a nibble. A byte is also known as an Octet.

Primary Storage (memory), also known as main storage and it is the area in a computer in which data is stored for quick access by the computer's processor. The terms random access memory (RAM) and memory are often as synonyms for primary or main storage. Primary storage is volatile and can be contrasted with non-volatile secondary storage, also known as auxiliary storage.

Cache memory is a smaller, faster memory which stores copies of the data from frequently used main memory locations. A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average time to access data from the main memory.

Secondary memory is where programs and data are kept on a long-term basis. Common secondary storage devices are the hard disk and optical disks. The hard disk has enormous storage capacity compared to main memory. The hard disk is usually contained inside the case of a computer.

Read-only memory (ROM) is a storage medium used in computers and other electronic devices. Data stored in ROM can only be modified slowly or with difficulty, or not at all.

ROM is non-volatile and the contents are retained even after the power is switched off.

It only allows reading.

The types of ROM include PROM, EPROM and EEPROM.

PROM - (programmable read-only memory) is a memory chip on which data can be written only once.

The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called a PROM programmer or PROM burner.

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

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

Random Access Memory (RAM), allows the computer to store data for immediate manipulation and to keep track of what is currently being processed.

RAM is referred to as volatile memory and is lost when the power is turned off.

It also known as read/write memory as information can be read from and written onto it.

The two main types of RAM are Static RAM and Dynamic RAM.

SRAM retains data as long as power is provided to the memory chip and need not be refreshed periodically. It is often used as CPU Cache memory. SRAM stands for Static Random Access Memory.

The data on DRAM continues to move in and out of the memory as long as power is available and must be continually refreshed to maintain the data. DRAM stands for Dynamic Random Access Memory.

Virtual memory is memory on the hard disk that the CPU uses as an extended RAM.