Primary Storage

It's also known as main storage or memory and this is the main area in a computer in which data is stored for quick access by the computer's processor. Examples of Primary storage are RAM and ROM that store programs. These memories are limited in capacity and manufactured by using integrated circuits (IC) or semiconductor device.

Fig 1.1 Primary Storage

Primary storage is fast(It allows very fast access to data) and expensive as compared to secondary storage.

Random Access Memory(RAM)
 It’s called “random” because you can read stored data randomly, at any time and from any physical location. It is a temporal storage memory. RAM is volatile, in the sense that it only retains all the data on it as long as the computer is powered. It is the fastest type of memory. RAM stores the currently processed data from the CPU and sends them to the graphics unit.

There are generally two broad subcategories of RAM:

• Static RAM: Static RAM is the form of RAM and made with flipflops and used for primary storage are volatile. It retains data in latch as long as the computer powered. SRAM is more expensive and consumes more power than DRAM. It used as Cache Memory in a computer system. As technically, SRAM uses more transistors as compared to DRAM. It is faster compared to DRAM due to the latching arrangement, and they use 6 transistors per data bit as compared to DRAM, which uses one transistor per bit.

• Dynamic Random Access Memory (DRAM): It is another form of RAM used as Main Memory, its retains information in Capacitors for a short period (a few milliseconds) even though the computer powered. The Data is Refreshed Periodically to maintain in it. The DRAM is cheaper, but it can store much more information. Moreover, it is also slower and consumes less power than SRAM.

Read Only Memory(ROM)
ROM is the long-term internal memory. ROM is “Non-Volatile Memory” that retains data without the flow of electricity. ROM is an essential chip with permanently written data or programs. It is similar to the RAM that is accessed by the CPU. ROM comes with pre-written by the computer manufacturer to hold the instructions for booting-up the computer.

There is generally Three broad type of ROM:

• PROM(Programmable Read Only Memory): PROM stands for programmable ROM. It can be programmed only be done once and read many. Unlike ROM, PROMs retain their contents without the flow of electricity. PROM is also nonvolatile memory. The significant difference between a ROM and a PROM is that a ROM comes with pre-written by the computer manufacturer whereas PROM manufactured as blank memory. PROM can be programmed by PROM burner and by blowing internal fuses permanently.

• EPROM (Erasable Programmable Read Only Memory): EPROM is pronounced "ee-prom". This memory type retains its contents until it exposed to intense ultraviolet light that clears its contents, making it possible to reprogram the memory.

• EEPROM (Electrically Erasable Programmable Read Only Memory): EEPROM can be burned (programmed) and erased by first electrical waves in a millisecond. A single byte of a data or the entire contents of device can be erased. To write or erase this memory type, you need a device called a PROM burner.

Fig 1.2 The Categories of Primary Storage

Sources

• Thakur, Dinesh. “Dinesh Thakur.” Computer Notes, ecomputernotes.com/fundamental/input-output-and-memory/what-is-primary-storage.
• Thakur, Dinesh. “Dinesh Thakur.” Computer Notes, ecomputernotes.com/fundamental/input-output-and-memory/primary-memory.