Types of Memory

A memory unit in a computer is a crucial component that stores data and instructions necessary for processing. It plays a vital role in a computer’s operation by providing storage for both temporary and long-term data. There are two primary types of memory units: Primary Memory (or RAM) and Secondary Memory (or storage devices).

Types of Memory Unit

1. Primary Memory (RAM)

Description: Primary Memory, often referred to as RAM (Random Access Memory), is a type of volatile memory that temporarily stores data and program instructions while the computer is running. It provides fast access to data that the CPU actively uses for processing.

Characteristics: It is volatile, meaning data is lost when the computer is powered off. RAM is typically faster than secondary memory and comes in different capacities (e.g., 4GB, 8GB, 16GB).

Types of Primary Memory

• RAM (Random Access Memory)
  • Static RAM (SRAM)
  • Dynamic Random Access Memory (DRAM)
• ROM (Read Only Memory)
  • PROM (Programmable Read Only Memory)
  • EPROM (Erasable Programmable Read Only Memory)
  • EEPROM (Electrically Erasable Programmable Read Only Memory)

(i). RAM (Random Access Memory) 

The Word “RAM” stands for “random access memory” or may also refer to shortterm memory. It’s called “random” because you can read store data randomly at any time and from any physical location. It is a temporal storage memory. RAM is volatile that only retains all the data as long as the computer 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 (SRAM): Static RAM is the form of RAM and made with flip-flops 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.

(ii). ROM (Read Only Memory)

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 RAM, 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.

2. Secondary Memory (Storage Devices)

• Description: Secondary Memory refers to non-volatile storage devices used for long-term data storage. Unlike RAM, data stored in secondary memory persists even when the computer is powered off. Common examples include hard disk drives (HDDs), solid-state drives (SSDs), optical discs (like DVDs), and USB flash drives.
• Characteristics: Secondary memory provides large storage capacity and is slower in terms of data access compared to RAM. It is used for storing the operating system, software applications, documents, and other files.

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Difference between Primary Memory and Secondary Memory

Here are the key differences between Primary Memory (RAM) and Secondary Memory (Storage Devices):

1. Volatility:

• Primary Memory (RAM): Volatile; data is lost when the computer is powered off.
• Secondary Memory (Storage Devices): Non-volatile; data persists even when the computer is powered off.

2. Data Access Speed:

• Primary Memory (RAM): Faster data access, suitable for active data processing.
• Secondary Memory (Storage Devices): Slower data access, primarily used for long-term storage.

3. Storage Capacity:

• Primary Memory (RAM): Limited capacity, typically smaller in size (e.g., 4GB to 32GB).
• Secondary Memory (Storage Devices): Larger capacity, ranging from gigabytes (GB) to terabytes (TB).

4. Purpose:

• Primary Memory (RAM): Used to store data and program instructions actively used by the CPU during processing.
• Secondary Memory (Storage Devices): Used for long-term storage of the operating system, software applications, user files, and data.

5. Data Retention:

• Primary Memory (RAM):Data is retained only while the computer is powered on.
• Secondary Memory (Storage Devices): Data is retained even when the computer is powered off.

In summary, Primary Memory (RAM) is fast, volatile, and suitable for temporary data storage during active computer operation. Secondary Memory (Storage Devices) provides non-volatile, high-capacity storage for long-term data retention and is slower in terms of data access. Both types of memory play critical roles in a computer’s functionality.