Computer memory and basics of computers understanding
1. Computer Memory
By: Victor Barman
UGC NET(LS)
Department of Computer and System Sciences
Visva-Bharati, Santinektan
2. Computer memory is a fundamental component of a computing system, serving as the
storage space for data and instructions needed for processing. It is essential for the efficient
functioning of any computer.
Types of Memory
Computer memory can be broadly categorized into two types: Primary Memory and Secondary Memory.
1.Primary Memory
1. Definition: Also known as main memory, this type of memory is directly accessible by the CPU. It is volatile,
meaning it loses its contents when the power is turned off.
2. Examples:
1. RAM (Random Access Memory): Temporary storage used by the CPU to store data and instructions that are
actively being used or processed.
2. ROM (Read-Only Memory): Non-volatile memory that holds essential instructions for the computer's startup
process. The data in ROM is permanent and cannot be easily modified.
2.Secondary Memory
1. Definition: Also known as auxiliary or external memory, this type of memory is used for long-term storage of
data. It is non-volatile, meaning it retains its data even when the power is off.
2. Examples:
1. Hard Drives (HDDs): Magnetic storage devices used for storing large amounts of data.
2. Solid State Drives (SSDs): Faster, more reliable storage devices that use flash memory.
3. CDs/DVDs: Optical storage media used for data distribution and backup.
4. USB Flash Drives: Portable storage devices that use flash memory.
3. A memory cell is the fundamental building block of a computer's memory, responsible for
storing individual bits of information, either a 0 or a 1. Multiple memory cells are
organized together to form more substantial memory units, like bytes, kilobytes, and so
on. Byte Addressable
Memory
4. Find the total number of cells in 64kb memory chip.
Q.
Size of each cell = 8
Number of bytes in 64kb = (2^6)*(2^10)
Therefore, the total number of cells = 2^16 cells
6. Semiconductor Memory :
A type of electronic memory known as semiconductor memory stores digital data by making use of
semiconductor materials, most commonly silicon. Data is stored in binary format in this memory, with "1s"
and "0s" representing electrical charges.
Types of semi conductor memory
•Random Access Memory(RAM)
•Read-Only Memory(ROM)
•Programmable Read-Only Memory(PROM )
•Erasable Programmable Read-Only Memory(EPROM )
RAM (Random Access Memory): Volatile memory that stores data temporarily while the computer is
running.
•Types:
• DRAM (Dynamic RAM): Needs to be refreshed periodically to retain data. Basically used in
primary storage, it consists of capacitor.
• SRAM (Static RAM): Does not need refreshing, faster but more expensive. Used in cache, it
consists of transistors, flip-flops.
•Use: Provides temporary storage for data and instructions that the CPU needs to access quickly.
8. ROM (Read-Only Memory): Non-volatile memory that permanently stores data.
•Types:
• Mask ROM: Programmed during the manufacturing process.
• Firmware ROM: Contains essential instructions for booting the computer (BIOS).
•Use: Stores firmware and system software that do not change frequently.
PROM (Programmable Read-Only Memory): A type of ROM that can be programmed once after
manufacturing.
•Programming: Requires a special device called a PROM programmer.
•Use: Used in applications where the data does not need to be changed after it is programmed.
Example: Older gaming consoles and certain calculators.
EPROM (Erasable Programmable Read-Only Memory): A type of ROM that can be erased and
reprogrammed.
•Erasing Method: Uses UV light to erase the data.
•Reprogramming: Can be reprogrammed multiple times using a special device.
•Use: Ideal for applications where updates to the stored data are occasionally required.
• Example: Older personal computers with EPROM-based BIOS chips.
10. Secondary Storage Devices
Secondary storage devices are used to store data permanently.
The most common types of secondary storage devices are:
1. Hard Disk Drives (HDDs): Mechanical storage devices that use spinning disks (platters)
coated with magnetic material to read and write data.
•Characteristics:
• High storage capacity (several terabytes).
• Slower access speed compared to SSDs.
• Cost-effective for large amounts of storage.
•Use: Ideal for general data storage, operating systems, and applications.
11. 2. Solid State Drives (SSDs): Storage devices that use flash memory to store data, with no
moving parts.
•Characteristics:
• Faster access and data transfer speeds.
• More durable and reliable due to the lack of mechanical parts.
• Higher cost per gigabyte compared to HDDs.
•Use: Preferred for operating systems, applications, and high-performance computing tasks.
3. Optical Storage Devices: Use lasers to read and write data on optical discs such as CDs,
DVDs, and Blu-ray discs.
•Characteristics:
• Medium storage capacity (up to 128 GB for Blu-ray).
• Slower access speed compared to SSDs and HDDs.
• Suitable for data distribution and media playback.
•Use: Ideal for backups, media distribution, and archiving.
12. 4. USB Flash Drives: Portable storage devices that use flash memory and connect to computers
via USB ports.
•Characteristics:
• Portable and easy to use.
• Moderate storage capacity (up to 2 TB).
• Faster access speed compared to optical storage but typically slower than SSDs.
•Use: Convenient for transferring files between devices and temporary storage.
5. Memory Cards : Small, portable storage devices used in cameras, smartphones, and other
portable electronics.
•Types:
• SD (Secure Digital) Cards: Commonly used in cameras and portable devices.
• MicroSD Cards: Smaller version of SD cards, used in smartphones and tablets.
•Characteristics:
• Small size and lightweight.
• Moderate to high storage capacity (up to 1 TB or more).
• Fast access speed.
•Use: Used in portable electronics for storage of photos, videos, and other data.
