Memory
Computer memory refers to the storage device which stores data, instructions required during the processing of data, and also the output results. Computer use two types of storage memories:
- Primary memory:
Primary memories are also referred as main memory are volatile in nature and comparatively faster but have less storage capacity than secondary memory. - Secondary memories:
Secondary memories are also referred as external memory or auxiliary memory refers to permanent storage locations such as hard drives and solid state drives.
Types of memory:
Cache memory:
Cache memory pronounced as cash is an extremely high speed, small and expensive semiconductor memory placed in between CPU and main memory. It is used to hold those parts of data and program which are most frequently used by the CPU. It has also two parts:
- Internal cache:
Cache located inside of the CPU is internally cache. Level 1 cache is an internal cache is an internal cache which is integrated onto the chip itself. - External cache:
Cache located outside of the CPU is external cache. It is also referred as L2 and in the size it is bigger and in the speed it is slower than the internal cache.
Primary memory
Primary memory also referred as main memory or internal memory which stores data, programs, instructions, and intermediate result of processing temporary.
Characteristics of primary memory:
- It is volatile in nature except ROM.
- Its storage capacity is less than the secondary memory.
- It is semiconductor memory used to store data temporarily.
- It is directly accessible to the CPU.
- It is faster in operation than secondary memory.
Types of primary memory
Random Access Memory (RAM):
RAM consists of one or more memory modules that temporarily store data while a computer is running. Each time you start up your computer, the operating system must be loaded from secondary memory into the primary memory or RAM. Types of RAM are:
Static RAM (SRAM):
SRAM is a type of RAM made with flip-flops which retains in latch as long as the computer is powered, unlike DRAM which requires periodic refreshing. It is used as cache memory.
Dynamic RAM (DRAM):
DRAM is a type of RAM which retains each of data in capacitors for short period even though the computer is powered. It needs periodic refreshment to maintain data in it. It is used as main memory.
Different between SRAM and DRAM
| SRAM | DRAM |
| It stands for Static Random Access Memory. | It stands for Dynamic Random Access Memory. |
| Memory type which uses flip-flop to store each bit of data. | Memory type which stores each bit of data in a separate capacitor within an integrated circuit. |
| It is much faster compared to DRAM. | It is slower than SRAM. |
| It doesn’t need periodic refreshment to maintain the information. | It needs periodic refreshment to maintain the information. |
| It is expensive than DRAM. | It is comparatively cheaper. |
| It has low packaging density. | It has packaging density. |
| Its storage capacity is low. | Its storage capacity is high. |
Read Only Memory (ROM)
ROM is the permanent memory which stores important control programs and systems software to perform a variety of functions, such as booting up or starting up programs. It is also called non-volatile memory. Its types are:
PROM
PROM is a type of ROM where that data can be written only once by a user. Once the data is written in it, we can rewrite the data on it.
EPROM
EPROM is a type of ROM which the programmed data can be erased. The programmable read-only memory can be programmed to write data with high voltage and the data remains until it is exposed to ultraviolet light for lasting up to 10 minutes or longer.
EEPROM
EEPROM is a type of ROM which is similar in a way that the data are erasable, but the ways to program and erase are done by exposing it to an electrical charge, so on transparent window is needed.
Different between RAM and ROM
| RAM | ROM |
| It stands for Random Access Memory. | It stands for Read Only Memory. |
| It is volatile in nature. | It is non-volatile in nature. |
| It allows both read and write operations. | It allows only read operation. |
| Writing data to a RAM chip is faster process. | Writing data to a ROM chip is slower process. |
| Physical size of RAM chip is larger than ROM chip. | Physical size of ROM chip is smaller than RAM chip. |
| The cost of RAM is expensive. | The price of ROM is comparatively low. |
| Types of RAM are SRAM and DRAM. | Types of ROM are PROM, EPROM and EEPROM. |
Secondary Memory
Secondary memories are also referred as external memory or auxiliary memory refers to permanent storage locations such as hard drives and solid state drives. It may also refers to removable storage media, such as external hard drives, DVDs, USB flash drives, etc.
Characteristics of primary memory
- It is used for storing data and programs permanently.
- It is non-volatile in nature and larger in storage capacity.
- It is not directly accessed by CPU.
- The read/write operation is comparatively slower than primary memory.
- It can be used for transferring data and programs between devices.
Types of secondary memory
Magnetic storage
It uses property of magnet for storing data. It contains data storing surface coated by magnetic oxide. Magnetic memory allows data to be accessed randomly as well as sequentially. It is categorized into two groups:
Magnetic tape
Magnetic tape is a plastic tape with magnetic coating which is used for storing data such as text, audio, and video. It contains thin plastic ribbon where the data storing side is coated with magnetic oxide.
Magnetic disk
Magnetic disks are the most popular direct access secondary storage device. It is a storage device that uses a magnetization process to write, rewrite and access data. It is covered with a magnetic coating and stores data in the form of tracks, spots and sectors. Some of the popular magnetic disks are hard disks and floppy disks:
Hard disk
A hard disk is a data storage device that uses magnetic storage to store and retrieve digital information. Inside a hard disk drive, there are one or more platters coated with a magnetic material. These platters spin rapidly while a read/write head moves across them, allowing data to be read from or written to specific locations on the platters.
Floppy disk
A floppy disk, often simply referred to as a floppy, is a magnetic storage medium that was commonly used for data storage and transfer in the late 20th century and early 21st century. Floppy disks were popular from the 1970s through the 1990s before being largely phased out by other storage technologies such as CD-ROMs, USB flash drives, and cloud storage. Floppy disks are characterized by their flexible, thin magnetic storage medium encased in a square or rectangular plastic shell. The most common sizes for floppy disks were 5.25 inches and 3.5 inches, with the latter becoming more prevalent in the later years due to its higher storage capacity and more durable design.
SSD (Solid State Drive)
SSD is a data storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory. Unlike traditional Hard Disk Drives which store data on spinning disks, SSDs have no moving parts, which makes them faster, more durable, and less prone to mechanical failure.
Optical Storage
Optical storage refers to the storage of data using optical media, which utilizes laser light to read and write data onto a disc. Optical storage devices use laser technology to read and write data on specially designed discs, such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and Blu-ray discs. Here are some key points about optical storage:
CD (Compact Disc):
CDs were one of the earliest forms of optical storage. They typically store up to 700 MB of data and are commonly used for storing music, software, and other digital content.
CD-R:
It is a blank CD where data can be stored once only.
CD-ROM:
It is read only disk which means the data comes pre-recorded and cannot be erased and written.
CD-RW:
It is erasable disk which allows user to record and erase data so that disk can be used multiple times.
DVD (Digital Versatile Disc):
DVDs have a larger storage capacity compared to CDs, typically ranging from 4.7 GB (single-layer) to 8.5 GB (dual-layer). They are commonly used for storing movies, software, and larger amounts of data.
Blu-ray Disc:
Blu-ray discs have the highest storage capacity among optical media, typically ranging from 25 GB (single-layer) to 100 GB (quad-layer). They are commonly used for high-definition movies, as well as for storing large amounts of data, such as backups and archives.
Flash memory:
Flash memory is a type of non-volatile computer storage that can be electrically erased and reprogrammed. It is used for storage in devices such as USB drives, memory cards, SSDs, and various types of embedded systems. Flash memory works by trapping electrically charged electrons in a floating gate transistor, which alters the transistor’s conductivity and stores binary data.
Some of the advantages of flash memory are listed below:
- It is less expensive than other semiconductor memory.
- Unlike RAM, they are non-volatile in nature.
- Flash drives consume less power and produce less heat compared to HDDs.
Pen drives:
A pen drive, also known as a USB flash drive, thumb drive, or jump drive, is a portable data storage device that uses flash memory to store and transfer digital data. It typically consists of a small, rectangular plastic or metal casing with a USB connector at one end.
Memory card:
A memory card is a small, portable storage device used primarily in electronic devices such as digital cameras, smartphones, tablets, portable gaming consoles, and various other devices to store and transfer digital data. Memory cards are often used to expand the storage capacity of devices or to facilitate data transfer between devices.