Different types of Internal & External Memory.pptx

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1. DIFFERENT TYPES OF INTERNAL & EXTERNAL MEMORY Name:Mohitkumar Naik Roll No:36

2. What is Internal Memory ? Computer memory can be classified either as internal memory or as external memory. The internal memory is the one that is directly accessible to the processor via system bus and the external memory is accessed via input-output channels of the computer . The internal memories of the computer are made up of semiconductor material usually silicon. This memory is costlier and is usually small in size as compared to the external memory.

3. Types Of Computer Memory

4. Random Access Memory (RAM ) The RAM memory is the fastest but is a volatile memory. That means to retain its content the RAM memory has to be provided with a constant power supply. Once the power supply to this memory chip is switched off this memory chip loses all its content. It is easy to read data from and write data into the RAM memory. The data is read or written into the RAM memory using the electric signals. Further, the RAM memory has two other forms DRAM and SRAM.

5. DRAM & SRAM Dynamic Random Access Memory ( DRAM) It stores information as long as the power is supplied Capacitors are used to store data in DRAM . To store information for a longer time, contents of the capacitor need to be refreshed periodically . DRAM provides slow access speeds. These are cheaper Static Random Access Memory (SRAM) It stores information as long as the power is supplied.  Transistors are used to store information in SRAM . Capacitors are not used hence no refreshing is required . These are expensive

6. Read-Only Memory ( ROM) Read-only memory (ROM) is a non-volatile memory which means the memory cells of this memory chip do not require a power supply to retain its bit value. As this is a read-only memory the bit values of this memory can only be read and not be written or modified . Like RAM the ROM also has some other forms such as programmable ROM, erasable programmable ROM, electrically erasable programmable ROM, and flash memory .

7. Programmable Read-Memory(PROM ) A Memory chip on which data can be written only once. The difference between a PROM & ROM(Read-only memory)is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process.

8. Erasable Programmable Read Memory(EPROM) Erasable programmable read only memory, can be read and written using electrical signals. Well before a write operation is performed the memory content of this memory chip are erased to retain its initial state by exposing the memory chip to the ultraviolet rays .

9. Electrically Erasable Programmable ROM (EEPROM) The  electrically erasable programmable ROM  (EEPROM) is the ROM memory that can be erased selectively and written multiple times. Unlike the EPROM where the entire data gets erased when exposed to the ultraviolet rays. The EEPROM is a little complex when compared to the EPROM as it requires different electrical voltage to erase the data.

10. Cache Memory The cache memory is a volatile memory that loses its memory content once the power supply to the memory unit is interrupted. The cache memory keeps the copies of the recently accessed information from the main memory . T he cache memory stores the frequently use information. The cache memory is faster and costlier and smaller than RAM memory .

11. What Is External Memory? External memory  can also be known as secondary memory or backing store. It is used to store a huge amount of data because it has a huge capacity. At present, it can measure the data in hundreds of megabytes or even in gigabytes. The important property of external memory is that whenever the computer switches off, then stored information will not be lost. The external memory can be categorized into four parts: Magnetic Disk Optical Disk Optical Memory Magnetic Tape

12. Magnetic Disk A disk is a type of circular platter constructed by a nonmagnetic material, which is known as a  substrate.  It is covered with a magnetic coating used to hold the information . The substrate is traditionally constructed by aluminium or aluminium alloy material . But recently, another material has been introduced, which is known as  glass substrates.   It has the ability to increase disk reliability by improving the uniformity of a magnetic film surface.It is used to reduce the errors of read-write by doing a significant reduction in overall surface defects. It has better stiffness, which will help to reduce disk dynamics. It has the great ability that it can withstand against shock and damage.

13. Optical Disk The optical disk storage system includes a rotating disk coated with a diminished layer of metal that facilitates a reflective surface and a laser beam, which is used as a read/write head for recording information onto the disk. Unlike magnetic disk, the optical layer consists of a single long track in the form of a spiral shape. The spiral shape of the track produces the optical disk applicable for reading huge blocks of sequential information onto it, including music.

14. Optical Memory Optical memory  is an electronic storage medium that uses a laser beam to store and retrieve the data. If we classify the memory system then optical memory comes under the external memory in the computer system. Optical memory can be classified into many types . Examples of optical memories are: Compact Disk (CD), Digital Versatile Disk ( DVD), and Bluray Disk (BD).

15. Magnetic Tape Magnetic tape is a type of physical storage media for different kinds of data. It is considered an analog solution, in contrast to more recent types of storage media, such as solid state disk (SSD) drives . Reading and writing techniques in the tape system is the same as the disk system. Magnetic tape has been a major vehicle for audio and binary data storage for several decades, and is still part of data storage for some systems.

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