Subject: Teacher Training
A basic computer consists of 4 components:
An input device is a hardware or peripheral device used to send data to a computer. An input device allows users to communicate and feed instructions and data to computers for processing, display, storage and/or transmission.
Examples of input devices include keyboards whicha allow users to input data and pointing devices and game controllers such as mouse and joysticks.
Input also may come from other computers via input/output (I/O) devices like network adapters and Bluetooth ports.
An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) which converts the electronically generated information into human-readable form.
Examples of output devices include:
CPU (pronounced as separate letters) is the abbreviation for central processing unit. Sometimes referred to simply as the central processor, but more commonly called processor, the CPU is the brains of the computer where most calculations take place.
The computer memory is a temporary storage area. It holds the data and instructions that the Central Processing Unit (CPU) needs. Before a program can be run, the program is loaded from some storage medium into the memory. This allows the CPU direct access to the program.
Based on their read write capability and their storage capability, computer memory can be one the following types.
ROM is the computer memory on which data is prerecorded. Once data has been written onto a ROM chip, it cannot be removed and can only be read. Unlike main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile. For e.g., ROM- BIOS (Basic Input and Output System). The function of BIOS is to load files from CD or Hard Disk into primary memory (ROM).
Here data and instruction are programmed during manufacturing process and if it malfunctions we have to replace it with new one, e.g. ROM- BIOS
Programmable read-only memory (PROM) is read-only memory ( ROM ) that can be modified once by a user. PROM is a way of allowing a user to tailor a microcode program using a special machine called a PROM programmer .
EPROM is reprogrammable ROM. We can erase the content written in EPROM and replace it with new one. The programs are erased using UV rays.
EEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., device configuration.
Like EEPROM, flash memory can be erased by electrical signal and erasing process is faster than EEPROM. It is possible to erase a particular block of data or instructions instead of entire data bits in flash memory.
It stores information in the form of charge; there is probability of leakage of charge, so it needs to be regularly refreshed. It can store more information than static RAM (S-RAM). Capacitor is the device that's used to store the charge, e.g. DDR, DDR2
Unlike D- RAM, S- RAM stores information in the form of voltage. It is much faster than D-RAM and it is fully able to keep pace with modern processor. Here transistors are used instead of capacitor so refreshing is not required . The S-RAM chips are physically larger but stores less bits per area.
Auxiliary memory is used as permanent storage of data. The data and instructions are supplied to primary memory from auxiliary memory. They are used for storing system program, large data files and other back up information. This is called non-volatile memory and can store tremendous amount of data, e.g. Optical storage, magnetic storage.
CD- ROM (Compact Disk Read Only Memory):
It is read only optical storage medium and are capable of holding about 700mb of data. Accessing data from CD- ROM is very fast than floppy disk but considerably slower than modern hard disk. The disk is made up of polycarbonate wafer, 120 mm in diameter and 1.2 mm thick with a hole of 15mm in the middle. The wafer base is coated with metallic film usually an aluminum alloy. The aluminum film is covered by a plastics poly carbonate coating that protects the underlying the data. In CD- ROM, data and instructions are represented in form of land and pits. The lights are reflects from the land and diffused from pits.
CD- RW (Compact Disk- Read/ Write Memory): CD-RW (Compact Disc-ReWritable) is a digital optical disc storage format. A CD-RW disc is a compact disc that can be written, read arbitrarily many times, erased and written again. The technology was introduced in 1997. In CD- RW, the change of state i.e. the formation of land and pit is not permanent. Laser is used to heat the active material in CD-RW to liquid state to create required land and pits to save the data.
Digital Versatile Disk (DVD): It is the improved version of CD-ROM, i.e. it can store multiple times more data in the same sized disk. This is possible due to the reduction in the size of land and pit. So bits are packed more closely on DVD then CD- ROM. They are available as DVD-ROM, DVD-RW.
Blue Ray Disk: It is the latest optical storage medium more sophisticated than DVD. It was developed mainly to store High Definition Video (HD Video), Video games and other data that are more than 2.5 GB. The name Blu-Ray is derived from blue laser used to read/write the disk. It was developed by Blu-Ray Disk Association and MIT.
The magnetic devices use principle of electromagnetism for storing and receiving data. The surface of magnetic devices is coated with magnetic material, the lightening process done by using READ/ WRITE ARM. The Surface of storage device produces small current to flow which is sensed by Read/write arm and is sent o main memory, e.g. Hard Disk, Magnetic tape, Magnetic Drum, etc.
Hard Disk Drives: HDDs were introduced in 1956 as data storage for an IBM. It contains rigid, disk shaped platters, constructed from Aluminum or glass. The physical construction of hard disk consists of spinning disks with heads that moves over the disks and stores data in tracks and sector. The heads read and write the data in concentric circles called tracks which are divided into segments called sectors. They have multiple spinning disks called platters which are stacked on top of each other. The actuators move the read and write head at required position in platters.
Floppy disk are made from Mylar (A plastic materials) coated with magnetic material(Iron Oxide). It is soft magnetic disk and is very thin piece of flexible plastics, also called diskette. It is kept within a plastic jacket and metallic shutter that protects the media access hole. Its storage capacity was 1.4MB. The various sizes of 3.5"Â, and 8" ÂÂÂare found.
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