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Basic Computer Organization


Posted Date: 01-Jun-2009  Last Updated:   Category: Computer & Technology    
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Basic Computer Organization



In Computer System, different parts of a computer are organized in such a way that, it helps to perform various operations to complete the given specific task. A computer is a sort of electric brain, which capable to solve mathematical problems with in movements or produce desired information or a controlling order. More technically. A computer is a high-speed electronic data processing machine. Widely computer use to perform arithmetic calculations. However, now-a-days computer is using for many other purposes. There are five basic operations. They are

1. Inputting
2. Outputting
3. Control unit
4. Storage unit
5. Processing

1. INPUT: This operation is used to feed the information in the computer. The standard devices are keyboard, Mouse-a pointing device, and card redirect. The input devices must accept the data from the outside world and the computer to process it must accept the same data. The data or information feuded through the keyboard are stored in the storage device.

2. OUTPUT: This operation is used to display the feeded data or the processed data. Some standard output devices are monitor or screen, printer, etc. These output devices must accept the data, which was processed by the processor. The processing is done binary format and it must be converted to understandable form.

3. CONTROL UNIT: This unit is used to control all the devices, which is helpful for processing. It controls the inflow and outflow of data. It works like a traffic cop, which controls the movement of data from memory to processing unit. We can also say it as central nervous system of the computer. Because it controls and co-ordinates all the devices. It must accept the value returned by the ALU and also by the memory.

4. STORAGE UNIT: Storage unit is to store any kind of information. Whatever the data inserted or feeded through keyboard is first stored in the memory for further processing. It must store the intermediate results and also final result. The memory in the storage unit is divided in the form of cells. Each and every cell has its address.
Memory is divided in two types.

A.)RAM: Random Access Memory. It is a type of memory, which access randomly. All the values are not stored sequentially. This type of memory is also called Read/Write memory. That means the values are stored as well as it can be retrieved from the memory. There are two types of RAM.

(I) Static RAM
(ii) Dynamic RAM


(I) STATIC RAM: Values are stored throughout the process. It consumes more power.
(ii) Dynamic RAM : Data stored in this memory must be refreshed in every milliseconds. Otherwise the values are erased off. It consumes less power and it is it's advantage.

B.) ROM: Read Only Memory. The content in this memory is mainly used for reading purpose. The program cannot be altered, added, or modified by the user.
PROM : Programmable Read Only Memory. This is similar to ROM.
EPROM: Erasable Programmable Read Only Memory. This type of ROM is used to make changes in the ROM contents. The programs must be deleted everything and new program must be added. Some portion of the program cannot be altered. Whole program must be deleted and fresh or new Program must be loaded in the ROM chip.

EEPROM : Electrically Erasable Programmable Read Only Memory: ROM chip of this type used to erased a small portion of the program with the help of high voltage.

Processing: Processing is done in Arithmetic Logical Unit (ALU). Any kind of data stored in the memory flow through control unit to ALU for processing are again stores the result in the memory, which flows to control Unit. The combination of control unit and the ALU is called Processor.


SECONDARY STORAGE DEVICES:


The values, programs or the contents in file are basically stored in primary devices called hard disk or local disk. Some other storage devices called secondary storage devices used to store the values. They are also used for transportation of data.

1. Punched Paper cards: This type of storing data is used in the form of punched holes. The paper card is in the form of rolls and it width is of one inch. The values are stored in row wise. The punched holes in the form of rows are called channels. So, each row in the card represents a character.

2. Floppy Disks: This type of storage devices are commonly used now a days. The disk is made of plastic cover coated with magnetic oxide, and it is covered with hard plastic cover. Disk is divided in the form of tracks and in sector wise. The data is stored in the tracks in sector wise.

3. Winchester Disk: Winchester disk is closed in a hard cover and it is not recommended to open. A special type of lubricant is used to reduce the friction when the head pointer moves to read the data.

4. Optical Readers: This type of input devices is used to read the special characters, marks, printed characters, etc. This is a special device which the marks with the reflection of light.

a) OMR : Optical Mark Reader. This device is used to read the marks, bars, or any other special character or symbols.
For example, to read the rate of the products, a bar code reader is used to read the bars available on the product's cover.
OMR sheets are used to dark the marks wherever necessary so that the mark reader reads the dark objects as it's input.

b) OCR : Optical character Reader. This is used to read only hand written characters, printed characters. The hand written character must be in standard width, height, etc. There shouldn't be any loops as we write in running letters. The printed characters must be in standard font and size.

Output devices:



1. Visual Display Unit (VDU): This is the most common device used with microcomputers. It is having the technology of CRT, which is also used in television. CRT - Cathode Ray Tube. It displays the character on the screen instead of on papers. The printed text is also called softcopy. The screen varies in different sizes. Normally the screen has 24 lines and 80 characters.

2. Plotters:
Plotters are used to produce designs and graphs. There are basically two types : a) Drum plotter b) Flatbed plotters.
a) Drum Plotters: It is having a drum in which the paper is fixed and it is moved to and fro which makes it in vertical motions.
The pens are clamped in the holder with different set of colors and they are moved in horizontal directions. When the both move simultaneously the graphs or design are produced on the paper.

b) Flatbed Plotters: In this type of plotters the paper is not fixed and set of colored pens are in motion. These are controlled by the computer.
Plotters are normally slow because it is marked up lots of mechanism as compared to the speed of computers.

3) Printers: Printers are of two types. They are impact and non-impact printers.
a) Impact Printers: This type of printers normally leaves the impression of the characters on the paper.
b) Non-Impact Printers: Printers of this type are quiet and fast and they don't leave any impression.

a) Impact printers: These are of two types, character printers and line printers.
Character printers: In this type of printers one character is printed at a time. For example, a typewriter, which prints one character at a time.
Some examples of character printers are:
1) Letter-Quality printer: This is of impact printers having a set of font wheels also known as daisy wheel. This wheel is set to rotate at a high speed. And whenever the desired character is required, a hammer which is behind the paper strikes the paper. 10-50 characters are printed in a second.

2)Dot-Matrix Printers: These printers print each character as a pattern of dots. The print head had matrix of tiny needles. The print quality is inferior to letter-quality printers but faster than it. These printers are less expensive as compared to daisy wheel. These printers can print any shape characters as described by the printer.

3)Ink-Jet Printers: These are non-impact printers which prints the characters by spraying small drops of ink onto paper. It produces high quality output because the characters are formed by dozens of tiny ink dots. They are quiet and form any shape of characters.

Line Printers: Line printers are impact printers used with large computer system to produce huge output. They are fast printers.
Drum Printers and Chain Printers are commonly used.

1) Drum Printer: Drum printers are consists of a solid, cylindrical drum that has raised characters in bands of its surface. There are many bands and it rotates at high speed. When the desired character appears, the hammer strikes the paper along with the ribbon which is behind it. One revolution is required to print one line.

2) Chain Printers: They use rapidly moving chains called print chain. As the print chain rotates, there is a print hammer located behind the paper and when it founds the desired character it strikes on the paper along with the inked ribbon.

Page Printers: Page printers are non-impact printers, which can produce documents with a high speed. For example, xerography, lasers and other technologies. These techniques called electro photographic techniques. Printers of this type are extremely fast and cost effective.

Computer Software:


It is a set of programs written in a language in order to control the applications. Operating system is also a collection of software. Software contains the collection of commands to be performed by the computer. Operating system acts as a resource allocater, which allocates resources to authorize users.


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