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Computer systems.

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Introduction

COMPUTER SYSTEMS The computer system consists of the actual computer it self. Additional devices are called peripherals. A typical computer system is like any other desktop computer, these are known as microcomputers. Desktop computers are used for commercial applications, these process large amounts of data Output Device- a device where data moves out of the computer system, so that the user can view it. Input Device- a device used by the user to input data to the computer system. Storage Device- device such as tape/disk, which stores data. Microcomputers, which can be operated using re-chargeable batteries, is called a lap-top computer. The CPU is known as the brain of the computer, all the instructions are carried out here. The control unit is a part of the CPU, which controls the timing and executions of individual instructions. ALU (arithmetic and logic unit) where calculations are carried and logical comparisons are made. IAS (immediate access store) also known as the primary storage. This holds programs and data that are in use. RAM (random access memory) volatile, and lost when the computer is switched off. ROM (read only memory) non-volatile, data isn't lost when the computer is switched off, and is used to store system software. ...read more.

Middle

This method is also used for gases and electricity bills as well the national lottery. Advantages) fast and accurate compared to manual methods. OCR (Optical Character Recognition) works in the same ways as OMR, light is reflected on to the sheet, the pattern of light is then compared with characters in the reader and the characters are recognised. Disadvantages) slow and very inaccurate, however newer machines accept a wider range fonts. MICR (Magnetic Ink Character Recognition) This method is used in banking. The numbers are printed on the check using special ink so reading is very fast. Additional information such as account number, cheque number and bank sort code is printed on the cheque as well. Advantages) Writing over or alteration of the ink will not affect the reading. High security Disadvantages) expensive and therefore isn't used in other applications. BARCODE READER- the amount of light reflected by the dark and light lines represents different characters. The barcode has 2 half and therefore it can be read in any direction. In the library there are barcodes on the books and the cards, which means loans and returns can be entered in to the computer system. It's possible for a barcode to be misread. ...read more.

Conclusion

Floppy disks also store data and are made up of magnetisable material; the material is normally covered in card or plastic. The most common type of disks is 3.5" floppies. These hold 1.44MB of data. The main application is keep copies and back-up copies of files. Optical disks (CD-ROMs) these work in the same way. A light bean is reflected on to the disk, the reflection determines whether it's a 1 or 0 binary digit. A low-density beam is used to read the data, while a stronger density beam is used to write the data. Once data has been written, it cannot be changed or altered, which makes it unfit for some applications. Optical disks can hold a lot of memory. Software distributors use 1 optical disk compared to many floppies. Advantages, 1. CD-ROMs are reliable therefore there is no problem with media. 2. Software can be read from the CD and doesn't have to be installed. 3. More space, therefore more support files can be supplied. 4. Can hold a lot memory, 700MB Disadvantages, 1. CDs can only be written over once 2. CDs which are badly scratched cant be read 3. CDs are more expensive than floppies We can use CD-R to write data on to optical disks, however writing is slower than a hard disk. ...read more.

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