Chapter 2 computer system


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Chapter 2 computer system

  1. 1.  A computer system is defined ascombination of components designed toprocess data and store files. Acomputer system consists of four majorhardware components; inputdevices, output devices, processor andstorage devices. A computer systemrequires hardware, software and a userto fully function.
  2. 2. input• Input is any data or instructions that we enter into the computer system for processing. Thereare four types of input: which are text, graphic, audio and video. Example of input devices arekeyboard, light pen, joystick, microphone, mouse, video & digital camera.process• The processing unit controls all activities within the system. The CPU is an example of aprocessor. It has the same important as the brain to human being.Storage• Storage is a location which data, instruction and information are held for future use. Itis the physical material that keeps keeps data, instruction and information. There aretwo types of storage. They are the primary storage and secondary storage. The exampleof storage devices are hardisk, Floppy Disk, diskette, RAM, CD ROM and DVD ROM.output• Output is data that has been processed into a useful form, called information. Thereare four types of output, which are texts, graphics, audio and video. Example of outputdevices are monitor, printer, speaker and plotter.
  3. 3. input•Users input data or instructioninto the computer system to beprocess. Input could be eithertext, graphic, audio or video.Input devices are used by users toinput data. Input devices are anyelectronic device connected to acomputer and produces inputsignals.process•Data or instruction being inputinto the computer system is thenprocessed by the CPU whichcontrols all activities within thesystem. The results of theprocessed data are then sent to anoutput device as usable data.•A CPU interprets the and carriesout the instructions by processingdata and controlling the rest ofthe computer’s components.•A CPU consists of twosubcomponents; the Control Unit(CU) and the Arithmetic LogicUnit (ALU). CU’s main function isto direct the CPU to process databy extracting instructions frommemory and decodes and executesthem. The CU manages a four-stepbasic operation which is called amachine cycle. The steps areFetching, Decoding, Executing &Storingstorage•Computer storage is important tohelp users store programs and datato be used at a later time.•It is also useful to keep currentdata while being processed by theprocessor until the information issaved in a storage media such as ahard disk or a diskette. Computerstorage also stores instructionsfrom a computer program. Thereare two type of computer storage;primary storage and secondarystorage.
  4. 4. BinarydigitBitByteCharacterCharactercodes
  5. 5. BINARY DIGIT Computers recognize only two discrete states: on and off. These states can berepresented by two digits, 0 and 1. Each 0 or 1 is called a bit in the binary system. Bit is the smallest unit of data a computer can process. Bit is a short for binary digit.The binary system has a base of 2 with the two digits (0 and 1). Combinations of 0s and 1srepresent larger numbers.BIT A bit is the smallest unit of data that the computer can process. Bit is a short for binarydigit. A bit is represented by the numbers 1 and 0. These numbers represent the binarysystem. They correspond to the states of on and off, true and false, or yes and no. All digital data use the binary system to process the information. This informationinclude letters, digits or special character.BYTE Byte is a unit of information built from bits. One byte is equals to 8 bits. Eight bitsthat are grouped together as a unit. A byte provides enough differentcombinations of 0s and 1s to represent 256 individual characters. One byte represents a single character such as the number 3, letter b or a $symbol. Bits and bytes are the basis for representing all meaningful information andprograms on computers.
  6. 6. CHARACTER 8 bits = 1 byte One byte represents one character such as A, 7, 9 and +.Eight bits that are groupedtogether as a unit. A byte provides enough different combinations of 0s and 1s torepresent 256 individual characters. For example, the capital letter F is represented by the binary code 01000110 that canbe understood by the computer system. Eight bits grouped together as a unit arecalled a byte. A byte represents a single character in the computer.CHARACTER CODES There are three character codes to represent characters which are ASCII, EBCDICand Unicode. Each byte contains eight bits. A byte provides enough differentcombination of 0s and 1s to represent 256 characters. The combinations of 0s and 1s are defined by patterns. These patterns are calledcoding scheme. The 256-character capability of ASCII and EBCDIC is too small tohandle the characters that are used by other languages such as Arabic, Japanese andChinese. The Unicode coding scheme is designed to solve this problem. It uses two bytes (16bits) to represent one character. Unicode will have more than 65,000 differentcharacters. This can cover all the world’s languages.
  7. 7. ASCII code ASCII pronounced as "ask-key" stands for the AmericanStandard Code for Information Interchange and wasproposed by ASA (American Standard Association) in 963and was finalised in 1968.ASCII is a standard of 7-bit codeused to represent characters, which includeletters, numbers and punctuation marks. 7 bits allow the computer to encode a total of 128characters for the numbers 0-9, uppercase and lowercaseletters A-Z and a few punctuation symbols. However this 128bit code only suitable for english language speaking users. IBM and Apple expanded the amount of space reserved forthe character codes to 8-bits, equivalent to 1 byte.
  8. 8. Functionsof ASCIIcodesASCII was established toachieve compatibilitybetween various types ofdata processing equipmentmaking it possible for thecomponents tocommunicate with eachother successfully.ASCII enablesmanufacturers to producecomponents that areassured to operatecorrectly in a computer.ASCII makes it possiblefor humans to interactwith a computer. It alsoenables users to purchasecomponents that arecompatible with theircomputer configurations
  9. 9. When you press akey, for example theletter D on yourkeyboard, theelectronic signal issent to the CPU forthe computer toprocess and store inmemory.Every character isconverted to itscorrespondingbinary form.The computer theprocesses theletter as abyte., whichactually a series ofon and off ofelectrical states.When thecomputer isfinishedprocessing thebyte, the softwareinstalled in thesystem convertthe byte backwhich is thendisplayed in thescreen.In thisexample, the letterD is converted to01000100.
  10. 10. • You can enter data by pressing the keys onthe keyboardText• A digital camera allows you to takepictures and store the photographedimages digitallyGraphic• Input the speech, music and sound effectsentered into the computerAudio• Input of motion images captured into thecomputer by special input devices.Video
  11. 11. ComponentsofmotherboardCentralProcessingUnit (CPU)ExpansionSlotExpansionCardsRAM SlotPortsandConnectors
  12. 12. Information anddocument are stored incomputer storage sothat it can be retrievedwhenever they areneeded later on.Computer storage isthe holding of data inan electromagneticform for access by acomputer processor.Storage
  13. 13. Stores instructions from a computer programsHelp users store programs and data to be used at alater timeFunction of Computer Storage
  14. 14. Definition of operating system Set of programs that schedule tasks,allowcates storage and presents adefault interface to the user betweenapplications.Function of the operating system are : Starting a computer Providing a user interface Managing data and programs Managing memory Configuring devices