Monday, October 15, 2007
10/15/2007 09:42:00 PM
hold crtl and f... this godlike command will enable you to find what you will need to find.. BEST of LUCK people!!!PART TWO of TEST1 WHAT IS A COMPUTER?
In very simple terms, a computer is a machine that can carry out various mathematical calculations, logical operations (like making decisions), text and information processing, according to a set of predefined instructions. A typical computer system consists of mainly two main components:
· Hardware
Includes all equipment and devices which are making up of electronic, electrical and mechanical components.
· Software
Consists of system, utilities and application software, which will instruct the hardware to perform the required task.
2 THE HARDWARE
There are basically 4 main units in a computer:
Ø The Central Processing Unit (CPU)
Ø The Memory Unit
Ø The Input Unit
Ø The Output Unit
2.1 The Central Processing Unit (CPU)
The CPU is the brain of the entire computer system. This is where all logical decisions and numerical computations are carried out. In a PC, the CPU is a single electronic chip with three main electronic sections:
Ø Arithmetic Logic Unit (ALU) - it does all computations and makes decision
Ø Control Unit - controls the operation of the computer system by sending electronic signals
Ø Internal Registers - the immediate memory storage within the CPU.
2.2 The Memory Unit
Memory holds data, instructions, and information. There are Memory Unit consists of 2 categories:
2.2.1 Primary Memory
There are 3 basic types of primary memory in the form of electronic chips: -
o Random Access Memory (RAM) chips
o Read Only Memory (ROM) chips
o Complementary metal-oxide semiconductor(CMOS)chips
· RAM (Random Access Memory) chips are called temporary or volatile storage because their contents are lost if power is disrupted.
o Cache memory or RAM cache is a high-speed holding area for frequently used data and information
o Virtual memory uses the hard disk or run large programs on systems with limited memory.
o Flash RAM or Flash memory is special type of RAM that does not lose its contents when power is disrupted.
· ROM (Read Only Memory) chips, also called firmware. This is permanent memory (i.e. non volatile) and stores programs and information needed by the computer to start up and do the basic routines required for the computer system to function effectively. The programs and data are burned-in to the ROM chip during manufacture.
· CMOS (Complementary metal-oxide semiconductor chips) provide flexibility and expandability to computer systems
2.2.2 Secondary Memory
Secondary storage devices can retain data and information after the computer system is turned off. They provide non-volatile storage. This is an auxiliary storage, which is used to store instructions or data that is not currently required.
· Floppy Disks
Are known as diskettes, disks, flexible disks, and floppies. Floppy disk drives (FDD) store data and programs by charging disk surface.
o Traditional Floppy Disk – 1.44 MB 3 ½ inch disk. 2DH indicates two-sided high density disk
o High Capacity Floppy Disk :
§ Zip disks – typical capacities are 100 MB, 250 MB, and 720 MB.
§ HiFD disks – typical capacities are 200 MB and 720 MB; HiFD drives can read traditional floopy disks.
§ SupperDisk Disks – typical capacities are 120 MB and 240 MB; SuperDisk drives can read traditional floppy disks.
· Hard Disks
Hard Disks are rigid metallic platters that provide much greater capacity
o Internal Hard Disk (Fixed disk) are located within system unit and typically identified as the C drive.
o Hard-Disk Cartridge is removable and capacity limited only by the number of cartridges. PC Card had disks are for notebooks.
· Optical Disks
Optical Disks use laser technology. Jewel boxes protect optical disks.
o Compact Discs (CDs) have typical capacity of 650 MB to 1 GB.
Four types:
· CD-ROM : read only, used to distribute databases. Reference, and software.
· CD-R : known as CD burners; used to create custom music CDs and to archive data.
· CD-RW: used for large multimedia presentation. Multiread CD-ROM can use CD-R and CD-RW disks.
· Picture and Photo CD: Picture CDs are single-session. Photo CDs are multisession.
o Digital Versatile Discs/ Digital video discs (DVD) have far greater
capacity then CDs
§ DVD-ROM(DVD Player identified as CD-DVD also read CD format)
§ DVD-R
§ DVD+RW (DVD+RAM a competing standard)
· Other types:
· Solid-state storage – no moving part.
· Flash memory cards are solid-state storage devices
· Key chain hard drives(key chain flash memory devices)
3. THE INPUT UNIT
This is a device where data or instructions that are used by a computer. Input devices translate words, images, and actions into a form a computer can process.
· Keyboard – traditional, flexible, ergonomic, wireless, and PDA.
· Pointing devices – mouse(mechanical, optical, cordless(wireless), trackball(roller ball), touch surface(touch pad),joysticks, touch screens, light pen.
· Scanners – optical scanners (flatbed and portable), bar code readers (scanners), Wand readers or platform scanners
· Character and mark recognition devices – magnetic-ink character recognition (MICR), optical-character recognition(OCR) and Optical-mark recognition (PMR, mark sensing)
· Image Capture Devices – Digital camera & digital video cameras (Webcams or Web cameras).
· Digitizing Devices – Graphic tablet & Digital notepads
· Audio Input Devices – Voice recognition systems (discrete-speed & continuous-speed), Musical Instrument Digital Interface(MIDI).
4. THE OUTPUT UNIT
This is a device whereby information provided by the computer can be kept or presented in a human readable form. Output devices translate processed text, graphics audio, and video into a form human can understand.
· Monitor (Display screens, screens) - Cathode ray tubes (CRTs), Flat-panel monitors (Liquid crystal display –LCD)
· Printers – Ink-jet printers, laser printers & Thermal printers, dot-matrix printers, plotters, photo printers and portable printers.
· Audio output devices – Speakers and headphones
. Examples are the CRT or monitor screen, plotter, printer, CD ROM Writer, etc.
5. INPUT AND OUTPUT DEVICES
Many devices combine input and output functions. Common types include:
· Fax machines –send and receive images via standard telephone lines.
· Multifunction devices (MDF) –typically combine the capabilities of a scanner, printer, fax and copy machine.
· Internet Telephone – Telephony (Internet telephony, IP Telephony) & Voice-over IP, VoIP)
· Terminals : Web terminal or Web appliance.
Disk drives, zip drives, floppy drives, magnetic tapes and magneto-optical drives functions as both input and output devices since these store programs and data output by the computer. The stored information can subsequently be retrieved or input back to the computer when required.
All I/O devices require an I/O Interface card to link the device to the CPU so that data communication can take place between the CPU and the devices. Many of these I/O interfaces are now built in as part of the mother board (main circuitry board), e.g.: parallel port for printer, COM port for mouse and modem, and USB port.
6. THE SOFTWARE
Software refers basically to the programs and instructions residing in the computer memory to get the computer to work. The hardware requires the software to provide step-by-step instructions to tell it what to do. The 2 categories of software are: systems software and applications software.
6.1 System programs
System programs are those special-purpose programs designed to meet the needs of the computer system. It consists of a variety of programs including:
· Operating Systems
An operating system is a set of routines that directs and manages the operation of the computer. It is software which acts as manager and traffic controller for the computer hardware. Examples of operating systems are Windows NT, Windows 2000, Windows XP, Windows 2003, Mac OS X , Linux, UNIX, etc.
· Utilities (service) programs
These are programs written to manage computer resources. E.g.: anti-virus program, scandisk, disk optimiser, etc.
· Device drivers
These are specialized programs to allow input and out devices to communicate with the rest of the computer system.
6.2 Applications Software
Programs that handle the processing for an application.
· General-purpose (basic applications) are widely used in nearly all career areas. Eg. Such as preparing the payroll, calculating the profit/loss of company or preparing a document are known as applications software. Some examples are: Microsoft Word, Excel, Lotus Notes, ACCPAC, SPSS, etc
· Special-purpose applications (specialized applications) focus on specific disciplines and occupations. These programs include graphics, audio and video, multimedia, Web authoring, and artificial intelligence programs
Reference:
SYSTEM UNIT (SYSTEM CABINET OR CHASSIS)
The System Unit contains most electronic components. Four basic types are:
· Desktop – placed horizontally or vertically; vertical units called tower models.
· Notebook – portable; often called laptops.
· Table PC – highly portable support stylus or pen input.
· Handheld – smallest; also known as personal digital assistant (PDA)
SYSTEM BOARD
The system board (main board or motherboard) connects all system components and a allows input and output devices to communicate with the system unit. It is a flat circuit board covered with electronic components:
· Sockets provide connection points for chips (silicon chips, semiconductors, integrated circuits). Chips mounted on carrier packages
· Slots provide connection points for specialized card or circuit boards.
· Bus lines provide pathways to support communication.
SYSTEM CLOCK
· System clock controls speed of operations. Clock speed (clock rate) is measured in gigahertz
(GHz)
EXPANSION SLOTS AND CARDS
Computers with closed architecture are not easily expanded. Open architecture computers typically have slots on their system boards to accept expansion card (plug-in board, controller cards, adapter card, or interface cards).
Eg. Video cards - also known as graphics cards, connect to the monitor
Modem cards – also known as internal modems, connect over a telephone line.
Network interface cards (NIC) – also known as network adapter cards, connect to a
Network.
BUS LINES
Also known as buses, provide data pathways that connect various system components. Bus width is the number of bits that can travel simultaneously.
PORTS
Ports are connecting sockets on the outside of the system unit.
· Standard Ports – Four standard ports are Serial, Parallel, USB (Universal series bus), and FireWire (HPSG or high performance serial bus).
· Cables – are used to connect external devices to the system unit via ports
POWER SUPPLY
Computer requires direct current (DC) to power their components. DC power supplied is by either converting alternating current (AC) from standard wall outlets or direct from batteries. Power supply units convert AC to DC; they are located within desktop computer’s system unit. AC adapters are used to power notebook computer and tablet PC’s and to recharge their batteries.