1 PERSONAL COMPUTERS

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1 PERSONAL COMPUTERS 1

2 2 Personal computer a desktop computer a laptop a tablet PC or a handheld PC

3 Software applications for personal computers include word processing spreadsheets databases web browsers and clients games special-purpose software 3 Modern personal computers often have high-speed or dial-up connections to the Internet, allowing access to the World Wide Web and a wide range of other resources. Personal computers can be connected to a local area network (LAN) either by a cable or wirelessly.

4 4 Basic diagram of a computer Information processing cycle a set of steps a computer follows to receive & process the data (according to instructions), display the info & store the results Central processing unit (CPU) Memory unit Input device Arithmetic logic unit (ALU) Output device Control unit

5 5 Unit Central processing unit (CPU) / processor: a) Memory Unit (also known as the primary storage or main memory) Function the part of the computer that carries out the instructions of a computer program the unit that reads and performs programme instructions the part known as the brain of the computer stores data, programme instructions, internal results and final output temporarily before it is sent to an appropriate output device consists of thousands of cells called storage locations. These cells activate with off-on or binary digits(0,1) mechanism a character either a letter or numerical digit is stored as a string of (0,1) binary digits ( BITS). These bits are used to store instructions and data by their combinations.

6 6 Unit Function b) Arithmetic Logic Unit The unit where all arithmetic operations (addition, subtraction etc.) and logical functions such as true or false, male or female are performed. Once data are fed into the main memory from input devices, they are held and transferred as needed to ALU where processing takes place. No process occurs in primary storage. Intermediate generated results in ALU are temporarily placed in memory until needed at later time. Data may move from primary memory to ALU and back again to storage many times before the process is finalised.

7 7 Unit Input device Output device Function reads information from input media and enters to the computer in a coded form decodes information and presents it to the user c) Control Unit acts as a central nervous system and ensures that the information is stored correctly and the programme instructions are followed in proper sequence as well as the data are selected from the memory as necessary. coordinates all the input and output devices of a system.

8 8 Removable Storage and / or Disk Drives - All disks need a drive to get information off - or read - and put information on the disk - or write. Each drive is designed for a specific type of discwhether it is a CD, DVD, hard disk or floppy. Often the term disk and drive are used to describe the same thing but the disk is the storage device which contains computer files - or software - and the drive is the mechanism that runs the disk. Digital flash drives use memory cards to store information - there are no moving parts. Digital cameras also use Flash memory cards to store information, in this case photographs. Hand held devices use digital drives, many also use removable or built in memory cards. A disc refers to optical media, such as an audio CD, CD-ROM, DVD-ROM, DVD-RAM, or DVD-Video disc. A diskrefers to magnetic media, such as a floppy disk, the disk in acomputer's hard drive, an external hard drive.

9 9 Keyboard - is used to type information into the computer or input information. The most common for Latin based languages is the QWERTY layout (named for the first 6 keys). The standard keyboard has 101 keys. Notebooks have embedded keys accessible by special keys or by pressing key combinations (CTRL or Command and P for example). Hand held devices have various and different keyboard configurations and touch screens. Some of the keys have a special use. They are referred to as command keys.

10 Mouse 10 Touch pads Printers: dot matrix, ink jet, laser printers Scanners Monitors - The monitor shows information on the screen - outputting information. When the computer needs more information it will display a message on the screen, usually through a dialog box. The resolution of the monitor determines the sharpness of the screen. Most desktop computers use a monitor with a cathode tube or liquid crystal display (LCD).

11 11 Cables connect internal components to the Motherboard (mainboard, system board) - a board with series of electronic path ways and connections allowing the CPU to communicate with the other components of the computer such as the CPU and memory, and provides connectors for other peripherals. It is the hub, the most important component in the PC. It contains the processor, memory chips, interfaces, sockets

12 Cards - are components added to computers to increase their capability. Sound cards allow computers to produce sound like music and voice. The older sound cards were 8 bit then 16 bit then 32 bit. Graphic cards allow computers to produce colour. The first colour cards were 2 bit which produced 4 colours [CGA]. Next came 4 bit allowing for 16 [EGA and VGA ] colours. Then came 16 bit allowing for 1064 colours and then 24 bit which allows for almost 17 million colours and now 32 bit and higher allow monitors to display almost a billion separate colours. Video cards allow computers to display video and animation. Some video cards allow computers to display television as well as capture frames from video. A video card with a digital video camera allows computers users to produce live video. A high speed connection is required for effective video transmission. Network cards allow computers to connect together to communicate with each other. Network cards have connections for cable, thin wire or wireless networks. 12

13 13 Memory Memory or storage capacity is one of the important components of a computer. Any data that are to be processed by the CPU must be placed into the main memory (sometimes known as primary storage). Any storage unit of a computer system is classified on the basis of the following criteria: 1. Access time: This is the time required to locate and retrieve stored data from the storage unit in response to programmeinstructions. 2. Storage capacity: It is the amount of data that can be stored in the storage unit. 3. Cost per bit of storage.

14 14 Memory - one of the easiest pieces of hardware to add to a computer. It is common to confuse chip memory with disk storage. An example of the difference between memory and storage would be the difference between a table where the actual work is done (memory) and a filing cabinet where the finished product is stored (disk). Random Access Memory (RAM) - the memory that the computer uses to temporarily store the information as it is being processed. It is a volatile storage device. The more information being processed the more RAM the computer needs. Read-Only Memory (ROM) - is used to hold a small, special piece of software the boot up programme (also known as the BIOS basic input output system). ROM is non-volatile storage the data is never lost even if the power is switched off.

15 15 Advantages of computers 1. High speed: Computers have the ability to perform routine tasks at a greater speed than human beings. They can perform millions of calculations in seconds. 2. Accuracy: Computers are used to perform tasks in a way that ensures accuracy. 3. Storage: Computers can store large amount of information. Any item of data or any instruction stored in the memory can be retrieved by the computer at lightning speeds. 4. Automation: Computers can be instructed to perform complex tasks automatically (which increases the productivity). 5. Diligence: Computers can perform the same task repeatedly & with the same accuracy without getting tired. 6. Versatility: Computers are flexible to perform both simple and complex tasks. 7. Cost effectiveness: Computers reduce the amount of paper work and human effort, thereby reducing costs.

16 16 Limitations of computers: 1. Computers need clear & complete instructions to perform a task accurately. 2. If the instructions are not clear & complete, the computer will not produce the required result. 3. Computers cannot think. 4. Computers cannot learn by experience.