Computer Hardware PDF

Computer Hardware By Dr. Safynaz AbdEl-Fattah Computer Science Benisuef University  What is computer ? A computer is a programmable, electronic device that accepts data, performs operations on that data, and stores the data. It follows instructions, called programs, whic...

Computer Hardware By Dr. Safynaz AbdEl-Fattah Computer Science Benisuef University  What is computer ? A computer is a programmable, electronic device that accepts data, performs operations on that data, and stores the data. It follows instructions, called programs, which determine the tasks the computer will perform.  Computer Components A computer has five Basic Operations: Input: Entering data into the computer Processing: Performing operations on the data Output: Presenting the results Storage: Saving data, programs for future use Communications: Sending or receiving data  Hardware components The hardware components can be classified into four main units, namely: 1. Input Unit 2. Output Unit 3. Central Processing Unit 4. Memory Unit These units are interconnected by minute electrical wires to permit communication between them. This allows the computer to function as a system.  Hardware components 1. Input Unit: A computer uses input devices to accept the data and program. Input devices are the tools that allow communication between the user and the computer. 2. Output Unit: Output devices have an interface between the computer and the user. These devices take machine coded output results from the processor and convert them into a form that can be used by human beings.  3. Central Processing Unit CPU is the brain of any computer system. It takes all major decisions, makes all sorts of calculations and directs different parts of the computer function by activating and controlling the operation. It consists of arithmetic and logic units, control unit and internal memory (registers).  Central Processing Unit CPU consists of: 1. The control unit of the CPU coordinates the action of the entire system. Control unit (CU) controls all the hardware operations, ie, those of input units, output units, memory unit and the processor. 2. The arithmetic and logic units (ALU) in computers are capable of performing addition, subtraction, division and multiplication as well as some logical operations. 3. Registers and Internal Cache Memory: Store data and instructions needed by the CPU. 4. Bus Interface Unit: It allows the core to communicate with other CPU components  Central Processing Unit Multi-core processors allow computers to work on more than one task at a time. A Dual-core CPU contains the processing components (cores) of two separate processors on a single CPU. Quad-core CPU contains four cores. Personal computer CPU often made by Intel or AMD. Media tablets and mobile phones use processors made by other companies such as ARM. The GPU (graphics processing unit): A GPU takes care of the processing needed to display images (including still images, animations) on the screen.  Central Processing Unit Processing Speed: is the number of instructions a CPU can process per second. Rated in megahertz (MHz) or gigahertz (GHz). For example, a gigahertz, the most common form of processor speed, means that one billion cycles can be completed per second. Word Size: The amount of data that a CPU can manipulate at one time; typically 32 or 64 bits. Cache Memory: Special group of very fast memory chips located on or close to the CPU. Level 1 is fastest, then Level 2, then Level 3. More cache memory typically means faster processing.  4. Memory Unit In the main memory, the computer stores the program and data that are currently being used. The main memory holds data and program only temporarily. A program must be resident in main memory to be executed. There are different types of memory. They are Random Access Memory (RAM), Read Only Memory (ROM), There is a need for storage devices to provide backup storage (secondary storage devices). Secondary storage devices can hold more storage than main memory and is much less expensive.  Random Access Memory – RAM This is really the main store and is the place where the program gets stored. When the CPU runs a program, it fetches the program instructions from the RAM and carries them out. If the CPU needs to store the results of the calculations it can store them in RAM. When we switch off a computer, whatever is stored in the RAM gets erased. It is a volatile (‫ )سريعة الزوال‬form of memory.  Read Only Memory - ROM In ROM, the information is burnt (pre-recorded) into the ROM chip at manufacturing time. Once data has been written into a ROM chip, it cannot be erased or updated but you can read it. When we switch off the computer, the contents of the ROM are not erased but remain stored permanently. ROM is a non-volatile memory. ROM stores critical programs such as the program that boots the computer. BIOS (Basic input output system) is stored in ROM. BIOS runs as soon as the computer is switched on. It checks that the hardware is functioning correctly, then loads the computer operating system. Case  Case The main case of a computer – Houses the processing hardware for a computer it contains storage devices, the power supply, and cooling fans it, houses processor, memory, interfaces to connect to peripheral devices (printers, etc), and other components. With a desktop computer, usually looks like a rectangular box  Case A power supply is used to convert AC power into a lower voltage DC power required by internal components. Cooling fans: Fans used on most personal computers to help cool the CPU and system unit Heat is an ongoing problem for CPU and computer manufacturers: Can damage components Cooler chips run faster  Motherboard The motherboard is the backbone of the computer. It is a printed circuit board (PCB) that contains buses that interconnect electronic components. These components may be soldered (‫ )ملحوم‬directly to the motherboard, or added using sockets, expansion slots, and ports. It is located inside the computer case and is where most of the parts and computer peripherals connect. Ports and Connectors  Buses A Bus is an electronic path within a computer over which data travel. It is located within the CPU and etched onto the motherboard. Expansion Bus: Connects the CPU to peripheral (typically input and output) devices. Memory Bus: Connects CPU directly to RAM Universal Serial Bus (USB): Allows 127 different devices to connect to a computer via a single USB port.  Input devices Any data or instructions used by a computer An input device is used to feed data into a computer. Some hardware input devices include: 1. Keyboards: Keyboard consists of a set of typewriter like keys that enable you to enter data into a computer. 2. Mouse Mouse is an input device that controls the movement of the cursor on the display screen.  Input devices 3. Scanner: Scanner is an input device that allows information such as an image or text to be input into a computer. 4. Bar Code Reader The barcode readers are used in places like supermarket, bookshops, etc. A bar code is a pattern printed in lines of different thickness. The bar-code reader scans the information on the barcodes and transmits to the computer for further processing..  Input devices 5. Digital Camera The digital camera is an input device mainly used to capture images. The digital camera takes a still photograph, stores it and sends it as digital input to the computer. 6. Touch Sensitive Screen It is a pointing device that enables the user to interact with the computer by touching the screen.  Input devices 7. Light Pen  A light pen is a pointing device shaped like a pen and is connected to a monitor.  The tip of the light pen contains a light sensitive element which, when placed against the screen, detects the light from the screen enabling the computer to identify the location of the pen on the screen.  Light pens have the advantage of ‘drawing’ directly onto the screen. 8. Magnetic Reader Magnetic reader is an input device which reads a magnetic strip on a card.  Input devices 9. Smart Cards This input device stores data in a microprocessor embedded in the card. This allows information, which can be updated, to be stored on the card. These data can be read and given as input to the computer for further processing. 10. Microphone Microphone serves as a voice input device. It captures the voice data and input to the computer.  Output devices Output is anything that comes out of a computer. An output device is capable of presenting information from a computer. There are many output devices attached with the computers. But the monitors and printers are commonly used output devices. 1. Monitors It provides a visual display of data. Monitors are connected with the computer and are similar in appearance to a television set.  Output devices 2. Speakers The computer can also produce voice output(audio data). Speaker serves as a voice output device. 3. Plotters plotters are also used to produce graphical output. 4. Printers Printer is an output device that prints text or images on paper or Other media (like transparencies).  Storage Devices Secondary storage is also called backup storage. Secondary storage can be used to transmit data to another computer either immediately or a latter time. This provides a mechanism for storing a large amount of data for a long period of time. Some of the commonly used storage devices are hard disks, magnetic tapes, floppy disks and CD-ROM. The average time required to reach a storage location and obtain its contents is called its access time.  Storage Devices Data storage devices can be classified according to the media on which the data is stored: Magnetic – like hard disk drive, tape drive and Floppy disk drive Optical – like CD and DVD Solid state – like solid state drive  Hard Disk Hard disk is a magnetic disk on which you can store computer data. The hard disk is a direct-access storage medium. This means you can store and retrieve data randomly. Disk storage systems are essentially based on magnetic properties. The magnetic disk consists of high speed rotating surfaces coated with a magnetic recording medium. The rotating surface of the disk is a round flat plate. When writing data, a write head magnetizes the particles on the disk surface as either north or south poles. When reading data, a read head converts the magnetic polarizations on the disk surface to a sequence of pulses.  Hard Disk The read and write heads are generally combined into a single head unit. There may be more than one read/write head. Data is arranged as a series of concentric rings. Each ring (called a track) is subdivided into a number of sectors, each sector holding a specific number of data elements (bytes or characters). The smallest unit that can be written to or read from the disk is a sector. The storage capacity of the disk is determined as (number of tracks * number of sectors * bytes per sector * number of read/write heads)  Magnetic Tape A recording medium consisting of a thin tape with a coating of a fine magnetic strip, used for recording digital data. The tape itself is a strip of plastic coated with a magnetic recording medium. Bits are recorded as magnetic spots on the tape along several tracks. Usually, seven or nine bits are recorded simultaneously to form a character together with a parity bit. Read /write heads are mounted one in each track so that data can be recorded and read as a sequence of characters.  Floppy Disk The floppy drive uses a thin circular disk for data storage. It is a soft magnetic disk. It is a thin magnetic-coated disk contained in a flexible or semi-rigid protective jacket. The disk rotates at 360rpm. A read/write head makes physical contact with the disk surface. Data is recorded as a series of tracks subdivided into sectors.  Optical Disk Optical disks are a storage medium from which data is read and to which it is written by lasers. The optical disk is a random access storage medium; information can be easily read from any point on the disk. CD-ROM stands for Compact Disk - Read Only Memory. It is now possible to have CD ROMs where tracks of information can be written onto them by the user. These are called read/write CD-ROMs and these are becoming a popular and cheap method for storage.  Solid-state drives Solid-state drives (SSD) a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage. It is also sometimes called a solid-state device or a solid-state disk. This makes SSDs much faster than magnetic HDDs. SSDs have no moving parts, make no noise, are more energy efficient, and produce less heat than HDDs.