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CATEGORIES OF COMPUTER HARDWARE NAME: SHAIBU UNEKWU-OJO ABDULLAHI GST 115: INTRODUCTION TO ICT LEVEL: 100L DEPT: MECHATRONICS ENGINEERING INTRODUCTION A computer system consists of two broad components, known as Hardware and Software. The hardware refers to the physical units or achiness or functional units which make up the computer configuration. The hardware can be divided into these categories: Central processing unit Main memory Secondary\auxiliary storage Input devices Output devices Connectivity hardware CPU – CENTRAL PROCESSING UNIT The Central Processing Unit s also called Processor. This is the brain or heart of the computer equipment. The CPU carries out the calculations for the program and controls the other components of the system. It does the function by organizing circuits into two main units, called Arithmetic Logic Unit and Control Unit. MICROPROCESSOR A microprocessor (processor) is an integrated circuit designed to process instructions. It is the most important and usually the most expensive components of a computer. It can be more accurately described as a CPU on a chip because it contains-on a single chip-circuitry that performs essentially the same task as the central processing unit (CPU) of a classic mainframe computer. For example: intel® Pentium® Extreme Edition Dual Core with HT Technology #.20GH z, 800mHz FSB, 2 MB Cache. Microprocessors performance is affected by several factors; including clock speed, bus speed, word size, cache size, instruction set and processing techniques. Clock speed: 3.20GHz indicates the speed of microprocessor clock- a timing device that sets the pace for executing instruction. A cycle is the smallest unit of time in a microprocessor’s universe. A cycle is the smallest unit of time in a microprocessor’s universe. A specification such as 3.2GHz means that the microprocessor’s clock operates at a speed of 3.2 billion cycles per second. A computer with 3.2GHz will be faster than 1.5GHz or 933MHz processor. Front side Bus: FSB refers to the term that refers to the circuitry that transports data to and from the microprocessor. A fast side bus moves data quickly and allows the processor to work at full capacity. It ranges from 200MHz to 1250MHz. Word size: refers to the number of bits that a microprocessor can manipulate at one time. Word size is based on the size of register in ALU and the capacity of circuits that lead to those registers. For example a processor with a 32 bit word size has 32-bit register, processor. (Will have 64bits). Cache: it is a temporary storage area in the memory. It is a special highspeed memory that allows a microprocessor to access data more rapidly than from memory located elsewhere on the system board. Instruction set: this is the collection of pre-programmed activities such as addition, subtraction, comparison, division and multiplication. We have complex instruction set computer with complex instructions each requiring several clock for execution. Also there is reduced instruction set computer (RISC), it performs most instruction faster than a CISC processor. Processing technique; some processor executes instruction serially; that is one instruction at a time, this is known as serial processing. The processor must complete all steps in the instruction cycle before it begins to execute the next instruction. Pipelining: a processor can begin executing an instruction before it completes the previous instruction. Parallel Processing: multiple instructions are executed at the same time. Dual Core Processor: it’s a computer having a single chip containing the circuitry for two microprocessor. It is faster than single core processors. The ALU contains circuits that do Arithmetic and Perform Logical Operations. The Control Unit contains circuits that analysed and execute instructions. The Arithmetic Logic Unit The ALU contains arithmetic circuits that can subtract multiply and divide two numbers. More complex operations such as finding the square root of a number are done by sequence of their basic operations. To perform a calculation or logical operation, number is transferred from primary storage to storage registers in the ALU. These numbers are sent to the appropriate arithmetic or logic circuit. The results are sent back to the storage registers. The results are transferred from the storage registers to primary storage. The microprocessor’s Control Unit fetches each instruction, Data is loaded into the ALU’s register and finally the Control Unit gives the ALU the green light to begin processing. Instruction Cycle refers to the process in which a computer executes a single instruction. Some parts of the instruction cycle are performed by the microprocessor’s Control Unit, other parts of the cycle are performed by the ALU. The instruction thata computer is supposed to process for a particular program. Are held in memory. When the program begins, the memory address of the first instruction is placed in a part of the microprocessor’s control unit called an Instruction Pointer. The control unit can then fetch the onstruction by copying data from that address into its instruction register. From there, the control unit can interpret the instruction, gather the specified data or tell the ALU to begin processing. The Control Unit fetches instructions interprets them, fetches data and tells the ALU which processing operations to perform. ALU uses register to hold data that are ready to be processed. When it gets the go-ahead signal from the Control Unit, the ALU processes the data and places the result in an accumulator from the accumulator, the data can be sent to memory or used for further processing. The Control Unit The control Unit controls the whole computer system by performing the following functions: Directs and Coordinates all operation called for by the program Activates the appropriate circuits necessary for inputs and output devices. Causes the entire computer system to operate in an automatic manner. The control unit contains a temporary storage location called an instruction register for storing the instruction being executed. It also contains circuits called the instruction decoder – which analyse the instruction register and cause it to be executed. The control unit executes each instruction by following the same basic sequence of steps: The next instruction in the program is retrieved for primary storage and stored in the instruction register The instruction is sent to the instruction decoder where it is analysed. The decoder sends signals to the ALU, primary storage, I/O devices, and secondary storage that cause the actions required by the instructions to be performed. PRIMARY STORAGE/ MAIN MEMORY Primary storage is also called internal storage or memory. It is used to store programs and data currently being processed by CPU. Primary storage circuits like light bulbs need electricity to stay on. If the power to the computer is turned off, all the circuits will turn off and all data in primary storage will be lost. When computer is turned back on the data will not reappear. The data is lost forever. Because of this characteristic primary storage is called volatile storage. This type of primary storage is called RANDOM ACCESS MEMORY or RAM. RAM is the main type of primary storage used with computers and it is volatile. ROM Several computers have another type of primary storage called ROM – Read Only Memory. ROM is non-volatile storage. This means that when the power to the computer is turned off, the content of the ROM is not lost. ROM can store preset programs that are always put by computer manufactures. When you turn on a PC, you will usually see a reference on BIOS (Basic Input output System). This is part of the ROM chip containing all the programs needed to control the keyboard, monitor, disk drive, etc. There are different types of ROM, including PROM, EPROM and EEPROM. PROM – Programmable Read Only Memory – In this type of ROM, data or program can be stored once in PROM but never changed. EPROM – Erasable Programmable Read Only Memory – In this type of ROM, data or program can be erased by removing the device and exposed it to ultraviolet light. EEPROM – Electrically Erasable Programmable Read Only Memory – data or program can be completely erased using a special device and new programs or new data can be stored in it. The Use of Primary Storage (RAM) Main Memory has several uses: Input area – where the data is stored when it is read into CPU, awaiting processing. Operating system – controls the operation of the computer. Working storage – where calculations are performed and data is stored temporarily. Output area where the information is stored prior to output. Both the input and output areas are buffer. Application program area – where the user program is held. SECONDARY STORAGE Secondary Storage is an optional attachment, which is cable –connected to the CPU. Secondary is non-volatile. Any data or programs stored in secondary storage stays there, even with the computer power turned off, unless someone purposely erases them. Secondary storage is a permanent from of storage. They are cheaper forms of storage that can store a lot of information until they are needed. They can also be called offline storage media. There are various data storage devices which are encompassed into three main categories 1. The magnetic media 2. The optical media 3. Semi conducting media THE MAGNETIC MEDIA: Examples include the floppy disk, hard disk and magnetic tape. For years, the magnetic technology has dominated the mass storage arena. The most common example in use today is the magnetic disk, in which thin spinning disk with magnetic coating is used to hold data. Read/write concentric heads are placed above and/or below the disk so that the disks spins, each head traverses a circle, called a track, around the disk’s upper or lower surface. By repositioning the read/write head, different concentric tracks can be accessed. FLOPPY DISK: This has a square shape. The protective square case houses a round piece of flexible plastic disk with a magnetic coating. It is portable and has a very small size of 1.44MB. The reading and writing speed is very slow and it is not durable. They are not common these days because of the associated disadvantages. Though they are new types of floppy disk with bigger capacity and better durability but they require special drive to drive them and thus they are not popular. Examples include Zip Disk (up to 750MB) and super disk (120MB) HARD DISK: Hard disk is a very huge type of memory and it is one of the factors that determine how powerful a computer system is. It contains a set of circular plates made of metal with a magnetic coating. All the plates are sealed within a hard disk drive together with a read/write head. It rotates at a very high speed. When data is to be read from a hard disk, the computer gives the disk address and the hard disk will go to the specific location to read the data. THE MAGNTIC TAPE: This is a magnetically coated strip of plastic on which data are stored. Large amount of data can be stored on it. It is very cheap. It requires a tape drive to read and write data on a tape. It is a slow storage device mainly used for long term storage and backup OPTICAL MEDIA: These are storage media that hold content in digital form and such content can be written and read using laser technology. These storage media include CD and DVD variations. COMPACT DISK: CD is a round plastic disc with metal coating. It implores laser technology for storing and accessing data. It can be further classified into: CD-ROM Group, CDR (CD recordable), CD-RW (CD rewriteable).these disks are 12 centimetres in diameter and consist of reflective materials covered with a clear protective coating. Information is recorded on them by creating variations in their reflective surfaces. This information can be retrieved by means of a laser beam that monitors irregularities on the reflective surface on the CD as it spins. B.DIGITAL VERSATILE DISK: this is an advanced storage media. It has a diameter and thickness similar to the CD. It can also be further classified into: DVD ROM, DVDR, DVD-RW, Magneto-Optical Disks. SEMI-CONDUCTING MATERIAL: these are often called flash memories. They use semi-conductor clips to store data. They are silent in operation and they are used in some portable devices such as digital cameras, PDA and MP3. Examples include: Microdrive (MD), Secure Digital card (SD card), Compact flash card (CF card) and Smart Media card (SM card). A semiconductor chip may contain millions of tiny transistors or capacitors. INPUT DEVICES Input devices are devices that allow users to enter data and command into the computer system. Some of these devices are explained below: 1. MAGNETIC INK CHARACTER RECOGNITION (MICR): The concept behind MICR is that human readable characters reprinted on documents in an ink that is magnetisable and are also designed in a special type of font. The ink contains ferrous oxide, and so by magnetising it when read into MICR reader/sorter, the characters become recognisable. 2. MOUSE: A mouse is a handheld device, which allows you to control your computer without having to type instructions from the keyboard. It helps you to move around your computer screen, select any object and activate commands. The computer mouse shape resembles an actual mouse. It has rubber ball embedded at its lower sides and buttons on top. As the user places palm over the top of the mouse and moves it across the mouse-pad, the ball at the lower side also moves. The movement of the ball determines the location of the arrow or mouse-pointer on the computer screen. A mouse-pointer is a small arrow or other symbol on the computer screen that moves as you move the mouse. There are 3 different shapes of mouse. There are: three-button mouse, scroll mouse and cordless mouse. 3. TRACKBALL: Trackball is an alternative to a mouse. It operates in the same way as a mouse. It is less complicated than a mouse and is designed for the use of children. Turning the ball with your hand moves the pointer on the screen. Trackballs are useful when there is not enough space for a mouse, for instance in portable computers. Most trackballs have buttons which can be used to select options on the screen. OUTPUT DEVICES An output device is a hardware that presents digital information in a form that human beings can understand. They include: PRINTERS The most important output, if the data is needed for human interpretation, is on sheets of printed continuous stationery. This is called hard copy of data. It is produced by devices called printers. The most common type are the line printers. VISUAL DISPLAY UNIT (VDU) The results of the processed data or information first appear on the VDU before it is sent to the printer or the computer system is switched. The VDU produces only a transistor copy. This information can be text or graphical characters. CONNECTIVITY HARDWARE Connectivity hardware is the hardware that allows computers to be physically connected to different types of network. For example connectors, network interface cards, modem, repeater etc.