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Catholic University College of Ghana Fiapre-Sunyani. HARDWARE. INFORMATION TECHNOLOGY I. Audrey Asante, Faculty of ICST. System Unit. The standard color coding scheme for the keyboard connector, port, cable is purple but not all manufacturers follow the color scheme.

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catholic university college of ghana fiapre sunyani

Catholic University College of GhanaFiapre-Sunyani



Audrey Asante, Faculty of ICST

The standard color coding scheme for the keyboard connector, port, cable is purple but not all manufacturers follow the color scheme.
  • The standard color coding scheme for the mouse connecter, port, cable is green.
  • PS/2 connections and disconnections can cause damage to the computer.
  • Universal Serial Bus is the new technology of adding any new peripheral without using the ps/2 or serial or parallel connection. It can be plugged and unplugged easily.
  • Sockets on the outside of the system unit that is connected to the board on the inside of the system unit. It allows you to connect a peripheral device such as a monitor, modem, printer etc
  • Types
    • Parallel ports are used to connect external devices that need to send or receive a lot of data over a short distance. These ports typically send eight bits of data simultaneously across eight parallel wires. Parallel ports are mostly used to connect printers to system units. example is the printer port, scanners, external storage media. It has 25 pins connector.
  • Serial ports are used for a wide variety of purposes. They are used to connect a mouse, keyboard, modem, and many other devices to the system unit. Serial ports send data one bit a time and are very good for sending information over a long distance. It comes in two sizes, 9 pins and 25 pins.
  • Universal Serial Bus (USB) ports are expected to gradually replace serial and parallel ports. They are faster, and one USB port can be used to connect several devices to the system unit
  • FireWire ports are the newest type. They are even faster than USB ports and are used to connect high-speed printers and even video cameras to the system unit.
  • Accelerated graphics ports (AGP) are used to connect monitors. They are able to support high-speed graphics and other video input.
  • It is the main circuit board in the system unit. It houses the essential components of the computer. Every component is connected to the motherboard for the computer to make use of it.
power supply
  • It converts Alternating Current to Direct Current for the computer to use. The power supply should be able to supply the right current for the motherboard to use. They should match when replacing the power supply of a computer. All peripherals and devices are connected to the power supply to provide the necessary power. The wires from the power supply are connected to the various drives.
It is not healthy for your computer to go off immediately the light goes off or when there is not power. You can use a UPS (uninterruptible power supply) which will provide the computer with electricity when the power goes off. You can also use the surge protector( protect when there is a surge of high voltage) or voltage regulator when there is insufficient power.
access slots
Access Slots
  • They are opening at the back of the computer to allow devices to be connected
  • Microprocessor processes or manipulates data into information. If found in any machine other than the computer, the microprocessor is called a microcontroller or embedded computer. It is the brain of the computer. It is made up of two parts; CU/ICU and ALU. The components in the computer system are linked together by bus.
types of alu
  • Different types of ALUs are designed to do arithmetic operations at different speeds. The faster they work, the more the cost.
  • Serial-by-bit ALU: its operation involve a single pair of bits at a time, one for each operand. It is a slow process. They are found in few specialized systems
types of alu1
  • Parallel ALU: It does calculations fast because for faster calculations, one needs more transistors in the ALU arithmetic circuits, to process all of the digits in the operand (all of the bits in the computer words) simultaneously.
  • A word is the number of bits (such as 16, 32 or 64) that can be accessed at one time by the CPU. The more bits in a word, the more powerful and the faster the computer is.
  • The system clock can be found in the processor.
  • The system clock controls the speed of operations within a computer. The faster the clock speed, the faster the computer can process information.
  • Machine Cycle/Fetch-execute-cycle
  • A computer speed is measured in MIPS, millions of instructions per second.
  • The processor speed determines how fast the computer gets things done.
cpu chips
  • Most personal computers use two kinds of CPU chips. Intel-type chips and Motorola-type chips.
  • Intel-type chips: developed by Intel corporation for PCs like IBM, Compaq, Dell, Gateway 2000, NEC. The higher the number example 486, the faster the processing speed. Since 1993, new CPU chips bear the names Pentium, Pentium Pro, Pentium MMX, Pentium II.
architecture of microprocessor
  • CISC: complex instruction set computing is mostly used in personal computers and in conventional mainframes. It supports large number of instructions. E.g. are Intel’s Pentium II and III. It is the most widely used chip design with thousands of programs written specifically for it.
  • RISC: reduced instruction set computing is mainly used in workstations. It operates with fewer instructions and RISC-equipped workstations work up to 10 times faster than conventional computers. It is less costly as compared to CISC. It is also found in Apple computers
types of processing
  • Serial: execution of instructions one at a time
  • Parallel: executing more than one instruction at a time
  • Pipelining: this is where the CPU starts a new instruction as soon as the previous instruction reaches the next stage of the machine cycle. Processes speed up.
The processor speed is affected or determined by:
  • System Clock rate: rate of an electronic pulse used to synchronize processing. It is measured in megahertz=I million cycles per second or gigahertz=I billion cycles per second.
  • Bus width = the amount of data the CPU can transmit at a time to main memory and to input and output devices.
The data are transmitted from registers to the ALU, and the result of an operation is transmitted from the ALU to a special register called an accumulator. It is a location in the CPU used to hold, or accumulate the results of ALU operations
coding scheme system
Coding Scheme/System
  • In order to store and represent text in a computer, a scheme must be employed to convert letters, punctuation marks, and special characters to binary numbers (0 or 1). Some of the coding schemes are;

ASCII (used in UNIX and DOS/Windows-based computers)EBCDIC (for IBM System 390 main frames) Unicode (for Windows NT and recent browsers)

binary coded decimal bcd
  • It uses a 4-bit code to represent a decimal digits. Each digit in a decimal number is converted to a 4-bit binary number. It is inefficient to use the BCD because you cannot use 4 bits to represent 10 different values. 4 bits can represent up to 24 or 16 distinct quantities
  • If you have a decimal number 3752, which will be in base 10 when converted to 4 bit BCD, it will be 0011 0111 0101 0010
  • 4 bit BCD was expanded to 6-bit BCD.
ebcdic system
  • Extended Binary Coded Decimal Interchange Code system is an 8-bit BCD code that allows 256 (28) possible bit combination. This code can be used to represent upper-case and lower-case letters, decimal digits, punctuation marks, and special characters.
An example

Character EBCDIC

A 1100 0001

B 1100 0010

9 1111 1001

  • The 4 leftmost bits are the zone bits, and the 4 rightmost bits are the numeric bits. Unique combination of zone and numeric bits represent each character. This code was established by IBM and is used primarily in IBM mainframe computers and peripheral devices.
  • American Standard Code for Information Interchange is a 7-bit code cooperatively developed by several computer manufacturers whose objective was to produce a standard code for all computers. It allows 128 different characters. 7-bit per character. It can handle English Language, math symbols, Greek letters but not all characters.
  • Character ASCII

A 100 0001

B 100 0010

9 011 1010

  • The ASCII is used at least for microcomputers. The ASCII is 7-bit but a bit is added to make 8-bit to check for errors or for error detection.
  • It is a subset of the ASCII. It uses 2 bytes that is 16 bits for each character. It can handle 65,536 character combination instead of the 256 character combination of the ASCII. Even though it handles all alphabets, characters, people still use ASCII or 8-bit standard for software applications and database.
parity bit
Parity Bit
  • It is also called the check bit. It is an extra bit attached to the end of the byte for purposes of checking for accuracy. There are two types, even parity and odd parity. It all depends on the number of on bits to determine whether it is even or odd. If the number of on bits is wrong, there will be an error or an error will occur. You would not know but the computer will know where the error is coming from.
  • Even parity: 01001000, a zero is added to make it even because we already have two 1s.
  • Random Access Memory is also known as the primary storage, internal memory or main memory. It stores data temporal. It is volatile because it is power dependent. Data stored on the RAM can be retrieved easily and fast. It stores currently running programs and their data. It is used for shorter access time and higher data flow speeds. Each byte of the memory has a unique address.
  • It is found or mounted on a circuit board such as a SIMM (single inline memory module) or DIMM (dual inline memory module). SIMM has multiple RAM chips on one side whiles DIMM has multiple RAM chips on both sides.
  • RAM chips can be added by plugging memory-expansion card into the motherboard. The more RAM, the faster the computer operates, and the better your software performs.
types of ram
  • DRAM chips (dynamic random access memory): they are used in microcomputers because they are less expensive.
  • SRAM chips (static random access memory): they are faster than DRAM but more expensive and take up more space and also use more power.
EDO RAM Chips: a newer type of DRAM chip. Extended data out approach performance of SRAM chips. There is increased speed by using the EDO RAM chips because they keep data available for the CPU while it is starting the next memory access.
  • Properties of the RAM
    • Quick access
    • Power dependent (losses all information when there is no power
  • Is the size of the RAM essential factor in terms of the speed of the computer?
  • The ROM is also called the boot loader because it contains the startup program
  • It is involatile because data stored on it cannot be erased.
  • Data or information stored on it is permanent. It is not power dependent
advantages of rom
  • The information they hold is stored in a form that persists even in the absence of power. That is ROMs are nonvolatile
  • They generally cost less and work faster
types of rom
  • Programmable read-only memory (PROM): the contents of a PROM may be loaded by the user
  • Erasable read only memory (EROM): Their contents can be changed to correct errors
  • Erasable Programmable read-only memory (EPROM): Their contents as well can be changed to correct errors.
cache memory
  • Cache-Memory: it is also an auxiliary memory used to accelerate the read and write access to the RAM. It is close to the CPU or found on the CPU to provide short access times.
expansion boards
  • They are circuit boards used to improve the functionality of the computer. Some of the following tasks that the expansion board performs are;
    • Addition of sound card
    • Modems
    • Video cards
    • Network cards
    • Memory expansion cards to allow the addition of a RAM chip
expansion slot
  • Sockets on the motherboard into which one plugs an expansion card.
  • They are used to add drives to the computer. Some of the components put in bays are floppy disk drives, hard disks and removable drives, CD-ROM drives
  • Complementary metal-oxide semiconductor (CMOS) chip provides flexibility and expandability for a computer system. It contains essential information that is required every time the computer system is turned on. The chip supplies such information as the amount of RAM, type of keyboard, mouse, monitor, and disk drives. It is powered by a battery and does not lose its contents when the power is turned off. Its contents can be changed to reflect changes in the computer system such as increased RAM and new hardware devices.
storage media
  • CD-ROM
    • What is the difference between CD-Write and CD-Rewriter?
storage devices
  • Six factor to distinguish secondary storage devices
    • Storage capacity
    • Access speed (average time needed to locate data on a secondary-storage device). Measured in millisecond (thousandths of a second)
    • Transfer rate(speed at which data is transferred from secondary storage to main memory) measured in megabytes per second.
    • Size (portability)
    • Removability
    • cost
hard disk
  • They have short access time and have large capacities.
  • The usage of a jumper can make a hard disk a master or slave.
  • Disadvantage
    • Possible head crash
hard disks
  • Hard disks are connected to the mother board using the technologies EIDE (Enhanced integrated drive electronics) in most computers but we also have the SCSI (small computer system interface). In the EIDE technology, ribbon cables are used to connect. In the SCSI, linkage of devices onto a single expansion board.
hard disk1
  • Virtual memory is the hard disk space used to expand RAM when its space is limited
bus lines
  • Electrical pathway through which bits are transmitted within the CPU and between the CPU and other devices in the system unit. Types are the address bus, control bus, data bus
    • Expansion bus: carries data between RAM and the expansion slots
    • Local bus connects the expansion slots directly to the CPU
bus lines1
  • The system unit has more than one type of bus line. The three principal bus lines or architectures are
    • Industry standard architecture (ISA) was developed for the IBM personal computer. First it was an 8-bit wide data path, then it was 16-bits wide. Although too slow for many of today’s applications, the ISA bus is still widely used.
    • Peripheral component interconnect (PCI) was originally developed to meet the video demands of graphical user interfaces. PCI is a high speed 32-bit or 64-bit bus that is over 20 times faster than ISA buses. It is widely used to connect the CPU, memory and expansion boards.
bus lines2
  • Accelerated Graphics Port (AGP) is the newest bus and over twice as fast as the PCI bus. While the PCI bus is used for a variety of purposes, the AGP bus is dedicated to the acceleration of graphics performance. Widely used for graphics and 3-D animations, the AGP is replacing the PCI bus for the transfer of video data.
  • An 8 bit word bus will be how many times slower than a 32 bit word bus?
  • Dot- Matrix printer: it makes use of pins which hammers letters on the paper. Advantages: cheap or inexpensive, carbon copies are possible. Disadvantages: noisy, slow to medium quality, slow to medium speed, colour fades over time, limited fonts
  • It makes use of small four nozzles that spray the ink onto the paper. It makes use of cartridge. Advantages: high printing quality, low noise, prints color, less expensive than color laser printers. Disadvantages: they are slower as compared to the laser printers because it can print 35-400 cps (character per second) whiles the laser print 8-200 ppm (pages per minute).
laser printer
  • Its printing system is like the photo copier, it makes use of laser beam and also a toner.
  • Advantages: low noise, excellent quality, high speed
  • Disadvantage: expensive especially for colors.
laser printer1
  • There are two categories.
    • Personal laser printers are inexpensive and used by many single users. They typically can print four to six pages a minute.
    • Shared laser printers are more expensive and are used (shared) by a group of users. They can typically print over 30 pages a minute.
  • Two important characteristics of monitors are size and clarity. A monitor’s size is indicated by the diagonal length of its viewing area. Common sizes are 15, 17, 19, and 21 inches. Larger monitors have the advantage of displaying more information at one time; however, they are more expensive.
  • A monitor’s clarity is indicated by its resolution, which is measured in pixels. A pixel are individual dots or “picture elements” that form images on a monitor
  • For a given size monitor, the greater the resolution ( the more pixels), the better the clarity of the image. For a given level of clarity, larger monitors require a higher resolution ( more pixels)
  • Standards to indicate monitor’s resolution capabilities are SVGA, XGA, SXGA, and UXGA
  • SVGA stands for Super video graphics array. It has a minimum resolution of 800 by 600 pixels. It is primarily used with 15-inch monitors.
  • XGA stands for extended graphics array. It has a resolution of up to 1,024 by 768 pixels. It is a popular standard today, especially with 17-inch and 19-inch monitors
  • SXGA stands for super extended graphics array. This standard has a resolution of 1,280 by 1,024 pixels. It is popular with 19- and 21-inch monitors.
  • UXGA stands for ultra extended graphics array. It is the newest and highest standard. It is used in 21-inch monitors. UXGA monitors are primarily used for high-end engineering design and graphic arts.
  • Cathode-ray tube (CRT) is the most common type of monitor for the office and the home. The primary advantages are low cost and excellent resolution. The primary disadvantage is the size.
  • Flat-Panel Monitors or Liquid crystal display (LCD) monitors. The technology for this monitor involves liquid crystals. They are much thinner than CRTs. There are two types;
  • Passive-matrix or dual-scan monitors create images by scanning the entire screen. This type requires little power, but the clarity of the images is not as sharp.
  • Active-matrix or thin film transistor (TFT) monitors do not scan down the screen; instead, each pixel is independently activated. More colors with better clarity can be displayed. They are more expensive and require more power.