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MODULE 3

MODULE 3. INTRODUCTION TO COMPUTER SYSTEM: STRUCTURE & PROCESSES. Module Objectives. At the end of the module, students should be able to: understand the concept and functions of a computer system identify the component of a computer

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MODULE 3

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  1. MODULE 3 INTRODUCTION TO COMPUTER SYSTEM: STRUCTURE & PROCESSES

  2. ModuleObjectives • At the end of the module, students should be able to: • understand the concept and functions of a computer system • identify the component of a computer • identify the components of the central processing unit and explain how they work together and interact with memory • describe how program instructions are executed by the computer • explain how data is represented in the computer • understand the concept of bit and byte • identify the types of ports and connectors

  3. What is A Computer System ? • A functional unit, consisting of one or more computers and associated software, that uses common storage for the execution of the program. • Consists of three components • People • Computer programmer • Users/End-user • Software • Hardware

  4. Functions of a Computer System

  5. Components Of A Computer Peripherals Computer CPU Input / Output Systems Interconnection i.e. bus Main Memory Communication Lines

  6. Stores data and programs Secondary storage Makes processed info available Sends data to the CPU Central Processing Unit Control Unit ALU Unit Input Output Registers Processing Central Processing Unit • Complex set of electronic circuitry • Executes stored program instructions • Two parts • Control unit • Arithmetic/logic unit (ALU)

  7. Control Unit • Directs the computer system to execute stored program instructions • Must communicate with memory and ALU • Sends data and instructions from secondary storage to memory as needed

  8. Arithmetic Logic Unit • Executes all arithmetic and logical operations • Arithmetic operations • Addition, subtraction, multiplication, division • Logical operations • Compare numbers, letters, or special characters • Tests for one of three conditions • Equal-to condition • Less-than condition • Greater-than condition

  9. Popular CPUs Advanced Micro Devices (AMD) Intel Core i7 Atom Core i5 Cyrix Apple

  10. shared communication link set of wires used to connect multiple subsystems A Bus is also a fundamental tool for composing large, complex systems The input/output bus provides a pathway so that the microprocessor can communicate with input/output devices Processor Input Control Memory Data path Output Systems Interconnection (Bus)

  11. Input / Output Bus • An input/output bus contains expansion slots which hold expansion cards • ISA (Industry Standard Architecture) slot phased out • PCI (Peripheral Component Interconnect) slots • AGP (Accelerated Graphics Port) slot  usually for graphics card • USB (Universal Serial Bus) • PCI Express (PCI-E)  latest tech. PCI slots AGP slots PCI-E slots Expansion Card

  12. Data Storage and the CPU • Two types of storage: • Primary storage (memory) • Stores data temporarily / volatile • CPU refers to it for both program instructions and data • Holds input to be processed or holds results of processing • Secondary storage • Long-term storage / non-volatile • Stored on external medium, such as a disk

  13. The CPU and Memory • CPU cannot process data from disk or input device • It must first reside in memory • Control unit retrieves data from disk and moves it into memory • Items sent to ALU for processing • Control unit sends items to ALU, then sends back to memory after processing • Data and instructions held in memory until sent to an output or storage device or program is shut down

  14. Temporary Storage Areas Memory Registers • High-speed temporary storage areas • located within the CPU • Work under direction of control unit • Accept, hold, and transfer instructions or data • Keep track of where the next instruction to be executed or needed data is stored • Also known as primary storage / main memory • Often expressed as random-access memory (RAM) • Not part of the CPU • Holds data and instructions for processing • Stores information only as long as the program is in operation

  15. The Machine Cycle • The time required to retrieve, execute, and store an operation • Components • Instruction time • Execution time • System clock synchronizes operations

  16. The Machine Cycle • Instruction Time = I-Time • Fetch– Gets thenext program instruction from the computer’s memory • Decode – Figures out what the program is telling the computer to do • Execution Time=E-Time • Execute – Performs the requested action • Write-back (Store) – Writes (stores) the results to a register or to memory

  17. OFF ON 0 1 0 0 0 0 1 0 0 0 0 1 1 1 0 0 How Computers Represent Data OFF ON OR = 1 bit 0 1 = 1 Byte OR = 1 Byte • Bit (Binary digit) – On or off state of electric current; considered the basic unit of information; represented by 1s and 0s (binary numbers) • Byte– Eight bits grouped together to represent a character (an alphabetical letter, a number, or a punctuation symbol); 256 different combinations

  18. Bits 1000 bits = 1 kilobit (kb) 1,000,000bits = 1 megabit (mb) 1,000,000,000 bits = 1 gigabit (gb) • Kilobits per second (Kbps), Megabits per second (Mbps), and Gigabits per second (Gbps) are terms that describe units of data used in measuring data transfer rates • Example: 56 Kbps modem

  19. Bytes 8 bits = 1 Byte 1024 Bytes = 1 Kilobyte (KB) 1,048,576 Bytes = 1 Megabyte (MB) 1,043,741,824 Bytes = 1 Gigabyte (GB) 1,099,511,627,776 Bytes = 1 Terabyte (TB) • Kilobyte, megabyte, gigabyte, and terabyte are terms that describe large units of data used in measuring data storage • Example: 20 GB hard drive • Each byte has 256 (28) possible values

  20. Storage Sizes • Kilobyte:1024 (210) bytes • Memory capacity of older personal computers • Megabyte: roughly one million (220) bytes • Personal computer memory • Portable storage devices (diskette, CD-ROM) • Gigabyte: roughly one billion (230) bytes • Storage devices (hard drives) • Mainframe and network server memory • Terabyte: roughly one trillion (240) bytes • Storage devices on very large systems

  21. Coding Schemes • Provide a common way of representing a character of data • Needed so computers can exchange data • Common Schemes • ASCII • EBCDIC • Unicode

  22. 0 1 0 0 0 1 1 1 1 1 0 0 0 0 1 1 Representing Characters: Character Codes • Character codes translate numerical data into characters readable by humans • American Standard Code for Information Interchange (ASCII) – Eight bits equals one character; used by minicomputers and personal computers • Extended Binary Coded Decimal Interchange Code (EBCDIC) – Eight bits equals one character; used by mainframe computers • Unicode – Sixteen bits equals one character; over 65,000 combinations; used for foreign language symbols ASCII = 4 EBCDIC = 4

  23. Inside the System Unit / Casing • Motherboard (mainboard) – Large printed circuit board with thousands of electrical circuits • Power supply – Transforms alternating current (AC) from wall outlets to direct current (DC) needed by the computer • Cooling fan – Keeps the system unit cool • Internal Speaker – Used for beeps when errors are encountered • Drive bays – Housing for the computer’s hard drive, floppy drive, and CD-ROM / DVD-ROM drives

  24. Outside the System Unit Drive bays On/off switch Indicator lights FRONT BACK • The front panel contains drive bays, various buttons, and indicatorlights • Connectors and ports are physical receptacles located on the back to connect peripheral devices to the computer

  25. Types of Connectors / Ports Mouse port – Special serial port to connect mouse. Data flows through eight wires allowing the transfer of eight bits of data simultaneously; faster than serial ports For graphics-intensive interaction keyboard port - Special serial port to connect keyboard. Allows up to 127 devices to be connected at a time. Serial port – Data flows in a series of pulses, one after another one bit at a time; slow data transfer rate. A 15 pin connector used for monitors Also called jacks, sound card connectors accept stereo mini-plugs. Microphone, line-in, line-out, and speaker connectors are plugged into the card.

  26. Other Types of Connectors • Small computer system interface (SCSI) port – A parallel interface that enables up to eight devices to be connected to it • 1394 (FireWire) port – A high-speed connection for up to 63 devices • Infrared Data Association (IrDa) port – Infrared signals are used to communicate between peripheral devices and the system unit

  27. References • Slides adapted from course materials of Daley, B. “ Computers Are Your Future 2006, Complete Ed”. Prentice Hall, 2006.

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