module 3 introduction to computer system : structure & processes introduction to computer system...
TRANSCRIPT
Module 3Module 3
Introduction To Computer System :
Structure & Processes
Introduction To Computer System :
Structure & Processes
Module ObjectivesModule 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– 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
What is A Computer System ?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
Functions Of A Computer SystemFunctions Of A Computer System
Components Of A ComputerComponents Of A Computer
SystemsInterconnection
i.e. bus
CPU
MainMemory
Input / Output
Communication Lines
PeripheralsComputer
• Complex set of electronic circuitry
• Executes stored program instructions
• Two parts– Control unit– Arithmetic/logic
unit (ALU)
Central Processing UnitCentral Processing Unit
Sends data to
the CPU
Registers
Control Unit
ALUUnit
Processing
InputOutput
Secondary storage
Stores data and programs
Makes processed
info available
Central Processing Unit
Control UnitControl 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
Arithmetic Logic UnitArithmetic 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
Intel Advanced Micro Devices (AMD)
Cyrix Motorola (Apple)
Pentium IVPentium MMX
Pentium III
Popular CPUsPopular CPUs
• 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
Systems Interconnection (Bus)Systems Interconnection (Bus)
Control
Data path
Mem
ory
ProcessorInput
Output
Input / Output BusInput / 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
Expansion CardAGP slots PCI-E slots
Data Storage and the CPUData 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
The CPU and MemoryThe 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
Temporary Storage AreasTemporary Storage Areas
• 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
MemoryRegisters
The Machine CycleThe Machine Cycle
• The time required to retrieve, execute, and store an operation
• Components– Instruction time– Execution time
• System clock synchronizes operations
The Machine CycleThe Machine Cycle
• Instruction Time = I-Time– Fetch – Gets the next 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
OFFON
0 1
OR = 1 bit
1
0
0 0 001 1
0 0 0 01 1
OR
= 1 Byte
= 1 Byte
OFF
0
0
How Computers Represent DataHow Computers Represent Data
• 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
ON
1000 bits = 1 kilobit (kb)
1,000,000 bits = 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
BitsBits
BytesBytes
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
• 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
Storage SizesStorage Sizes
Coding SchemesCoding Schemes
• Provide a common way of representing a character of data
• Needed so computers can exchange data
• Common Schemes– ASCII– EBCDIC– Unicode
0 10 0 001 1= 4
= 4
Representing Characters : Character CodesRepresenting 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
0 001 11 1 1
EBCDIC
Inside the System Unit / CasingInside 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
Drive bays
On/off switch
Reset button
Indicator lights
FRONT
BACK
The front panel contains drive bays, various buttons, and indicator lights
Connectors and ports are physical receptacles located on the back to connect peripheral devices to the computer
Outside the System UnitOutside the System Unit
Types of Connectors / PortsTypes of Connectors / Ports
A 15 pin connector used for monitors
For graphics-intensive interaction
Data flows through eight wires allowing the transfer of eight bits of data
simultaneously; faster than serial ports
Allows up to 127 devices
to be connected at
a time.
keyboard port - Special
serial port to connect keyboard.
Mouse port – Special
serial port to connect
mouse.
Also called jacks, sound card connectors
accept stereo mini-plugs. Microphone, line-in, line-out, and speaker connectors are plugged into the
card.
Serial port – Data flows in a series of pulses, one after another one bit at a time; slow data
transfer rate.
Other Types of ConnectorsOther 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