chapter 3metalab.uniten.edu.my/~nursyazana/cmpf114/chapter 3.pdf · –identify the types of ports...

UNIVERSITI TENAGA NASIONAL“Generates Professionals”

CHAPTER 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

– 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 ?

• A functional unit, consisting of one or morecomputers and associated software, thatuses common storage for the execution ofthe program.

• Consists of three components

– People

• Computer programmer

• Users/End-user

– Software

– Hardware


Functions of a Computer System


Components 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 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 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 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 Apple

AtomCore i7

Core i5

Popular CPUs


Systems Interconnection (Bus)

• 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

Control

Data

path

Mem

ory

Processor

Input

Output


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

Expansion CardAGP slots PCI-E slots


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


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


Temporary 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 Cycle

• The time required to retrieve, execute, and store an operation

• Components– Instruction time

– Execution time

• System clock synchronizes operations


The 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

• 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

How Computers Represent Data


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 persecond (Mbps), and Gigabits per second (Gbps)are terms that describe units of data used inmeasuring data transfer rates

– Example: 56 Kbps modem

Bits


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


• 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 Sizes


Coding 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

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

Representing Characters: Character Codes


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


Drive bays

On/off switch

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 Unit


Types 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 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


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

References

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