Session 2:

Computing Components

Nell Dale • John Lewis

Session Goals

Begin to understand the jargon used in computingList the components and their function in a von Neumann machineDescribe the fetch-decode-execute cycle of the von Neumann machine

Session Goals (cont.)

Describe how computer memory is organized and accessedName and describe different auxiliary storage devicesDefine parallel computer configurations

20

Programmer / User

Applications Programmer(uses tools)

User with No Computer Background

Systems Programmer(builds tools)

Domain-Specific Programs

Computing as a Tool

21

Computing as a Discipline

Four Necessary Skills1. Algorithmic Thinking2. Representation3. Programming4. Design

Computer Components

Consider the following ad

Sizes in Perspective

Admiral Grace Murray Hopper A coil of wire nearly 1,000 feet long

Distance traveled by an electron along the wire in the space of a microsecond

A short piece of wire In the space of a nanosecond

A bag containing grains of pepper In the space of a picosecond

Sizes in Perspective

Stored-Program Concept

Figure 5.1 The von Neumann architecture

System Components

Hardware I/O devices (input/output)

keyboard, mouse, monitor, etc. CPU Primary Storage Secondary Storage

Software

Typical System

Computer caseMonitorPrinterSpeakersModemKeyboardMouse

Computer ComponentsPower supplyHard driveExpansion cardExpansion slotSystem boardCD-ROM or DVD-ROMFloppy diskDrive bayCentral Processing Unit (CPU)Random access memory (RAM)

Processing

The Fetch-Execute Cycle

Fetch the next instructionDecode the instructionGet data if neededExecute the instruction

The Fetch-Execute Cycle

Sample Processing Sequence

Two numbers in main memory are added1. Instruction is transferred from memory into the CPU2. Location of the instruction being processed is

updated in the instruction counter (IC) or program counter (PC)

3. The instruction just fetched is stored in the instruction register (IR)

4. CU decodes the instruction to add two numbers• operator [operand1], [operand2], [operand3]• ADDW3 first_no, second_no, answer

• W = words, 3 = no of operands in the instruction

5. Numbers are located in main memory6. Fetched into internal registers of the ALU by the CU7. Addition is carried out by ALU8. Sum stored in new memory location by CU9. The IC is updated to point to the next instruction

Memory

Memory is a collection of cells, each with a unique physical address

Computer Architecture

Microprocessor (examples Pentium, Pentium II, PowerPC, etc.) includes Bus Interface Unit, Arithmetic & Logic

Unit (ALU), Control Unit, registers motherboard is simply the main circuit board

that contains most of these parts the CPU (central processing unit) is considered

to be most of these parts taken as a whole

Bus connects the microprocessor to the RAM & ROM addresses for data and instructions are

important

CPU (Central Processing Unit)

Processes instructions, performs calculations, and manages the flow of information Performance:

CPU speed is a major factor in determining how fast a computer operates (faster the speed, faster computer operates)

Measured in gigahertz (GHz) A clock cycle relates to the clock that controls the timing in the microprocessor.

For example, a 1.4GHz (gigahertz) clocked microprocessor generates 1.4 billion clock cycles per second.

Each generation of CPU is more powerful than the one before. It's clock cycles are faster at a given speed

Processing

The Central Processing Unit (CPU) is the main chip in a computer Processes instructions Performs calculations Manages the flow of information

Types of CPUs (Chips)

Intel Pentium ProcessorIntel Celeron Needs of home machines

AMD Athlon Processor Business and home use

AMD Duron Processor Home use

VIA Cyrix Processor Inexpensive CPU

Main Memory / Primary Storage

Speeds up computer by storing data the computer has recently used Internal Cache: On CPU chip (L1 or primary

cache External Cache: On the system board and

consists of Static RAM (SRAM chips) Sometimes built into chip

RAM – slower main memory Each time the computer requests data from

RAM, the computer places a copy of the data in memory cache Constantly contains the most recently used data

Storage Devices

Primary storage RAM (Random Access Memory, or just

“memory” for short) active data that is being stored, lost if power is cut off

so save often ROM (Read-Only Memory)

commands that are permanently stored on chips PC’s use BIOS, Macs use the Toolbox

Secondary storage Hard disk, floppy disks Slower method of storage & retrieval but

“safer”

Random Access Memory

Random Access Memory – Temporarily stores data inside a computer Constantly overwritten Measured in megabytes (MB)

If you have limited memory or you have many programs open, your computer may need to use part of the hard drive to simulate more memory

RAM and ROM

RAM stands for Random Access Memory Inherent in the idea of being able to access

each location is the ability to change the contents of each location

ROM stands for Read Only Memory The contents in locations in ROM cannot be

changed

RAM is volatile, ROM is not This means that RAM does not retain its bit

configuration when the power is turned off, but ROM does

Using Memory

1. Look through documents on your desk (internal cache)

2. Look through documents in your desk drawer (external cache)

3. Looking through documents in your filing cabinet (RAM)

4. Go out and get it from the trunk of your car (secondary storage)

Control Unit

Control unit is the organizing force in the computerThere are two registers in the control unit The instruction register (IR) contains the

instruction that is being executed The program counter (PC) contains the

address of the next instruction to be executed

ALU and the control unit called the Central Processing Unit, or CPU

Arithmetic/Logic Unit

Performing basic arithmetic operations such as addingPerforming logical operations such as AND, OR, and NOTMost modern ALUs have a small amount of special storage units called registers

Input/Output Units

An input unit is a device through which data and programs from the outside world are entered into the computer Keyboard, the mouse, and scanning devices

An output unit is a device through which results stored in the computer memory are made available to the outside world Printers and video display terminals

Math Coprocessors

A special processing unit that assists the CPU in performing certain operations. A math coprocessor is a chip or part

of a chip that specializes in doing math. Hardware that attaches to the motherboard or is part of the CPU.

Also called numeric coprocessors or floating point units (FPU).

Flow of Information

The parts are connected to one another by a collection of wires called a bus

Figure 5.2 Data flow through a von Neumann architecture

Bus

Electronic pathway that carries information between devices in a computer Bus Width (think lanes of a highway)

8 bits is one character Bus Speed (think speed limit)

Measured in MHz (millions of cycles per second)

Parallel Processing

Synchronous processing

One approach to parallelism is to have multiple processors apply the same program to multiple data sets

Figure 5.6 Processors in a synchronous computing environment

Pipelining

Arranges processors in tandem, where each processor contributes one part to an overall computation

Figure 5.7 Processors in a pipeline

Peripherals

Ports

Ports are connectors at the back of a computer system that you use to plug in an external device. This allow instructions and data to flow between the computer and the device

Any Port in a StormParallel port – 25 holes; female connector; LPT1; printer or storage devicesMonitor portKeyboard portSerial port – 9 or 25 pins; male connector; COM1; mouse or modemGame portNetwork portUSB port

127 devices Printer, modem, joy stick

Firewire

USB and Firewire

High-speed ports that allow information to quickly transfer between a computer and an external device USB

Supports up to 127 device USB 1.0: 12 megabits per second USB 2.0: 480 Mbps

FIREWIRE 63 devices at 400 Mbps Can purchase Firewire expansion card

Storage Devices

Secondary Storage Devices

Because most of main memory is volatile and limited, it is essential that there be other types of storage devices where programs and data can be stored when they are no longer being processed Secondary storage devices can be installed within the computer box at the factory or added later as needed

Magnetic Disks

A read/write head travels across a spinning magnetic disk, retrieving or recording data

Figure 5.5 The organization of a magnetic disk

Hard Drives

Magnetically stores data on rotating disks called plattersCapacity is measured in bytesSpeed is measured in revolutions per minute

Floppy Drives and Drives

Removable media Can be write-protected Can be damaged magnetically

Magnetic Tape

The first truly mass auxiliary storage device was the magnetic tape drive

Figure 5.4 A magnetic tape

Tape Drive

Backup helps you copy files to tape cartridgesTry to find a drive that can store the entire contents of your hard drive

Removable Storage Devices

Jazz Drive – 2 GBZip Drive – 250 MBLS-120 Drive – 120 MB

Compact Disks

A CD drive uses a laser to read information stored optically on a plastic diskCD-ROM is Read-Only MemoryDVD stands for Digital Versatile Disk

CD-ROM

ROM (Read-only memory) - can’t be changed650 Mb of data Equal to entire set of encyclopedias 400 Floppy disks

Speed determines how fast a disk spins Look for 48X

Speed of CD-ROM drive is the transfer rate In Kb (e.g. 3600Kbs)

CD-R & CD-RW Drives

CD-R (Compact Disc – Recordable) Permanent store; not erasable

CD-RW Can be erased and rewritten Read / Write and Re-write speeds Usually 74 minutes

Special software needed to record onto a disk Referred to as burning a CD

DVD-ROM Drive

DVD – Digital Versatile Disk Generally cannot change the information

stored on a disk Similar to CD but stores more information Speed determines transfer rate (6 X) Capacity

1 side / 1 layer – 4.7 GB 1 side / 2 layer – 8.5 GB 2 sides / 1 layer – 9.4 GB 2 sides / 2 layers – 17 GB

Input and Output

Input Devices

KeyboardsMice Trackballs Pointing Devices

Scanners

A scanner is a device that reads images and text into a computer Optical Character Recognition

(OCR) software that places scanned text into a document that can be edited in a word processor

Color depth is measured in bits and indicates the number of colors a scanner can detect

Resolution

Resolution determines the amount of detail a scanner can detect

Ranges from 600 dpi to 2400 dpi You usually don’t need to scan at a

higher resolution than a printer can produce or a monitor can display

Most monitors are 72 dpi Printers vary

Output Devices

Printers

Speed of a printer is measured in pages per minute (PPM). A higher speed represents faster outputResolution determines the quality of images A higher resolution results in sharper images Printer resolution is measured in dots per inch

(dpi) 600 dpi is acceptable; 1200 is better for images

Resolution expressed with two numbers represents dots per inch across and down

Types of PrintersInk-jet: has a print head that sprays ink through tiny nozzles onto a page 2 to 10 pages (ppm) 360 to 2400 dots per inch Color printers spray cyan, magenta,

yellow and black to create different colors

Laser-printer Works like a photo copier Speed of 4 to 16 pages Have a CPU 600 to 2400 Memory – 2mb to 8 Mb

Print Buffer and Spoolers

Printer buffer: section of memory printer stores information waiting to printPrinter spooler: program on your computer that stores information waiting to print Stores more information than the buffer One spooler for each connected printer

MonitorsVideo cards translate instructions from the computer into a form Most computes the monitor can understand require at least 2 mb of video

card memory

Monitor Metrics

The smaller the dot pitch, the crisper the image 0.28mm is acceptable

Refresh rate is measured in hertz (Hz) Times per second computer redraws

the image 72 Hz or more is acceptable

Communications

Modems let a computer exchange information through telephone linesSpeed of a modem determines how fast it sends and receives messages 56,000 bps (56 Kbps)

V.90 standard: receive 56K and send 33.6K

Speed at which information flows depend on the quality of the phone line

High-speed Connections

ISDN – Integrated Services Digital Network Digital phone line 56 Kbps to 128 Kbps

Cable Modem Same cable as TV 4000 Kbps

DSL – Digital subscriber line High speed digital phone line 1000 – 6000 Kbps

Operating Systems

Operating Systems

Software that controls the overall activity of the computer Ensure that all of the parts of the computer

work together smoothly Functions:

Control hardware Run software Manage information

Programs that run on one operating system platform do not generally run on others

Software: Systems Software

Operating systems Controls the hardware components

(disks, CPU, printers, etc.) Windows XP, Windows NT/2000,

Windows 9-X, MS-DOS, OS/2, MacOS, Unix, Linux, BeOS

Types of Operating Systems

MS-DOS Command driven

Windows Windows 3.1 Windows 9X (95, 98) Windows ME Windows XP Windows NT Windows 2000

UNIXMAC OS

Unix

Can run single computer or entire networkDeveloped on mainframes in late ’60’sTrue multi-tasking OSMost widely used operating system on Internet

LINUX

Unix-based system offered as freeware on the Internet

Software

Software

System software runs the machineApplication software helps you accomplish specific tasksManufacturers also may create minor software updates called patches, to make corrections or improvements to software

Utility Programs

Utility: A program that performs a specific task on your computer Norton utilities: recover files Virusscan: anti-virus software Acrobat Reader: View PDF (Portable

Document Format) files Winfax pro ViaVoice – Speech recognition WinZip – Compress and decompress files

Application Software:

Word processorSpreadsheetsPresentation SoftwareDatabase SoftwareInternet Software

Software: Application Software

Office products Word processors Spread sheets Presentation software Email

Business applications General ledger Financials

Accounts payable Accounts receivable

HRMS Fixed assets/inventory

Database Programs

Helps you manage large collections of related informationUses Store information Find information Analyze and print information

Databases

Organized in: Tables

Collection of information about a specific topic

Field Category of information

Record Single instance of information

Programming Software

Text Editor Used by the programmer while coding

the program in a programming language Like a word processor - creates a text file

containing the program's instructions or "source code"

Examples are “nled” and “vi” editors in Unix systems

Other editors are NotePad and WordPad which are text-based

Programming Software

Interpreters Translates source code into machine code line

by line

Compiler Translates source code into an object file, than

uses linker to create an executable file A source module (source code) becomes an "object"

module (compiled module) Then it is linked with system modules to become a

"load" module (linked module)

It is usually more efficient to use a compiler