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Session 2:. Computing Components. Nell Dale • John Lewis. Session Goals. Begin to understand the jargon used in computing List the components and their function in a von Neumann machine Describe the fetch-decode-execute cycle of the von Neumann machine. Session Goals (cont.). - PowerPoint PPT Presentation
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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
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
System Components
Hardware I/O devices (input/output)
keyboard, mouse, monitor, etc. CPU Primary Storage Secondary Storage
Software
Computer ComponentsPower supplyHard driveExpansion cardExpansion slotSystem boardCD-ROM or DVD-ROMFloppy diskDrive bayCentral Processing Unit (CPU)Random access memory (RAM)
The Fetch-Execute Cycle
Fetch the next instructionDecode the instructionGet data if neededExecute the instruction
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
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)
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
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
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
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
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
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
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
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
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