SSD2: Introduction to Computer SystemsISS,WHU

Unit 1. Computer Systems1.1 Overview of Computer Systems1.2 Evolution of Computer Systems1.3 Data Representation in a Computer System

Subsystems of a ComputerSoftware SystemOperating System (Unix, Mac OS, Microsoft Windows)Web browser (Netscape, Internet Explorer)Office productivity applications (Microsoft Office, Star Office)Hardware SystemKeyboardMonitorSystem unitNetwork SystemInternet services (email)Network connections (modems, network cards)

Hardware System

Hardware Components: Peripheral DevicesEquipment added to computer to enhance its functionalityModify and expand the basic computer systemExamples of peripheral devices:Keyboard MonitorMousePrinterScannerDigital Video CameraGraphic TabletJoy Stick

Hardware Components: Storage DevicesOptical DisksCD-ROMCD-RWDVD-ROM Magnetic DisksFloppy diskHard disk (removable & fixed)

What is Software?Software is a set of computer instructions or data. Software receives input from the user and processes this input through the computer to produce output.Software directs how the computer interacts with the user. Software specifies how to process the user's data

Software SystemTwo categories:Operating system software, Application software

Software SystemOperating system software, also called system software, is the master controller for all activities that take place within a computerExamples of OS software:Microsoft WindowsUnixMac OSApplication software is a set of one or more computer programs that helps a person carry out a taskExamples of application software: Microsoft WordInternet ExplorerMacromedia DreamweaverAdobe Acrobat Reader

Network SystemA network provides connections among computers to enable computers on a network to share data (e.g. documents), hardware (e.g. printers), and software resources (e.g. application programs).Network users can also send messages to each other.A network must be secured to protect data from unauthorized usage (e.g. using login name and password to gain access to a network).

Basic Computer ModelAll computers perform four basic operationsInput DataProcess DataStore DataOutput Data

Basic OperationsInput data is to feed information which can be supplied by any person, environment or other computer.Processing data is manipulating data by performing calculations, sorting lists of words or numbers, drawing pictures.Storing data is for future retrieval and processing. Memory holds data that is waiting to be processed, and storage areas hold data permanently until the data is deleted.Output data is the result produced by a computer, which includes reports, documents, music, graphs and pictures.

Categories of ComputersComputers are classified based on their technology, function, physical size, performance and cost. The categories of computers include:Personal computersHandheld computersMainframesSupercomputers

Personal Computer (PC)Designed to meet the computing needs of an individualDesktop computers

Notebook computers

Handheld ComputerDesigned to fit into a pocket, run on batteries, and be used while you are holding itAlso called a PDA (Personal Digital Assistant)Send and receive e-mailUse maps and global positioningMaintain expense account, contacts, to-do lists, memos, etc.Make voice calls using cellular service

A personal digital assistant (PDA) accepts info on a touch-sensitive screen

Mainframe ComputerIt is a large and expensive computer that is capable of handling requests and passing data simultaneously to many users.Used by governments and large corporations to provide centralized storage and controlProcesses billions of data per second and includes many units where one directs overall operations, a second one handles communication between users, and third searches for requests given by user.

SupercomputerIt is the fastest type of computer.Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. It is often used for:Breaking codesModeling weather systemsSimulating nuclear explosionsResearch simulationsCapable of performing over 600 billion floating-point operations per second. Examples: Deep Blue, PARAM 1000, Hitachi's SR2201

Evolution of ComputersNeeded calculation devices to keep track of accounting for commerce1200sManual Calculating Devices: the abacus

Evolution of Computers (continued)1600sMechanical CalculatorsUsed wheels, gears, and counters To work a mechanical calculator, the operator enters the numbers for a calculation, and then pulls a lever or turns a wheel to carry out the calculationExample: the Pascaline invented by Blaise Pascal. It used some principles of the abacus, but used wheels to move counters.

Evolution of Computers (continued)1800sPunched Cardspunched card Used holes following a specific pattern to represent the instructions given to the machine or stored dataDifferent program instructions can be stored on separate punched cards, which can be fed through the computing machine repeatedly. Once punched, the cards were fed into a card reader that used an array of metal rods to electronically read the data from the cards and tabulate the results. This is called the Hollerith Tabulating MachineHollerith incorporated The Tabulating Machine better known today as IBM.

Evolution of Computers (continued)Charles Babbage designed a new general-purpose calculating device, the Analytical Engine, which is the ancestor of modern computers. It included the essential components of present-day computers, which are input, process, storage, and output of data.

Evolution of Computers (continued)1940sVacuum Tubes Used to control the flow of electrons. Since vacuum tubes responded faster than mechanical components, faster computations were possible. But, the tubes consumed a lot of power and burned out quickly.

The first computer prototype using vacuum tubes was ENIAC (Electronic Numerical Integrator and Computer). It was designed to calculate trajectory tables for the U.S. Army during World War II, but it was not completed until three months after the war.

Evolution of Computers (continued)1950sTransistors Smaller, cheaper, more reliable, and consumed less power than vacuum tubes. Could perform 200,000 to 250,000 calculations per second.

Evolution of Computers (continued)1960sIntegrated Circuits Thin slice of silicon packed with microscopic circuit elements such as wire, transistors, capacitors, and resistors. Enabled the equivalent of thousands of vacuum tubes or transistors to be packed onto a single miniature chip about the size of your fingernailReduces the physical size, weight, and power requirements for devices such as computers

Evolution of Computers (continued)1970s to PresentMicroprocessor Combined components of a computer on a microchipCan be manufactured and then programmed for various purposes

Evolution of Computers (continued)Pace of Processor Advancement

Applications of Computer SystemsIn Education Multimedia-Facilitated Learning Simulation-Based Education Intelligent Machine-Based Training Interactive Learning In Business Supply Chain Management Project Management Customer Relationship Management Sales and Marketing Using Electronic Commerce Manufacturing Research

Applications of Computer SystemsIn Entertainment Movies Video Games MusicDigital Photography Travel Wearable Computer Systems Developing new applications of computer systems:Research at Carnegie Mellon Universityhttp://www.cs.cmu.edu/research/projects/Research at Massachusetts Institute of Technology Media Lab http://www.media.mit.edu/

Computer IndustryComputer industry encompasses those companies that manufacture handheld computers, personal computers, high-end workstations, servers, mainframes, and supercomputersInformation technology industry (or IT industry), is typically used to refer to the companies that develop, produce, sell, or support computers, software, and computer-related productsIT companies include:Equipment manufacturersChipmakersSoftware publishersService companiesRetailers

Computer Industry (continued)The 1990s spawned a group of Internet-based companies that came to be called dot coms, from the companies domain names, which inevitably ended with .com and many of the companies even incorporated .com into their official company namesAmazon.com was one of the first Internet-based companies

Computer Industry (continued)Governments and private businesses have discovered that they can become much more efficient with a liberal application of computers and other information technologiesAs businesses globalize, they encounter new competitors with technological advantagesBottom line: if your business competitors turn to technology, so must you

Careers in ComputingA systems analyst investigates the requirements of a business or organization, its employees, and its customers in order to plan and implement new or improved computer servicesA security specialist analyzes a computer systems vulnerability to threats from viruses, worms, unauthorized access, and physical damageA computer programmer designs, codes, and tests computer programsA quality assurance specialist participates in alpha and beta test cycles of softwareA database administrator analyzes a companys data to determine the most effective way to collect and store it

Careers in Computing (continued)A network specialist/administrator plans, installs, and maintains one or more local area networksA computer operator typically works with minicomputers, mainframes, and supercomputersA computer engineer designs and tests new hardware products, such as computer chips, circuit boards, computers, and peripheral devicesA technical support specialist provides phone or online help to customers of computer companies and software publishers

Careers in Computing (continued)A technical writer creates documentation for large programming projects, and writes the online or printed user manuals that accompany computers, peripheral devices, and softwareA computer salesperson, or sales rep, sells computersA Web site designer creates, tests, posts, and modifies Web pagesA manufacturing technician participates in the fabrication of computer chips, circuit boards, system units, or peripheral devices

Careers in Computing (continued)The U.S. Bureau of Labor Statistics (BLS) projects that the number of jobs in the computer industry will substantially increase between now and 2008According to the BLS, the largest increases in available jobs will be for database administrators, computer support specialists, and computer engineersOver the next few years, economic trends may cause significant changes in the job marketA daily look at in-demand tech skills can be viewed at: http://mshiltonj.com/sm/

IT Salaries in the U.S.Source: http://www.bls.gov

1.3 Data Representation in a Computer System 1.3.1 Bits and Bytes1.3.2 Number Systems

1.3.1 Bits and BytesRecall computers are made up of electrical componentsData can be represented electronically with electrical components being on or off. On and off states can be represented using digits 0s and 1s. For example: 0: Off state1: On stateThus, data can be represented digitally using digits 0 and 1. 0 and 1 are called binary digits.Each binary digit is called a bit.Eight Bitsequal to one byte .

Data Representation Using Binary DigitsA piece of data, such as an alphabet letter, may be represented using a sequence of binary digits- 0's and 1's. There are several types of codes used to represent character data. Extended ASCII (America Standard Code for Information Interchange) code, the alphabet letter "a" can be represented using a series of eight binary digits, "01100001."

Extended ASCII codeuses eight bits (or one byte) to represent input characters.

data representingAll data, including audio, visual, and program instruction data can be represented and stored using a sequence of binary digits, or a sequence of bytes.

A file is a collection of data.In some files, the bits of data directly encode individual letters, numbers, and punctuation symbols that make up words and sentences. In other files such as an image file, the bits of data need to be computed in order for them to transform to images that we can interpret.

A file is a collection of data.Most applications encode information in specialized ways that are not readable by humans. such as Microsoft Word or PowerPoint even though Microsoft Word is often used to edit text, a Word document cannot be properly displayed by a simple text editor like Notepad because the document includes information in a format specific to Microsoft Word. Therefore, it must be opened by Microsoft Word to be read. Some files have a header section that indicates which format was used to encode the data in order to allow the computer to reassemble the binary data back into the human-readable form of the document.

Increasing Need for Bytes

Decade1970s1980s1990s2000sOrder of magnitude in Storage capacityThousandsMillionsBillionsTrillionsPrefixKilo (103)Mega (106)Giga (109)Tera (1012)AbbreviationKMGT

In terms of storage, more is betterwhichmore information in the form of both data and programs that act on that data can be stored. Corresponding to the growth in storage capacity, memory capacity is also increasing. Moreover, memory technologies are getting smaller, lighter, and faster, for about the same price.

1.3.2 Number SystemsDecimal: base 10 (digits 0-9)Binary: base 2 (digits 0-1)Hexadecimal: base16 (digits 0-9 and A-F)Each hexadecimal digit represents four binary places. Hex digit can be used as shorthand for binary notationOne Hex digit four bitsOne byte = 8 bits two Hex digits