What is a computer?

• A computer is a physical device that takes data as input, transforms these data by executing a stored program, and outputs information to a number of devices.

Input data ProcessingInformation as output to devices

Stored program

Types of computers

COMPUTER

ANALOG DIGITAL HYBRID

Organization-wide system

Work-group system

Personal Information System

Supercomputers,Mainframes Minicomputers.workstat

ionsPCs, laptops,notebooks

Computer hardware for information system

A computer system consists of interrelated components –computer hardware, software and peripheral devices –that convert data into information.

Basics of data representation

Data – numbers, alphabets,symbols, graphs images –external data representation

Computer –understands data through bits. Bit is smallest unit of data in a computer (1 or 0).

Byte - Unique combination of 8 bits (megabyte, gigabyte, terrabyte)

Most important characteristics of computer hardware

1) Speed – rate at which computer can process data and instructions – number of instructions processed per second. Processing time millionths of a second

2) Size –The amount of memory required to store the data and instructions

Types of digital computers

• Microcomputers –PCs smaller than mainframes but have become sophisticated. Four basic units of PC a) video display unit (VDU), a keyboard and a mouse. It consists of processor where data input, processed, stored and retrieved. This unit also contains primary memory, disk drives, a power supply and outlets for connecting input and output devices

Types of digital computers

• Laptops and notebooks-mobile computing technology. Battery operated portables and can be used any time and anywhere.

-Powerful microprocessors, graphic capabilities, adequate memory size.

• Hand-held computers and pen-based computers (electronic writing pad and a light-sensitive electronic pen, no keyboard)

Types of digital computers

• Minicomputers and workstationsWorkstations: faster and more sophisticated than PCs –

number of productivity tools that increase their efficiency.e.g. SPARC stations from Sun microsystems

Supercomputers- Fastest, most powerful and largest computer.- Multiple

processors –parallel processingMainframe- Extensive memory and high processing speed.

Organization-wide systems –payroll, airline reservations, Serve many servers at same time. Expensive to purchase,

operate and maintain. Trained personnel for maintenanceThe distinction between computer type is becoming very

blurred

Basic components of computer system

Central Processing Unit (CPU)

Control Unit

Primary Storage Unit

Arithmetic and logic unit

Input dataOutput information

Secondary Storage unit

Input unit

• Input unit: Four basic ways to enter data into a computer.

-Keyboard device-numeric keys, cursor control keys, function keys

-Pointing devices – Mouse, touchscreen

Source data automation devices: reading of data directly from documents or objects- optical reading and magnetic reading

Input Technology

• The type of processing will affect the way in which data will be captured.

• Batch Processing –check processing in a bank

• On-Line Processing-ATM, Airline reservation

• On-Line with Delayed Processing –order through toll free number

Central Processing Unit

• Control Unit- Accesses data and instructions in computers and transfers to ALU

• ALU(Arithmetic Logic unit)-Processing of data including addition,subtraction and logical operations

• Primary storage –Temporarily used to store data and instructions. Consists of chips with circuits (Integrated Circuits)

• Primary memory -(RAM)-Volatile memory (semi conductor)

-(ROM)-Non volatile-Basic instructions frequently used by hardware vendors -PROM - Programmable Read-Only Memory

Central Processing Unit (continued)

-EPROM - Erasable Programmable Read-Only Memory. Retains memory until exposure to UV light.. Used to change contents of PROM before shipment

Cache memory(Volatile)-Physically located closer to CPU than RAM. Retrieve information from cache memory more quickly by processes in execution

• Registers(Volatile memory). Located in ALU and CU.Increase efficiency of CPU.Include address registers, instruction registers, general purpose registers (data and address),accumulators

Secondary storage devices

• Long term storage of programs and data outside of the CPU and primary memory (RAM)

• Non-volatile• Slower than primary memory • Magnetic disks –floppy and hard discs.• Hard disk –Mb to Gb of memory. Large storage

capabilities. New technologies such as RAID - Redundant Array of Inexpensive Disks and ZIP drives

• Magnetic tapes-historical data or backups of important files. Low cost and portable. Data accessed sequentially

Secondary Storage

• -Optical disk• CD-ROM (Compact disc –Read only memory)-Optical

disc. Storage capabilities between 440 MB and 1 GB. Stores pictures, video, animation and graphics.

• Magneto-optical disk - erasable rewritable optical disks.Storage important since data loss can cause heavy

financial losses to an organization.

Output devices

Displayed output devices- Video displayed terminal

Printed output devices –Printers –Line printers, character printers, ink jet printer, laser printer, page printers

Speech output devices-Speakers.Sound generated by sound board used in business applications

PlottersMicroform- printing documents on microfilm

Multimedia

• The use of two or more media types in a computer based application.

• Input devices can include cassette decks, cd players, video, still pictures etc.

• Output generally includes high resolution monitors and stereo speakers

Machine Cycle

• Instruction CycleI-cycle

– Retrieve instruction– Decode Instruction– Place in Instruction &

Address Registers

• Execution CycleE-cycle

– Move data to storage area

– ALU performs the operation of instruction

– place result in Accumulator

How Data is Represented

• Use Binary notation - two states 1 or 0

• A binary digit (1 or 0) is called a bit.

• Characters & symbols represented using a coding scheme:– EBCDIC - Extended Binary Coded Decimal

Interchange Code) 8bit– ASCII - American Standard Code for

Information Interchange. orig. 7bit now 8bit

Processor Speed & Size

• Processor speed Measured in MIPS - Millions of Instructions Per Second.

• Storage capacity is measured in Bytes. One Thousand Bytes (1024 bytes) equals a Kilobyte.

Processor Speed & Power

• Word length, Bus Width, Clock Speed, Word Length - Number of Bits that can be processed at once.

• Bus Width- Number of bits that can be moved at once.

• Clock speed - Measured in megahertz (MHz)

Processor Generations

• 1951-1958 - Vacuum-Tube

• 1959-1963 - Transistors

• 1964-1979 - Integrated circuits

• 1980-now - Very Large-Scale Integrated Circuits (VLSIC)

Technology Trends

• Distributed Processing

• Downsizing - networks of micro’s, cooperative processing

• Fifth Generation - Massively parallel processing

• Superchips - special purpose chips.

Computer software for Information Systems

• Software (or programs) is what controls the computer. A software program is simply a list of instructions to tell the computer what to do.

• Data are the raw facts that the hardware and software act upon.

• Software in an organization can monitor sales volume, generates reports, monitors employee attendance, processes marketing information, tracking inventory, etc

• Systems in organizations are driven by programs in programming languages

How Software Comes To Be

User has a Problem Programmer writes Source Code

Source Code Compiled or interpreted

Object Code run by computer

Source Program

Translate

Object Program OutputInput data

Translation process

How software runs

Object Code and Data loaded

into Primary Storage Program using

OS and hardware

• Results placed in primary storage

Example of creating and writing a program

• Programmer starts C compiler and enters source code - saved to file firstpg2.cpp

• The source code is compiled to create the object code file firstpg2.odj

• The object file is then linked to create and executable file - firstpg2.exe

• When run the exe file is loaded into ram and executed

Programming languages

• Two types of programming languages

-procedural and non-procedural.

-Procedural- stepwise sequential explanation to perform a given task

-Non –procedural- focuses on what needs to be done without specifying how it should be done.

Types of programming languages

• First Generation Language –Machine Language- Early computers programmed in this language –series of zeros and 1s which CPU can interpret and execute.

• Programming language – resemble human communication.

• Source program- Program written by programmer

• Object program –machine language• Translator- System software that translates

source program into object program.

Types of PL

• Second generation Languages- the Assemblies. First translators – Assemblers

- allows coding in assembly language e.g. mnemonic (DIV for divide) and symbolic names such as (PAYRATE) for data processed.

- 1-1 relationship between source and object instructions.

Disadvantages- Programs lengthy and difficult to read- Assembly languages different for every model of CPU

Types of PL

• Third Generation Language (3 GLs) – Compilers and Interpreters- Produce multiple object program instructions from a single source program instruction.(Fewer lines of code). Syntax more user friendly e.g. BASIC, FORTRAN, COBOL

COBOL and FORTRAN – Compiler languagesBASIC – Interpreter language3 GLs can be executed on different computers-

Portability

Types of PL

• Fourth Generation Languages (4GLs)- Non procedural languages. Programmer instructs computer what to do and not how to do it. (Query based)

• Natural language similar to everyday speech

Friendly Unfriendly

User-friendliness

Much

Little

DSS

power

Database query languages

Graph generators

Modeling Languages

Very high level languages

Report writers

Application generators

Types of PL

• Database Query Language – Manager can use database query language that provides a special report from database contents without coding.e.g sales report

• Modeling languages – Easier mathamatical models- SLAM, MODEL

• Very high level languages –Programming languages –API -Application Programming Interface

Types of PL

• Graph generators - graphic package

• Report writers- Prepare reports e.g. in database management systems

• Application Generators- Application generator produces application program such as inventory or payroll without programming e.g. MANTIS

Types of PL

• Object-Oriented Programming

-Programming language to enhance productivity of programmers and reduce software development time.Chunks of programming and data called objects are used. Each object includes programming code that specifies how it behaves, how to manipulate data etc. Advantage code –usability.

Visual Programming

-Visual programming to visualise code and impact on system.e.g. Visual Basic

Classification of software

• System software

- System control software- Monitor, control, coordinate and manage resources and functions of a computer system. System control software divided in

1) Operating system and its functions

2) Operating system environments

Classification of software

• System control software• Operating system and its functions- Schedule jobs- Manage hardware and software resources- Maintain system security- Enable multiple user resource sharing- Handle interrupts- Maintain usage records

Classification of software

• System control software

• Operating system environment

- Multiprogramming – multiple users run multiple programs on a single-CPU computer at the same time.

- Multiprocessing- No of processors that process data and instructions

- E.g. of OS –Unix, DOS

Classification of software

• System support software –programming services software (assemblers, compilers, interpreters),security software, system documentation, Utility programs are utilities used for repetitive tasks such as backup utilities.

• System development software- Design and build better systems

Language Translators

• Used to convert source code into object code, ie human form into machine language.

• Compilers - translates an entire program into machine language to create an executable file.

• interpreter - translates a program one line at a time into machine code and executes it.

Application software

• Manage organizations’s physical and conceptual resources to meet information needs

-General purpose software- word processing, spreadsheets

- Dedicated software – customized applications e.g. logistics software

Software Relationships

Users

Application Software

System Software

Hardware

Role of software in problem solving

• Software can play a direct or indirect role in problem solving. Most general business and industry- specific packages are designed to play an indirect role by creating and maintaining database that provides the basis for information-oriented subsystems.

Criteria for investment determined by financial criteria, management criteria ( support of business objectives etc., technical requirement, tech support)

Data Organisation - key terms

bit 1 or 0 (binary digit)

byte 1010 0001

field unit of information –combining several fields gives relevant info about database

record (a collection of fields)

file/table a collection of records

database a collection of files/tables

Data Organisation - key terms

• Entity - person, place, or thing that we wish to collect information on (eg students).

• Attribute - a characteristic of an entity (eg student name, student address). Is equivalent to a Field in the data hierarchy.

• Key Field - a special field that uniquely identifies a single record (eg student number)Can be a collection of fields.