computer system overview 1

The Effects of Computers

• Pervasive in all professions

• How have computers affected my How have computers affected my life?life?

• InternetInternet• Computer LiteracyComputer Literacy

–    knowing how to use the computerknowing how to use the computer– knowing capabilities and limitsknowing capabilities and limits

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History of ComputersHistory of Computers

• First Generation computers (1951-First Generation computers (1951-1958)1958)– vacuum tubesvacuum tubes– used large amounts of electricity, heatused large amounts of electricity, heat– large and expensivelarge and expensive– 1946 - ENIAC - computed trajectories for 1946 - ENIAC - computed trajectories for

U.S. ArmyU.S. Army– 1951 - UNIVAC - first commercially 1951 - UNIVAC - first commercially

available computeravailable computer

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• Second Generation computers (1959-1963)Second Generation computers (1959-1963)– Transistors,less heat,more reliable, less Transistors,less heat,more reliable, less

expensiveexpensive

• Third Generation computers (1964-1970)Third Generation computers (1964-1970)– integrated circuits,less heat, higher speed integrated circuits,less heat, higher speed

• Fourth Generation computers (1971-?)Fourth Generation computers (1971-?)– microprocessor microprocessor

•   Fifth Generation computersFifth Generation computers– 1981 – Personal Computer, PC1981 – Personal Computer, PC– Today - cheaper, smaller, better Today - cheaper, smaller, better – reasoning?reasoning?

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Computer Differences

• Microcomputers – pc– single user

• Minicomputer Systems– multiuser, typical - 20 terminals

• Mainframe

• Supercomputer

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Hardware• I/O and Storage Devices• Processor Unit

– CPU - central processing unit• brain – executes the instructions (program) stored in

memory• arithmetic logic unit (ALU) - operations and

computations• control section- executes instructions

– primary storage section - main memory • holds data and active program• RAM - random access memory

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Machine cycle

– Fetch • control unit fetches instruction from memory

– Decode • translate instruction into signals

– Execute• ALU performs operation

– Store

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Software

• System Software– Operating System - software that controls - software that controls

overall operation of computeroverall operation of computer

• Programming Environment• Editor• Compiler• Interpreter• Linker• debugger

• Applications Software

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Programming Language– Machine language

• binary coded instructions

• operation code - typical machine 50-200

• operand - data or address

• exa: 110011 - add instruction

– Assembly language • symbolic machine language

• low-level, machine dependent

• Requires assembler

• exa: ADD

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Assembly Language Exa:COMP$PAY PROC PUBLIC

;

; COMP$PAY - procedure to compute gross pay

; (PAY = HOURS * RATE)

MOV AX,HOURS ; multiplicand

MUL RATE+2 ; X second word of multiplier

MOV PAY+2,AX ; store the product in PAY

;

MOV AX,HOURS ; multiplicand

MUL RATE ; times first word of multiplier

ADD PAY+2,AX ; add the product to PAY

ADD PAY,DX ; add the carry, if any

RET ; end procedure

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programming language cont'd• high level

– machine independent – standardized

• official description of the language exists

– English-like– compiler - translates high-level language into machine

code– interpreted - examined one line at a time– portable

• separate compiler is required for each language on each computer

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Languages

• BASIC • FORTRAN • COBOL• PASCAL• C,C++• ADA• LISP• java

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Computer Science

• Science of information representation and management– Technology of computers– The way information is structured and managed

• Systematic study of those algorithms which describe and transform information: the underpinning theory, analysis, planning, efficiency, realization, and application

• Computer is the tool

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• Software engineering– Engineering– Project management– Personnel management– Programming language design

• Computer Architecture

• Artificial Intelligence

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technology

• Technology – externalizing human abilities into the things we make

• Paradigm – form or model evidencing a single theme or pattern– Paradigm shift

• Whole new ways of thinking emerge• New bodies of knowledge emerge• Chaos• Shift in power• Changes in the form of human expression

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The Computing Perspective

• Algorithmic conception of phenomena

• Simulation and experimentation

• Abstraction