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The Effects of Computers • • • • Pervasive in all professions How have computers affected my life? Internet Computer Literacy – knowing how to use the computer – knowing capabilities and limits computer system overview 1 History of Computers • First Generation computers (1951-1958) – vacuum tubes – used large amounts of electricity, heat – large and expensive – 1946 - ENIAC - computed trajectories for U.S. Army – 1951 - UNIVAC - first commercially available computer computer system overview 2 • Second Generation computers (1959-1963) – Transistors,less heat,more reliable, less expensive • Third Generation computers (1964-1970) – integrated circuits,less heat, higher speed • Fourth Generation computers (1971-?) – microprocessor • Fifth Generation computers – 1981 – Personal Computer, PC – Today - cheaper, smaller, better – reasoning? computer system overview 3 Computer Differences • Microcomputers – pc – single user • Minicomputer Systems – multiuser, typical - 20 terminals • Mainframe • Supercomputer computer system overview 4 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 computer system overview 5 Machine cycle – Fetch • control unit fetches instruction from memory – Decode • translate instruction into signals – Execute • ALU performs operation – Store computer system overview 6 Software • System Software – Operating System - software that controls overall operation of computer • Programming Environment • • • • • Editor Compiler Interpreter Linker debugger • Applications Software computer system overview 7 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 computer system overview 8 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 computer system overview 9 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 computer system overview 10 Languages • • • • • • • • BASIC FORTRAN COBOL PASCAL C,C++ ADA LISP java computer system overview 11 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 computer system overview 12 • Software engineering – – – – Engineering Project management Personnel management Programming language design • Computer Architecture • Artificial Intelligence computer system overview 13 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 computer system overview 14 The Computing Perspective • Algorithmic conception of phenomena • Simulation and experimentation • Abstraction computer system overview 15