Download Computer Science

The Effects of Computers
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Pervasive in all professions
How have computers affected my life?
Internet
Computer Literacy
– knowing how to use the computer
– knowing capabilities and limits
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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
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• 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?
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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 overall
operation of computer
• Programming Environment
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Editor
Compiler
Interpreter
Linker
debugger
• Applications Software
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Programming Language
– Machine language
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binary coded instructions
operation code - typical machine 50-200
operand - data or address
exa: 110011 - add instruction
– Assembly language
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symbolic machine language
low-level, machine dependent
Requires assembler
exa: ADD
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Assembly Language Exa:
COMP$PAY
PROC PUBLIC
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; COMP$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
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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
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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
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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
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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
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