CS 127Introduction to Computer Science

What is a computer?

“A machine that stores and manipulates information under the control of a changeable program” [1]

“A computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations” [2]

Two key concepts:It is a machineIt can be controlled via instructions[1] Python Programming : An Introduction to Computer Science - Zelle[2] Wikipedia

What is a computer program?

“Detailed step by step instructions telling a computer exactly what to do” [1]

“It is a sequence of instructions, written to perform a specified task with a computer” [2]

Computers simply execute programs or instructions

Without being told what to do, computers would not be useful

Software (programs) rules or controls the hardware (physical machine)[1] Python Programming : An Introduction to Computer Science - Zelle[2] Wikipedia

Programming

The process of creating softwareIt is a challenging

You have to see the big pictureYou have to pay attention to every detail

It is important to learn programming because it is such an integral part of computer science

Allows development of problem solving skillsAllows complex systems to be analyzed and

reduced to interactions and understandable subsystems

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What is computer science?

“The scientific and practical approach to computation and its applications” [1]

Computers are simply a tool that are used in computer science

Three important conceptsDesignAnalysisExperimentation

5[1] Wikipedia

Design

Formulating a solution to a problemOften involves a step by step process for

achieving a resultAn algorithm

Look at problems in a logical way and design a solution

This is a critical process in computer science

Most time should be spent here to allow for efficiency in the development process 6

Analysis

The process of examining algorithms and problems mathematically

Every algorithm to solve a problem cannot always be implementedLack of computational resourcesNot feasible time-wiseNot enough memory

Analysis of algorithms is important in computer science

The bottom line is whether a working, reliable system can be built 7

Other areas of computer scienceNetworkingHuman-Computer InteractionArtificial IntelligenceComputational Science (using

computers to model scientific data)DatabasesSoftware EngineeringWeb and Multimedia DesignMIS (Management Information Systems)Security 8

Computer Hardware

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Computer Hardware

Central Processing Unit (CPU) - Brain of the computer

Memory - Stores programs and dataMain Memory (RAM - Random

Access Memory)RAM - Fast and VolatileCache

Secondary Memory or StorageHard Disk DriveOptical Drive - CD, DVD 10

Computer Hardware

Peripheral DevicesKeyboard - InputMouse - InputMonitor - OutputPrinter - Output

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Computer Hardware

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Programming Languages

Computers need to be told in explicit terms what actions they must perform

Languages that computers can understand need to be precise and exact

Every structure in a programming language has a precise form (syntax) and a precise meaning (semantics)

Programs are often referred to as computer code and the process of writing an algorithm in a programming language is called coding 13

Programming

Programming languages are considered “higher level” languages

Computer hardware can only understand “low-level” languages referred to as “machine language”

Computers understand binary (1s and 0s)

A higher level language is converted into a lower level language by:CompilationInterpretation 14

Compiler vs Interpreter

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Compiler Interpreter

Takes high level source code and converts it into low level machine code

Analyzes and executes source code instruction by instruction

Once program is compiled, it can be run multiple times without needing the compiler and source code

Interpreter and source needed every time the program is run

Compiled programs are generally faster

Interpreted programs are more flexible as you can develop and run programs interactively

Portability

Machine language is specific to a particular CPU

Each kind of computer has its own machine language

Programs written in a high level language can be run on different computers as long as a compiler and interpreter exists for that computer

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Python

It is an interpreted languageSimple yet powerful and robustGood initial language to learn

programmingCompanies that use Python

GoogleYahooDisneyIBMNASA 17

Running Python programs

IDLE GUICommand line InterpreterGood resource

http://www.python.org/doc/

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