02 programming concepts

8/3/2019 02 Programming Concepts

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Department of Computer Engineering, Faculty of Engineering, Chulalongkorn University

Programming Concepts

2140101 Computer Programming for International Engineers


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22140101 Computer Programming for International EngineersOPEN COURSEWARE MATERIALSCHULALONGKORNUNIVERSITY


Objectives

Students should: Know the steps required to create programs

using a programming language and related

terminology. Be familiar with the basic structure of a Javaprogram.

Be able to modify simple java to obtain desired

results


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Programming Languages

Program a set or sequence of instructionsthat tell a computer what to do

Instructions described using

programming languages

We execute a program to carry out theinstruction listed by that program.


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High-level Programming Languages

High-level programming languages:

rather natural for people to write.

Java, C, C++,

C#, VisualBasic, Pascal,Delphi,

FORTRAN,COBOL.


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Machine Languages

Machine language or object code:

Most primitive to the machines.

A set of binary code that is unique to the typeof CPU.

Each instruction = a fundamental operation ofthe CPU.

Writing object code directly is tedious and

error-prone.


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Machine Languages

Binary codesrepresented in

Hexadecimal formatMany instructions ofmachine code are

usually required forone line of high-levellanguage.


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Traditional Compiled Programs

Your Code

Compiler

(Windows)

Compiler(Linux)

Compiler(Mac OS)

executable file

executable file

executable file


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Running a Java Program


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Write once, run everywhere


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Programming Cycle


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First Java Program


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Look Inside a Program

MyFirstProgram.java

method

class


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Syntax, Keywords, & Identifiers

Syntax rules of the language, very strict

Keywords words that reserved for somepurpose. You cannot use keywords as an

identifier.

Identifiers names that given to classes,methods, and variables


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Java Keywords

whilesupernativefloatconst*

volatidestrictfplongfinallyclass

voidstaticinterfacefinalchar

tryshortintextendscatch

transientreturninstanceofenumcase

throwspublicimportelsebyte

throwprotectedimplementsdoublebit

thisprivateifdoboolean

synchroniz

edpackagegoto*defaultassert

switchnewforcontinueabstract

* not used


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Comments

Comments are ignored by the

compiler. They are used byprogrammers for:

Explaining the code.Making notes.

Other purposes.


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Comments

Block commentBlock comment

Single line commentSingle line comment


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Readability

Indentation and new lines are keys to

a high level of program readability.


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Readability

Imp

ro

vedre

adability


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On-screen Display


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println() andprint()

println() adds a new line afterdisplaying the message, whileprint() does not.

println() adds a new line afterdisplaying the message, whileprint() does not.


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Escape Sequences

An escape sequence is a special character sequencethat represents another character. Each of thesespecial character sequences starts with a backslash,which is followed by another character.


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Escape Sequences

\t Tab

\n Newline

\ double quote

\ single quote

\\ backslash


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D t t f C t E i i F lt f E i i Ch l l k U i it


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Naming Rules for Java Identifier

Cannot be a Java reserved word.

Case-sensitive

Unlimited length of sequence of Unicodeletters and digits

Must begin with a letter, underscore (_), ora dollar sign ($).

White space not allowed

Department of Computer Engineering Faculty of Engineering Chulalongkorn University


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Naming Convention

Use meaningful names

For compound words use camelCase.

Class names begin with an Uppercase letter.Account, DictionaryItem, FileUtility, Article

Variable names and method names begin with alowercase letter:

Height, speed, filename, tempInCelcius,imcomingMsg, textToShow.

(method names usually are verbs) locate, sortItem,findMinValue, checkForError

For a constant use all uppercase letters and underscore(_) to separate words in compound names.SOUND_SPEED, KM_PER_MILE, BLOCK_SIZE



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Expressions

An expression is a value, a variable, amethod, or one of their combinations that

can be evaluated to a value.3.875

a + b 10

8 >= xp || q

go

System.out.print(go)

Math.sqrt(2)

(x + 3 > y) && (x 3 < z)



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Statements

Complete sentence that causes some action to occur. ends with a semicolon (;)

int k;

int j = 10;

double d1, d2, d3;

k = a + b 10;

boolean p = (a >= b);

System.out.println(go);

sqareRootTwo = Math.sqrt(2);

block of statements are the statements withing a block of curlybraces ({ })

{

int m, n;m = 5;

n = m * m;

}



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Simple calculation

Arithmetic operators

add (+)

subtract (-)

multiply (*)

divide (/) modulo (%) : remainder after divide

Assignment operator (=) is used to assign

a value or the result from the calculationto a variable



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p p g g, y g g, g y

A Simple Calculation Program



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Another Calculation

Value of the variable avgValue of the variable avg

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