Chapter 10 Programming Fundamentals with Java Script Computers

Chapter 10 Programming Fundamentals with Java. Script “Computers and Creativity” Richard D. Webster, COSC 109 Instructor Office: 7800 York Road, Room 422 | Phone: (410) 704 -2424 e-mail: webster@towson. edu 109 website: https: //tigerweb. towson. edu/webster/109/i 1

In this lecture, you will learn: • the differences between programming languages and scripting languages • programming concepts and constructs: syntax, data types, variables, statements, assignment statements, operators, constants, keywords, expressions 2

Coding • Writing code – means entering the code – is part of the process of creating the computer program • Run, running, execution – refers to the process by which the computer carries out the instructions in a computer program • Compiling, compilation – refers to the process of assembling code into a format suitable for the computer to execute the instructions 3

IDE • stands for: Integrated Development Environment • refers to: – the software in which you are developing an application – for example, Adobe Animate, Microsoft Visual Studio 4

Programming Languages Multimedia authoring scripting languages, such as Java. Script and Animate Actionscript are often the highest level. high level Programming languages that look more like human language. Easy for human to read and write, but require more "translation" behind the scenes to be understandable to the computer. e. g. C++, C#, Java, FORTRAN Assembly language low level lowest level: Machine language: a programming language that communicates with a computer through 0's and 1's 5

Scripting Languages • Examples: Javascript and Animate Action. Script • Very-high-level programming languages • Advantage: easier for non-programmer to learn because the syntax and keywords are close to human languages • Disadvantages: – Not as full-fledged as programming languages such as C++, Java, and FORTRAN – Don't have the features to let the programmer to control low level details, such as memory allocation 6

Java. Script Syntax • prescribes the ways in which statements must be written in order for them to be understood by the computer • like the rules of grammar and punctuation in human languages, but these rules must be followed precisely in computer programming • for examples, for Java. Script: – case sensitive – each statement ends with a semi-colon(; ) – the naming of variables and functions has to start with a letter , _ or $ 7

Basic Programming Constructs syntax variables statements assignment statements • keywords • operators • expressions • • • procedures functions arguments control structures conditions comments arrays loops In this Powerpoint 8

Variables • Purpose: to store values that can be updated and retrieved at runtime • Data is stored in memory as bits. • Variable lets you refer, by name, to the data's memory location stored. • has 3 Properties: – Name: Code refers to memory location by name – Value: The actual information stored at the location – Type: The particular type of data (data type) Examples: integer, floating point, string 9

Loose vs. Strict Data Typing • Strict data typing – When a programming language requires that you explicitly declare the data type of a variable when the variable is first created • Loose data typing – When a programming language does not have such data typing requirement. – Java. Script is loosely typed language 10

Variable Naming • can contain a number, a letter, underscore (_), or dollar sign ($) • cannot begin with a number • in this course, variables always begin with a letter • must not contain spaces • cannot be a keyword • score and Score are different • number and nu. MBer are different 11

Variable Naming Which are valid variable names? • my. Score • my_score <- This one ; -) • my score • my-score • my 4 score • 4 score 12

Assigning a Value to a Variable • Means giving a value to a variable • The statement that assigns a value to a variable is called an assignment statement. • General Syntax: variable. Name = value or expression; • Examples: score = 10; letter. Grade = "A"; sum = a + b; 13

Statements • Statements are instructions that can be executed • A statement ends with a semi-colon (; ) when there are more than one statements on the same line • Purposes: For examples, – to give values to variables (assignment statements) – to cause things to happen only under certain conditions (e. g. if-statements) – to cause instructions to repeat (used in loops) 14

Operators • symbols that cause a new value to be calculated from one or more other values • Examples: – arithmetic: +, -, *, /, % give new calculated values – comparison operators: >, >=, <, <=, ==, != give a value of true or false – logical operators: &&, ||, ! give a value of true or false 15

Assignment Operators =, +=, -=, *=, /=, %= score score += -= *= /= %= 3; 3; 3; score score = = = score score + – * / % 3; 3; 3; 16

Assignment Operators =, +=, -=, *=, /=, %= score = 10; score += 5; What is the value for score after these two statements? 17

Assignment Operators =, +=, -=, *=, /=, %= score = 10; score *= 2; What is the value for score after these two statements? 18

Keywords • Reserved words that have a special meaning in a programming language. • You are not allowed to use these words for any other purpose, such as variable or function names. • Examples: var if for function true false 19

How a Program Runs • A program is written as a sequence of statements as instructions. • The program executes the instructions sequentially--one instruction after the other, in the order in which they appear in the code. • Use control structures to make nonsequential execution of the instructions. 20

Types of Control Structures • Loop – A set of statements is executed repeatedly until a certain condition is reached – Will be covered in Chapter 11 • Conditional – A set of statements is executed only if some conditions are met – if statements and switch statements 21

if Statements • • if if. . . else if Nested if statements 22

if General Syntax: if (logical expression(s)) { statement(s) } The statements grouped within the curly braces are called the block statements. 23

if • If there is only one statement to be executed, the curly braces are optional. • Examples: if (score > 60) grade = "pass"; The statement may be on a single line: if (score > 60) grade = "pass"; 24

if. . . else General Syntax: if (logical expression(s)) { statement(s) } else { statement(s) } 25

if. . . else Example: if (score > 60) { grade = "pass"; } else { grade = "fail"; } 26

if. . . else if General Syntax: if (logical expression(s)) { statement(s) } else if (logical expression(s)) { statement(s) }. . . else if (logical expression(s)) { statement(s) } else { statement(s) } 27

if. . . else if Example: if (score > 90) { grade = "A"; } else if (score > 80) { grade = "B"; } else if (score > 70) { grade = "C"; } else if (score > 60) { grade = "D"; } else { grade = "F"; } 28

if. . . else if • The conditions are checked one at a time sequentially. • Once a condition is found to be true, the statement(s) for that condition will be executed and the rest of the conditions in the if. . . else if statements group will not be checked. 29

if. . . else if Example: if (score > 90) { grade = "A"; } else if (score > 80) { grade = "B"; } else if (score > 70) { grade = "C"; } else if (score > 60) { grade = "D"; } else { grade = "F"; } Suppose score = 85. 30

if. . . else if Example: if (score > 90) { grade = "A"; } else if (score > 80) { grade = "B"; } else if (score > 70) { grade = "C"; } else if (score > 60) { grade = "D"; } else { grade = "F"; } Suppose score = 85. First check: (score > 90). (85 > 90) is false! 31

Logical Operators && AND || OR ! NOT 32

Logical AND: && logical. Expression 1 && logical. Expression 2 true : only when both logical. Expression 1 and logical. Expression 2 are true false : when either logical. Expression 1 or logical. Expression 2 is false 33

Logical OR: || logical. Expression 1 || logical. Expression 2 true : when either logical. Expression 1 or logical. Expression 2 is true false : only when both logical. Expression 1 and logical. Expression 2 is false 34

Logical NOT: ! !logical. Expression 1 true : when logical. Expression 1 is false : when logical. Expression 1 is true 35

Examples Example 1 if (age < 40 && weight < 150) { group = 2; } else { group = 3; } Example 2 if (age < 40 || weight < 150) { group = 2; } else { group = 3; } Which statement will be executed in these examples when age = 38 and weight = 145? 36

Examples Example 1 if (age < 40 && weight < 150) { group = 2; } else { group = 3; } Example 2 if (age < 40 || weight < 150) { group = 2; } else { group = 3; } Which statement will be executed in these examples when age = 38 and weight = 157? 37

Examples Example 1 if (age < 40 && weight < 150) { group = 2; } else { group = 3; } Example 2 if (age < 40 || weight < 150) { group = 2; } else { group = 3; } Which statement will be executed in these examples when age = 46 and weight = 145? 38

Examples Example 1 if (age < 40 && weight < 150) { group = 2; } else { group = 3; } Example 2 if (age < 40 || weight < 150) { group = 2; } else { group = 3; } Which statement will be executed in these examples when age = 46 and weight = 157? 39

Review • A function or procedure contains a block of program instructions forming a discrete unit with a name. • Functions are executed only when called within the program. Functions do not execute automatically. • Functions return a value to a calling statement whereas procedures do not. © 2016 Pearson Education, Inc. , Hoboken, NJ. All rights reserved. 40

Review • Values passed into functions or procedures are known as arguments. • The type of a value is known as a data type. • Variables are used to store values. Those variables can change during a program’s operation. • If statements and loops can be used to make programs execute sequentially. © 2016 Pearson Education, Inc. , Hoboken, NJ. All rights reserved. 41

Review • Action. Script is a strictly typed language and is case-sensitive. • Statements in Action. Script end with a semicolon (; ) • An example of a valid variable name in Action. Script would be: my_score © 2016 Pearson Education, Inc. , Hoboken, NJ. All rights reserved. 42