Understanding Pseudocode for Problem Solving in JavaScript - Prof. Nelson Padua-Perez, Assignments of Computer Science

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Announcements

 Instructor: Nelson Padua-Perez ([email protected])

 No posting of code in the forum

 Check class announcements daily

 You must implement programming projects by yourself

Designing Using Pseudocode

 So far we have focused on the syntax and semantics of JavaScript  As the complexity of problems increase you need a design strategy to solve such problems  Several alternatives exist to come up with a solution to a problem. A popular one is Pseudocode

Pseudocode: English-like description of the set of steps required to solve a problem

 When you write pseudocode you focus on determining the steps necessary to solve a problem without worrying about programming language syntax issues

Pseudocode Elements

 When writing pseudocode you need the following constructs:  Input  Output  Assignments  Repetition Structures  Conditionals  To help you with the design of pseudocode you can use the following syntax to represent the above constructs

Pseudocode Elements

 Input variable = read() e.g., x = read()  Output print(variable) e.g., print(x)  Assignment x = e.g., x = 20, s = “Bob”  Repetition while (expression) { OR do { stmts stmts } } while (expression)

 Notice the above constructs look like JavaScript code but they are not JavaScript code

How Good Is Your Pseudocode

 Your code does not use language constructs that are particular to a programming language

 Anyone receiving the pseudocode will not need to ask you questions in order to transform the pseudocode into code (no matter what the target programming language is)

do while Statement

 do while statement – Allows repetition of a set of statements

Basic Form do { statement // executed as long as expression is true

} while (expression) ;

 Notice the semicolon after the expression in parenthesis  Executes the statement at least once  You don’t need the { } if you only need to execute one statement  Example: DoWhileNumbers.html  Example: DoWhile.html  Any type of statements (including do whiles) in a do while  When to use a do while?  When to use a while?

Creating a Bookmark in a Document

 Use name attribute to define the target

 Use to jump to location

Web Site Snapshot/Video

 Online Example: http://www.cs.umd.edu/class/spring2009/cmsc122/projects/p2/p2Description.html#Sample_Output

Coding Example

 Let’s write a program that reads a password and allows a maximum of two attempts

 We can expand the program to have a menu of options once the appropriate password has been provided

 Using “\n” to define menu entries