Programming Methodology - Introduction to Computing - Lecture Slides, Slides of Introduction to Computing

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CS101 Introduction to Computing

Lecture 44

Programming Methodology

(Web Development Lecture 15)

During the last lecture we discussed Graphics & Animation

• We became able to add and manipulate images and simple animations to a Web page

Images in JavaScript

• Images in JavaScript can be manipulated in many ways using the built-in object, Image
• Properties: name, border, complete, height, width, hspace, vspace, lowsrc, src
• Methods: None
• Event handlers: onAbort, onError, onLoad, etc.

Image Preloading

• The primary use for an Image object is to download an image into the cache before it is actually needed for display
• This technique can be used to create smooth animations or to display one of several images based on the requirement

Animated Gifs

• We could have saved the 16 gif images of the previous example in a single file in the form of an animated gif, and then used it in a regular tag to display a moving image
• However, JavaScript provides better control over the sequencing and the gap between the individual images
• Example

Today’s Goals (Programming Methodology)

• To understand effective programming practices that result in the development of correct programs with minimum effort
• To become familiar with testing & debugging

programming

methodology?

10

good A methodology that enables the lowest-cost and on- schedule development of programs that are correct, easy to maintain & enhance

correct

program?

11

A program with correct syntax & semantics

13

swapFlag = true ;

while ( swapFlag == true ) {

swapFlag = false ; for ( k = 0 ; k < ht.length - 1 ; k++ ) { if ( ht[ k ] < ht[ k + 1 ] ) { temp = ht[ k + 1 ] ; ht[ k + 1 ] = ht[ k ] ; ht[ k ] = temp ; swapFlag = true ; } }

}

How can we make it more readable? What is its most complex aspect?

Bubble Sort

14

for ( j = 0 ; j < 100000 ; j++ ) {

for ( k = 0 ; k < ht.length - 1 ; k++ ) { if ( ht[ k ] < ht[ k + 1 ] ) { temp = ht[ k + 1 ] ; ht[ k + 1 ] = ht[ k ] ; ht[ k ] = temp ;

} Docsity.com

guidelines

Design Guidelines

• Break your code down into short and simple functions (e.g. take the 3 swap statements out from the last example and put them into a function of their own)
• Do not use global variables

Comments let the

code speak for

itself!

Guidelines for Developing Short Programs

1. Read, understand the problem
2. Do you have all the required data?

No: Get it Else assume it. State it explicitly