REVIEW & WRAP-UP of Introduction to Computing

<< PROGRAMMING METHODOLOGY

Introduction to Computing CS101

LESSON 45

REVIEW & WRAP-UP

During the last Lesson we discussed Programming Methodology

We looked at a few effective programming practices that result in the development of correct

programs with minimum effort

We also became familiar with testing & debugging

readable

program?

A program that is easy to read &

understand, and therefore, easy to

maintain & enhance

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

Coding Guidelines

Indent blocks of code (2 to 5 spaces)

Always use semicolons to end statements

Identifiers:

Use the camelBack scheme

Make them descriptive but concise

Variables: nouns

Functions: verbs

Comment liberally

Guidelines for Developing Short Programs

Read, understand the

problem

Write the code on a piece of

paper

Do you have all the

required data?

Hand-check it

No: Get it

Type it in

Else assume it. State it

Run & check it on test cases

explicitly

Errors? fix & redo 9

Do the design

Done!

Write test cases

Design & Code Reviews

Probably the most efficient way of improving the a program

Being humans, at time we see what is supposed to be there instead of what is actually there

Another pair of eyeballs may not have the same problem, especially if they are were not involved

in building the design or code

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Testing & Debugging

Testing: The tasks performed to determine the existence of defects

Debugging: The tasks performed to detect the exact location of defects

Defects are also called bugs or errors

Let us now look at one of their classifications

Types of Errors

Syntax errors

Semantic errors

Run-time errors

Today's Goal:

(Review & Wrap-Up)

To review some of the interesting ideas that we discussed over the last 44 lectures

Please note that this lectures is not a comprehensive review, just a sampler!

Course Objectives

To build an appreciation for the fundamental concepts in

computing

To achieve a beginners proficiency in Web page development

To become familiar with popular PC productivity software

Progression of Computer Technology

Mechanical computing

Electro-mechanical

Vacuum tube

Transistor

(the current state-of the-art)

Quantum computing

Quantum Computers

Quantum computers may one day be millions of times more efficient than the current state-of-the-

art computers ...

as their quantum mechanical nature will allow them to examine all possible answers to a question,

simultaneously

The World Wide Web

A huge resource of info

Logically unified, but physically distributed

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It is unlike any previous human invention:

It is a world-wide resource, important to all and shared by all of the people in the world

The Semantic Web

Whereas, today's Web's content is designed for humans to read; the Semantic Web's content will be

designed for computers to understand meaningfully

Internet: Network of Networks

A large number of networks, interconnected physically

Capable of communicating and sharing data with each other

From the user's point view, Internet a collection of interconnected networks looks like a single,

unified network

Language of the Internet: TCP/IP

Transmission Control Protocol/Internet Protocol

TCP breaks down the message to be sent over the Internet into packets

IP routes these packets through the Internet to get them to their destination

When the packets reach the destination computer, TCP reassembles them into the original message

Instant Messaging

eMail: Slow response times

eMail: No way of knowing if the person we are sending eMail to is there to read it

eMail: The process of having a conversation through eMail by exchanging several short messages

is too cumbersome

Instant messaging (IM) solves these problems

On-Chip Cache Memory

That small amount of memory located on the same chip as the uP

The uP stores a copy of frequently used data and instructions in its cache memory

When the uP desires to look at a piece of data, it checks in the cache first. If it is not there, only

then the uP gets it from the main memory

Its proximity to the uP makes access times short

Ways of Enhancing A uP

Increase the clock frequency

Increase the word-width

Add more functional units (e.g. ALU's, FPU's, Vector/SIMD units, etc.)

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Hardware

Operating System

Device Driver

Utilit

Language

Scientific

Business

Productivit

Entertainment

Translator

Apps.

System software

Application software

The Role of An OS

Manages the HW and SW resources of the computer system, often invisibly. These include the

processor, memory, disk drives, etc.

Provides a simple, consistent way for applications to interact with the HW without having to know

all the details of the HW

Who Owns Software?

Generally, although a piece of SW that is being used by millions, it is not owned by any of them!

When we buy a SW package, we do not really buy it we just buy a license that allows us to use it,

the ownership stays with the maker

4th-generation languages

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Machine languages

Interpreters:

Immediate response, but execute code slowly

Compilers: Compiling takes time, but super-fast execution

High-level languages

Assembly languages

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Concept &

Feasibility

Test

User Requirements

Developer Specs

Test

Planning

Test

Design

Test

Implementatio

Integration

Testing

Acceptance

Opr. &

Test

Maintenance

Retirement

Algorithm

1st Definition:

Sequence of steps that is taken

to solve a problem

Better Definition:

A precise sequence of a limited

number of unambiguous, executable

steps that terminates in

the form of a solution

Pseudo Code

Quite suitable for SW development as it is closer in form to real code

One can write the pseudo code, then use it as a starting point or outline for writing real code

Many developers write the pseudo code first and then incrementally convert each line into real

code

Heuristic

Common sense Lesson drawn from experience

(Artificial) Intelligent Systems

SW programs or SW/HW systems designed to perform complex tasks employing strategies that mimic

some aspect of human thought

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Not a Suitable Hammer for All Nails!

if the nature of computations required in a task is not well understood

or there are too many exceptions to the

rules

or known algorithms are too complex or inefficient

then artificial intelligent systems have the potential of offering an acceptable solution

Database

A collection of data organized in such a fashion that the computer can quickly search for a desired

data item

All data items in it are generally related to each other and share a single domain

Relational Databases

Databases consisting of two or more related tables are called relational databases

A relational database stores all its data inside tables, and nowhere else

All operations on data are done on those tables or those that are generated by table operations

Future Trends:

On-Demand Computing Power

Almost infinite "computing power" supply

Reliable, maintenance-free, just like the electricity, telephone, or water-supply service

No capital expenditure; you pay for only what you use!

Same will be true for storage

Future Trends: Immortal Minds

Some day it will be possible to load all the lectures, papers, books and SW produced by an expert

into an intelligent system

After that system processes, indexes and restructures the info in those artifacts, it will be possible

to have a conversation in plain English (or some other language) with that system

Distances Are Contracting!

Distances Are Increasing!

Because of the ever-decreasing costs of verbal, text, video communications, it is becoming easier to

stay in touch of anyone, regardless of their physical location

Solitude is the order of the day as many children & adults spend their free time surfing, chatting,

playing computer games, instead of spending it on interacting with friends or family

Computers may Become too Powerful!

Computers keep on becoming more and more powerful, gaining more and more autonomy

They are being equipped with fail-safe and self-healing technologies

Are we heading towards a future where the role of the masters and the slaves will be reversed?

Why JavaScript?

HTML is great for static Web pages; however, supports only rudimentary interactivity through

forms and hyperlinks

JavaScript can be used (along with HTML) to develop interactive content for the Web

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Some of things that JavaScript cannot do!

The following file ops. on the client computer:

Read

-- Modify

Rename

-- Delete

Create

Create graphics (although, it does have the ability to format pages through HTML - including the

placement of graphics)

Any network programming bar one function: the ability to download a file to the browser specified

through an arbitrary URL

Advantages of Client-Side Scripting

Reduced server load as it does not have to send messages to the user's browser about missing or

incorrect data

Reduced network traffic as the form's data is sent only once instead of many to's and fro's

A collection of

properties &

methods

All objects have the

"name" property: it holds

the name of the object

(collection)

prop 1

method 2

prop 2

prop 5

prop 3

method 1

method 3

prop 4

Object: A named collection of properties (data, state) & methods (instructions, behavior)

Functions

A named group of statements that is put together once and then used (by reference) repeatedly on a

Web page

Code becomes easier to read, understand and maintain

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Local and Global Variables

Local or Function-level Variable

Effective only in the function in which they are declared

Global Variables

Visible everywhere on the Web page

Image Preloading

The Image object can be used 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

Productivity SW

The lectures and assignments were designed to give a brief introduction, and no more

All we desired was for you to become able to open the package and perform some trivial tasks

With time, you will find more and more use for these packages, and gradually develop an expertise

that later will become very useful in your career

Course Objectives

To build an appreciation for the fundamental concepts in computing

To achieve a beginners proficiency in Web page development

To become familiar with popular PC productivity software

How successful were we in helping you achieve those objectives?

Please do let us know so that we can modify the future offerings of this course accordingly. I will

be most grateful

I have enjoyed doing this course with you very much

Hope it was enjoyable & useful for you as well

I thank you for your attention and especially for your eMail & discussion board messages

A good number of those messages were quite informative and I thank you for sharing that info with

Until the next time when we meet ...

********************THE END*******************

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