James Tam

Introduction to software

Concepts covered

•What is software

•Categories of software and the differences between each

•The relation between software and hardware

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What is software?

The instructions that tell the hardware what to do.

1) Balance my check book.2) Do taxes3) Print out my resume4) : :

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Categories of software

• Application programs (applications)

• Operating systems

• Compilers

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Common types application programs

1) Word processors

2) Spreadsheets

3) Databases

4) Presentation software

5) Web browsers

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1) Word processors (e.g., MS-Word)

Lots of features (to be covered in lab)

•For text editing

•Images

•Customizable

•Built in Help

•And much, much more!

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2) Electronic spreadsheets (e.g., MS-Excel)

•Deals with rows and columns of numeric data

•Performs many calculations

•Many predefined mathematical functions (e.g., sum, average, min, max etc)

•Makes graphical representations of the data (e.g., graphs)

•Allows you perform a “what if” analysis

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3) Databases (e.g., MS-Access)

Allows data to be stored, organized, maintained and retrieved.

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4) Presentation software1 (e.g., PowerPoint)

Often used in presentations

The computer equivalent of transparencies

Allow for dynamic presentations (pictures, animations, sound) – can be overdone

1 It is listed in Beekman under the name “Presentation graphics”

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5) Web browsers

Internet Explorer

Netscape

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Operating systems: What do they do?

1) Act an an intermediary between the user and the hardware (mediator)

2) Manage the resources of the computer (parent)

3) Some may act to secure some parts of the computer (security)

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The operating system: The Intermediary between the user and the hardware

(operating system)

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Intermediary between the user and the hardware (e.g., hard drive)

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Manage system resources (parent)

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Manage system resources e.g., processor time

A = B + C

(Multi-tasking operating system)

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(Single tasking operating system)

A = B + C

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Manage system resources e.g., memory management

A = B + C

RAM

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Manage system resources (virtual memory)

A = B + C

RAM

Hard drive

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3) Securing information on the computer (security)

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Single user computer: security not a big issue

Mary

A2

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Multiple user system: there is a need to secure the information Separates and protects the work of different people who are working on a computer.

A2

Bill MaryGeorge

A2

A2

Bill’s A2

Mary’s A2

George’s A2

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Securing the information on the computer

This is not always done!

Single user operating systems don’t do this.

• MS-DOS, Windows 95, 98

Multi user operating systems do.

• Windows NT, Windows 2000, Windows XP, Unix

203 lab computers

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User Interfaces

Acts as the intermediary between the user and the software

Software (e.g., operating system)

User Interface

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Types of user interfaces

• GUI based

• Command line based

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GUI (Graphical user interface) based operating systems

Examples

•Windows (‘ 95, ’98, ME, NT, ‘2000, ‘XP)

•Apple (OS10)

Characteristics

•Many!

•Graphical (e.g., uses icons that are selectable with a mouse)

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Command line based software

Example

•Unix (Linux)

•MS-DOS

Characteristics

•Type in commands at a “command line”

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A WIMP(Window, Icon, Menu, Pointer)-based operating system: Windows

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An alternative to the desktop: Pad++

Pad++: A Zoomable Graphical Sketchpad for Exploring Alternate Interface Physics Bederson et al Journal of Visual Languages and Computing 7, 1996

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An alternative to WIMP: The task gallery

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Compilers (translators)

圣诞快乐和新年好 !

Huh?Merry

Christmas and Happy New

Year!

Same to you buddy!

Real life translation

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Compilers: translate between languages (high level view)

Do my taxes.

10001, 0001000, 100001…

The compiler

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Compilers: Actual view

1) A programmer writes a computer program 2) The compiler

translates the program into a form that the computer can understand

3) An executable program is created

Anybody who has this executable on their computer can then run (use) it.

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Relating software back to hardware: high level view of a computer (again)

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How does your computer look when it’s off?

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What happens when you turn on your computer (start-up): Step one execute instructions in BIOS.

To

From

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What happens when you turn on your computer (start-up): Step two load the operating system.

To

From

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At the desktop (OS running after start up)

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At the desktop (run an application with mouse): Step 1 Operating system interprets mouse information

???

???

What happened?

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At the desktop (run an application with mouse): Step 2 Operating system loads application

From

To

Application selected with mouse

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Summary (important points)

What is software

What are different categories of software

What are example types of application programs

What do operating systems do

How do compilers work

The relationship between hardware and software