CS 0004 –Lecture 1Wednesday, Jan 5th, 2011

Roxana Gheorghiu

My Office: 6414

Email: roxana@cs.pitt.edu

Web Page: www.cs.pitt.edu/~roxana/cs4

Class: Mon, Wed, Fri: 10:00am -10:50am

Office Hours (tentatively): Mon: 11:00am -1:00pm Wed: 11:00pm -1:00pm By appointment

Administrative Stuff

An Introduction to Computers

What are the main components of a computer

Processor (microprocessor, CPU –Central Processing Unit)

Memory (RAM –Random Access Memory)Hard Disk Drive (HDD)Several device cards: graphics card, sound card,

network card, modemInput/Output (I/O) Devices: keyboard, mouse;

monitor, printer

Hardware, Software and Servers

HardwareRefers to physical components of the computer Includes all components (even I/O)

SoftwareAll the programs written for a particular computer

or for any computers

Servers vs. Personal computerTerm “Personal computer” indicates that the

machine is operated by one person at a timeTerm “Server” indicates that the computer

provides resources to other computers

Make a computer understand

Language =any system of arbitrary signals such as voice sounds, gestures or written symbols

Computer languages classification Lowest level: Machine Code (binary) (110100100)Assembly language: symbolic representation of

Machine CodeHigh-level (Human –readable): Visual Basic, Java, C+

+It consists of instructions to which people can relate

(Click, if, do)

Ex: Try to speak with a French guy who doesn’t know English (assuming you don’t know French )

Communication protocolHuman-Readable to Machine-Readable

Compiler

110010010001011101010101001000101011010101010001010111010110101010010111100010101010110101001001001001

WindowsProgram

(.exe)

VBSource code

Private Sub Form_Load() MsgBox ("Hello, World!”)End Sub

Execute

Computer ProgramsA computer is a machine that does ONLY what it

is instructed to

Instructions are used in addition to language

The tasks are broken down into a sequence of instructions . This sequence is called a program

The process of executing the instructions is called running the program

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Make the robot leave the class and come back in the same position. Language: Move (#of stapes), Turn Left, Turn Right

What is a program?Collection of instructions that:

Accepts inputProcess DataOutputs results

Input OutputProcess

Why Visual Basic?Core of Microsoft Office Products

VBA (Visual Basic for Applications) allows us to “program” Excel

Allows you to make programs easilyLets you focus on problem at hand

Creates GUI’s not ugly command line

Interactive with user as an Event-Driven programming language

Event-driven programming paradigm

A way of designing a program: the application is driven by events

When creating an application, need to consider:How events can be (or should be) generated

creating an interface to accept actions from the user (e.g. button click)

How events are handledcoding event handlers to handle the events generated

Event-driven ProgrammingWhat is an event?

e.g. clicking a button, moving a mouse over a region, pressing a key, creating a form (window), timer going off

Something that happens in the program interface at a point in time (typically done by the user)

Event-driven ProgrammingWhat is an event handler?

A piece of code in our program that tells the program what to do when an event happense.g. when a particular button is clicked, update the display

How do events drive a program?Each event has a handlerWhen an event occurs, its handler is invoked If an event is not important, the programmer never writes an

event handler, so the program ignores the event

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Ex: click a button, text appear in my presentation. What is the event in this example ? What does the handler of

this event do ?