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

My Office: Web Page: 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, modem Input/Output (I/O) Devices: keyboard, mouse; monitor, printer

Hardware, Software and Servers Hardware Refers to physical components of the computer Includes all components (even I/O) Software All the programs written for a particular computer or for any computers Servers vs. Personal computer Term “Personal computer” indicates that the machine is operated by one person at a time Term “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) ( ) Assembly language: symbolic representation of Machine Code High-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 protocol Human-Readable to Machine-Readable Compiler Windows Program (.exe) VB Source code Private Sub Form_Load() MsgBox ("Hello, World!”) End Sub Execute

Computer Programs A 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 ************ 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 input Process Data Outputs results InputOutput Process

Why Visual Basic? Core of Microsoft Office Products VBA (Visual Basic for Applications) allows us to “program” Excel Allows you to make programs easily Lets 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 handled coding event handlers to handle the events generated

Event-driven Programming What 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 Programming What is an event handler? A piece of code in our program that tells the program what to do when an event happens e.g. when a particular button is clicked, update the display How do events drive a program? Each event has a handler When 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 *************** Ex: click a button, text appear in my presentation. What is the event in this example ? What does the handler of this event do ?