# Welcome to Computer Programming

 Variables Just like in math, variables are used to represent other things - numbers (integers, doubles, floats), text (characters, strings) and things (ie dogs by a dog class)   Need to declare what type it is in order to use it. We also need to give the variable a name: int weight; //so weight is the name and the type is int Dog myDog; Graphics g; All variables have a scope (global [everywhere], local [some places]- where it can be accessed from: We will return to this soon.   Remember We use camel case (with first lowercase) for variables that change; timeOfDay name things appropriately; for example studentAverage is much better than sA or s no spaces, cant start with number There are 2 types of variables: primitive - ints, doubles, boolean [there are others] - really basic stuff non-primitive - OBJECTS - Strings, Square, Cars, Graphics have methods and properties that can be done to them: like g.drawLine(23,23,40,40) and stringName.length() or square1.makeVisible() or bunny.move(50,frog); Primitive Types Integers (whole numbers + and -) - to declare a integer k and set its value as 50, we say ```int k; k=50; ``` or ```int k=50; ``` Now k has the value of 50; Or if we wanted to add 30 to what k was: ```k = k + 30; ``` If we wanted to add 1 to the value of i, we could ```i=i+1; ``` or shorter ```i++; ``` and if you wanted to decrease by 1 you could i--; We cant say:``` k=60.4;```   Another example: ``` int j=15/2;``` j would then be: 7 (not 7.5).   Doubles -used to store real numbers, numbers with decimals; like money: 75.67 or someones average 92.37 -to use, same as using an integer:   ```double studentAverage; studentAverage=92.37; ``` or ``` double studentAverage=92.37; ``` Boolean Booleans are variables that represent simply true or false. They can be very useful when all you want is a variable to be on or off, (true or false). The values true or false are not in quotation marks.   ```boolean firstTime = true; // the code below will be executed if firsttime is true // note it is not necessary to say firstTime ==true, although it will not give an error // if we wanted to do an if statment if it was false, we could say if (!firstTime) if (firstTime) { do this } ```