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A variable is a placeholder for a value. Variables are also stored in the programming for a memory location that is filled with a value. Variables need to be defined with a data-type, to define its storage space requirements. The name of the variable must start with a letter, but can it may contain numbers in within the wordname. In processing, variable names are case-sensitive.

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// variable Declaration 
int x1 = 15; // an integer i.e a whole number 
float valF = 0.323; // a floating point number i.e a numbers with a decimal point
boolean bFlag = false; // a true or false value i.e a single bit value
String message = "hallo 1"; // a collection of characters 
char character = 'g'; // a sigle character. Note the different quotation marks
 
String msg1 = new String("hallo 2");
 
println(x1);
println(valF);
println(bFlag);
println(message);
println(character);
println(msg1);

We can also makes make copies or combine variables. 

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An operator is a symbol that tells Processing the computer to perform a simple task, like for arithmetic and logic. particular arithmetic or logic operation. Some of the most common operators are:

+ Addition

/ Devision

- Subtraction

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These you already know but there are some very useful arithmetic operators you may not have seen in the following example .:

int x1 = 10;

x1++; // increment value by one 
x1--; // decrement value by one
 
x1 += 2; // Add assign, this is the same as writing x1 = x1+2; 
x1 -= 2; // Subtract assign, this is the same as writing x1 = x1-2; 
x1 /= 2; // Divide assign (less common), this is the same as writing x1 = x1/2; 

Exercise 2:

Take your results form from exercise 1 and modify your code to use variables. Create a variable X and variable Y that can be used to position your graphic on the screen.