Code Elements and Processing Coordinate System

Code elements: pages Comments: are documentation notes that are ignored by the computer but are important for people (to understand the code). // single line comment /* multi line comment */ Semi-colon (“;” ) is a terminator Example: size (600, 600);

Functions Functions are pre-defined operations You can define the functions or use the functions already defined and available in libraries/packages Functions promote modular design Example: size(500,500); background(102); Function call parameters

Expressions Expression are means for expressing a computation or logic Example: value is > 90 value is false

Variables and types Variables represent items in the problem to be solved Variables have (i) type (ii) name by which they are referenced in the code Example: int age; float wage; char initial; We will discuss variables in more detail later.

Console and Printing Messages Processing has two instructions for printing out on console: print(…) and println(..) These can be used to display data when a Processing code is running Good instructions for understanding your code and trace what is happening with the code. Good “debugging” tool. Example: (see p.21) int x = 20; println(x); int x2 = 20; int y2 = 30; println(x2 + “ “ + y2); println(“I am learning Problem solving using Processing”);

Coordinates and Primitives Before you “draw” you need to think about dimensions and qualities of the surface on which you’ll be drawing. Computer monitor have surfaces that are defined by “pixels” or a “picture element” When the definition of the screen of your laptop is 1280 X 1024 that means you have 1,310,720 little pixels to display your content on the screen In processing when you say “size (200, 100)” we have width of 200 pixels and height of 100 pixels

Processing Coordinate System (10X10) X  0,0 Y  10,10

Primitive Shapes point(x,y) Example: point(2, 67); line(x1,y1, x2, y2) Example: line(23,45, 56,90); triangle(x1,y1,x2,y2,x3,y3); Example: triangle(60,10,25,60,75,65);

More Primitive Shapes quad(20,20,20,70,60,90,60,40); quad(20,20,70,-20,110,0,60,40); Quad is specified using points Rect function uses starting point and lengths rect(x, y, width, height); ellispe(x,y,width,height); // is used for drawing circle

Complete example Lets draw a desktop computer. rect(0, 0, 90, 50); rect(5, 50, 75,4); rect(24, 54, 6,6); rect(64,54, 6, 6); rect(20, 60, 75, 10); rect(10, 70, 80, 2);

Drawing attributes fill(r,g,b); Before you draw will fill the object you draw with the fill color. smooth(); noSmooth(); strokeWidth(6); noStroke(); Lets try these commands on Processing