The Hello World example

This example is very basic. It illustrates the power of the ROOT system. Start the interactive version of ROOT and execute the two following commands:

Root >  TPaveLabel hello(0.2,0.4,0.8,0.6,"Hello World");
Root >  hello.Draw();

The first command creates an object of class TPaveLabel. The second command will draw this object and will automatically create a graphics canvas. The default canvas created by the Draw command has a default X and Y range defined between 0 and 1. The first 4 parameters in the first command are the lower and upper coordinates of the Pave.

You can now use the mouse and try the following:

• Move the mouse on the Pave and press the left button. Keeping the left button pressed, you can move the Pave in the Canvas.
• Point to one of the corners of the Pave and grow or shrink the Pave.
• Move the mouse on the Pave and press the right button. You get a context pop-up menu showing a list of possible actions. Try to change for example the text color.
• Same as above, but select the action Dump. This will print the actual parameters of the object hello on standard output.
• Make a Postscript copy of the canvas by selecting the option in the File menu at the top of the canvas.