For Beginner to PsychToolBox of Matlab (01)

1) Task_01: drawing a square of 100 x 100 pixels in the center of screen
任务01：画一个100x100像素的方块在屏幕中央

Tips:
using Screen() function. (get help by >> doc screen or >> help screen)
使用>> doc screen 或者 >> help screen 获取Screen() 函数帮助

open window -> draw window -> close window