Same as another smart handphone, Blackberry have many code that used for reset, restart blackberry without release battery, format memory blackberry, multitasking, etc.
Many codes are :

• Left SHIFT + Right ALT + DEL : master reset Blackberry, Press & Hold them until LCD swithed off and red blinking LED. Remember, all your data in the phone will be lost..
• ALT + Right SHIFT + DEL : Restart blackberry without release the battery, that functioned t refresh memory or to configure after installing an application.
• On home screen, press ALT and follow ‘LGLG‘, event log displayed. After that step you can press HOME and choose CLEAR LOG. This code fonctioned to clear Log.
• Same as your PC, you can jump to the other application. ALT + TAB n your PC, on Blackberry press ALT + ESC.

All in your own risk, I’m only give what I know. Good Luck & Wassalam.