TITLE
    Mac OS: Empty White Box On Screen
Article ID:
Created:
Modified: 		30556
5/29/98
3/20/01
TOPIC

    While using your Macintosh, an empty white dialog box with a ">" sign in the upper left-hand corner may appear. The box looks like an error message box, but there is no error message in it. This article describes the phenomenon and tells what to do when the box appears.

DISCUSSION

    The white box is the debugger window. It is also called the programmer's window. Certain buttons on old computers or key combinations on newer computers (all Power PC-based computers, for example) generate a special signal to the computer. This signal is called a "Non-Maskable Interrupt" or NMI. (An interrupt is a hardware signal that tells the computer to stop what it is doing and devote its attention to a more important task.)

    Note: Typing "g" or "g Finder" will dismiss the empty box if it was entered on purpose.

    The default key combination which causes the box to appear is "Command-Power". The power key is the key in the upper right hand corner of an Apple Extended Keyboard or an Apple Design Keyboard. It is also called the Reset key. This key has an icon that looks like a triangle pointing to the left. The switch is also called the debugger switch, the interrupt switch or the programmer's switch.

    Also, if the Command key or Power key is stuck (or the computer thinks it is stuck), typing the other of the two keys may cause this to appear. Use Key Caps to see if a key is stuck down.

    Note: The Power key may not actually turn the computer on.

    If you have a debugger installed (such as Apple Computer's MacsBug), you may get a more elaborate screen with low-level information about how the computer's memory is being used. This information is useful only to someone with a knowledge of assembly language programming and Mac OS Memory Management.

    To exit MacsBug, try the following steps:

    1. Type "g" and Return. If MacsBug was entered on purpose, either by the user or some debugging code in a program, you should be able to continue.

    2. If the MacsBug screen comes right back, Type "es" and return. This is roughly equivalent to force quitting the current application. If this works, save your work in your open applications and restart the computer.

    3. If the above steps fail, you can type "rs" or "rb" to restart your computer. All unsaved work is lost.

    4. If none of the above options work, press Command-Control-Power or toggle the power switch to restart your computer. All unsaved work is lost.

    Once the computer is no longer in MacsBug, you may remove it from the System Folder by dragging MacsBug out of the System Folder and restarting the computer.

    Note: MacsBug is a developer tool, and is not supported by Apple telephone technical support. However, MacsBugs is available for download from:

    ftp://dev.apple.com/devworld/Tool_Chest/Testing_-_Debugging/Debuggers_-_dcmds/

Document Information
Product Area: Apple Software
Category: Mac OS Error Codes & Messages
Sub Category: General Topics
Keywords:

Copyright © 2000 Apple Computer, Inc. All rights reserved.