Macintosh System Error Codes Explained
This article explains what some Macintosh
system errors actually mean. You can use them to interpret what
is happening when your Macintosh gives these errors.
Because the Mac OS
is a sophisticated, complex operating system, the problems a user
encounters can be equally complex.
These are examples of some problems that may occur:
- A handle can be de-referenced.
- A routine can get a NIL
- The stack can dip into
the heap for just a few cycles and not be caught by the stack
- An application can forget
to check an error code.
A Macintosh usually crashes with a system error code while running
under System 6.0.x. Starting with System 7, errors are displayed
in a different fashion. Instead of displaying an error code, the
system translates the code to the appropriate words, like "Address
Finding out what's wrong involves use of debugging tools, intricate
knowledge of Macintosh memory structures, and familiarity with the
application itself. Fixing it usually involves recompiling the source
code. The table below explains some of the codes.
ID=01 Bus Error
This means the computer tried to access memory that doesn't exist.
You can get this error on almost any Macintosh. If one of these
computers tried to access one or more bytes beyond the total number
of bytes in RAM, you see a bus error. You should never see this
error on a Macintosh Plus or SE, because address references that
are out of bounds "roll over". This means if one of these
computers tries to access one byte beyond the total bytes in RAM,
it actually accesses the first byte in memory. If you see this error
on a Macintosh Plus or SE, it's reporting the wrong error or having
ID=02 Address Error
The Motorola 68000 microprocessor can access memory in increments
of one byte (8 bits), one word (16 bits), or one long word (32 bits).
The microprocessor can access a byte of information at an odd or
even memory address. But it must access a word or long word at an
even memory address. So, when the microprocessor attempts to read
or write a word or long word at an odd address, you see this error.
Since that's a 50/50 proposition when running random code, this
one shows up quite often.
ID=03 Illegal Instruction
The computer has a specific vocabulary of machine language instructions
it can understand. If a computer tries to execute an instruction
that isn't in its vocabulary, you see this error code. It's less
likely than error 02, but still very common.
ID=04 Zero Divide Error
This error results if the microprocessor divides two numbers, and
the divisor is zero. Sometimes a programmer puts these in as debugging
aids, and then forgets to take them out.
ID=05 Range Check Error
Programmers can use an instruction in the Motorola 68000 to check
if a number is within a certain range. This error indicates that
the number tested isn't in the specified range.
ID=06 Overflow Error
Each number stored in a computer is given a certain amount of space.
The larger the number, the more space is needed to represent the
number. An overflow condition results if a generated number is too
big for its allotted space. A Motorola 68000 instruction tests for
an overflow condition, and displays this error if it detects an
ID=07 Privilege Violation
The Motorola 68000 runs in Supervisor or User mode. The Macintosh
should always be in Supervisor mode, but sometimes is placed in
User mode. Some of the instructions can only be executed in Supervisor
mode. If the computer attempts one of these instructions while in
User mode, a Privilege Violation error results.
ID=08 Trace Mode Error
A programmer can use a runtime debugger while in Trace mode. This
allows tracing through a program one instruction at a time. You
see this error if a debugger isn't installed and the 68000 is accidentally
placed in Trace mode.
ID=09 and ID=10 Line 1010 & 1111 Trap
There are many routines in the Macintosh ROM that can be called
by placing instructions in a program that aren't in the 68000's
vocabulary. When the 68000 encounters such an instruction, it looks
it up in the instruction table. This table gives the location of
routines paired with each instruction. If it finds an entry in the
table for the instruction, it branches to the routine. If there's
no entry for the instruction, you see one of these errors.
ID=12 Unimplemented Core Routine
A programmer might set breakpoints in parts of a program to inspect
for errors. This requires using a debugger. If a debugger isn't
installed when a breakpoint occurs, you see this error code.
ID=13 Uninstalled Interrupt
The Macintosh uses an interrupt to identify when devices like keyboards
and disk drives need service. Routines must be available in memory
to tell the computer how to service the device. If those routines
aren't available, you see this error.
ID=15 Segment Loader Error
Macintosh programs are broken up into segments, and each program
will always have at least one segment. Multiple segments allow loading
parts of the program into memory to provide more room for data in
internal RAM. The segment loader is responsible for loading a needed
segment into RAM. If the segment loader can't do this, you'll see
ID=17 through ID=24 Missing Packages 0-7
The Macintosh uses packages to do specific tasks. Some of the packages
are International Utilities, Binary-Decimal Conversion, Standard
File Utilities, and Disk Initialization. These packages are located
in the System file. If you get these errors, you probably have a
damaged System file. Error codes 15, 16, 26, 27, 30, and 31 also
come up when the System file is damaged. Try replacing the System
ID=25 Memory Full Error
You've probably run out of RAM. But you can get this error when
an earlier error causes the Macintosh to falsely detect an out-of-memory
ID=26 Bad Program Launch
The Macintosh couldn't execute the application opened.
ID=28 Stack Ran into Heap
This is similar to the Memory Full error. It's a good idea to save
your work frequently, and keep current backups of your hard disk
data. When a system crash does occur, you'll lose less data if you've
taken these precautions.
Troubleshooting System Errors
It's a good idea to save your work frequently, and keep current
backup copies of your hard disk data. When a system crash occurs,
you'll lose less data if you've taken these precautions.
If you're getting system errors frequently, investigate these possibilities:
- Try to open the document
with a current version copy of the application.
- Try opening other documents
with the same copy of the application.
- Check to see if the document
size exceeds the application size limits.
- Boot your system with
extensions off (restart while holding the Shift key down).
- Any changes (new Control
Panels, extensions, etc.) you've made to the system might give
you a clue to the cause of the crashes.
- Make a note of the desk
accessories you had open at the time of the crash and exactly
what you did before the crash.
- Make a note of the error
ID or text, and the version numbers of the application and system
software you were using.
- Try to recreate the problem
on another Macintosh.
- Cleanly install your
system software and try the application again.