ERROR Codes

This page lists all the error codes defined in QB64 that can occur in a program when running. Unless overridden with an ON ERROR handler, these result in a dialog box appearing. Due to legacy holdovers from previous BASIC dialects, not all of these errors may actually occur in a program (unless manually triggered with ERROR).

If you encounter an error while editing in the QB64 IDE or when compiling (especially a "C++ Compilation Failed" message), or believe your program is correct, please report the error at https://github.com/QB64-Phoenix-Edition/QB64pe/issues.

It's recommended to exclude (whitelist) the entire "qb64" respectively "qb64pe" folder from any real-time anti-virus scanning to prevent generic strange errors when editing or compiling.

Recoverable errors

These errors can be triggered in QB64, and may be caught by an ON ERROR handler. The default error handler gives the user option to continue program execution.

Code	Description	Possible Cause
2	Syntax error	READ attempted to read a number but could not parse the next DATA item.
3	RETURN without GOSUB	The RETURN statement was encounted without first executing a corresponding GOSUB.
4	Out of DATA	The READ statement has read past the end of a DATA block. Use RESTORE to change the current data item if necessary.
5	Illegal function call	A function was called with invalid parameters, in the wrong graphics mode or otherwise in an illegal fashion. Illegal Function gives some suggestions.
6	Overflow	A numeric operation has resulted in a value beyond a variable's allowed range. See variable type.
7	Out of memory	Generic out of memory condition.
9	Subscript out of range	An array's upper or lower dimensioned boundary has been exceeded.
10	Duplicate definition	An array created with DIM was redefined with DIM or REDIM.
13	Type mismatch	A PRINT USING format string did not match the type of the supplied variables.
20	RESUME without error	The RESUME statement was encountered outside of an ON ERROR error handler.
50	FIELD overflow	The FIELD statement tried to allocate more bytes than were specified for the record length of a random access file.
51	Internal error	Generic error
52	Bad file name or number	A file handle was used that does not correspond to a valid opened file.
53	File not found	File error, see below
54	Bad file mode	A file operation was not compatible with the mode used in the OPEN statement.
55	File already open	An OPEN statement attempted to use a file handle that is already in use. Consider using FREEFILE.
59	Bad record length	The record length used for a RANDOM file was insufficient to perform the operation.
62	Input past end of file	A file was read past its end. Ensure EOF is being correctly checked.
63	Bad record number	The record (for RANDOM) or offset (for BINARY) is outside the allowed range.
64	Bad file name	File error, see below
68	Device unavailable	A serial port (COM device) failed to behave as expected
70	Permission denied	File error, see below
75	Path/File access error	File error, see below
76	Path not found	File error, see below
258	Invalid handle	An handle used for an image, sound, font etc. was invalid. Be sure to check the return values of functions like _LOADFONT and _LOADIMAGE.

Error handling of file operations varies between operating systems and is highly dependent on the exact circumstances. The errors marked "file error" above should all be equally treated as a generic failure to read or write from disk.

Critical errors

These errors can be triggered in QB64 but will not be caught by an ON ERROR handler. They are always fatal, causing the program to exit.

Code	Description	Notes
11	Division by zero	Only relevant for integer division, and may not be caught on all operating systems.
256	Out of stack space	Too many nested GOSUB calls.
257	Out of memory	Generic out of memory condition.
259	Cannot find dynamic library file	A .dll, .so or .dylib file referred to by DECLARE LIBRARY was not found.
260, 261	Sub/Function does not exist in dynamic library	A function declared with DECLARE LIBRARY does not exist.
270	_GL command called outside of SUB _GL's scope
271	END/SYSTEM called within SUB _GL's scope
300	Memory region out of range	Triggrered by _MEM commands
301	Invalid size	Triggrered by _MEM commands
302	Source memory region out of range	Triggrered by _MEM commands
303	Destination memory region out of range	Triggrered by _MEM commands
304	Source and destination memory regions out of range	Triggrered by _MEM commands
305	Source memory has been freed	Triggrered by _MEM commands
306	Destination memory has been freed	Triggrered by _MEM commands
307	Memory already freed	Triggrered by _MEM commands
308	Memory has been freed	Triggrered by _MEM commands
309	Memory not initialized	Triggrered by _MEM commands
310	Source memory not initialized	Triggrered by _MEM commands
311	Destination memory not initialized	Triggrered by _MEM commands
312	Source and destination memory not initialized	Triggrered by _MEM commands
313	Source and destination memory have been freed	Triggrered by _MEM commands
314	_ASSERT failed	See _ASSERT.
315	_ASSERT failed (check console for description)	See _ASSERT.
502 to 518	Out of memory	Generic out of memory condition.

Legacy errors

These errors will never be generated by a genuine error condition, and can only be triggered by explicit use of the ERROR command. They can all be caught by ON ERROR.

Code	Description
1	NEXT without FOR
8	Label not defined
12	Illegal in direct mode
14	Out of string space
16	String formula too complex
17	Cannot continue
18	Function not defined
19	No RESUME
24	Device timeout
25	Device fault
26	FOR without NEXT
27	Out of paper
29	WHILE without WEND
30	WEND without WHILE
33	Duplicate label
35	Subprogram not defined
37	Argument-count mismatch
38	Array not defined
40	Variable required
56	FIELD statement active
57	Device I/O error
58	File already exists
61	Disk full
67	Too many files
69	Communication-buffer overflow
71	Disk not ready
72	Disk-media error
73	Feature unavailable
74	Rename across disks

Custom errors

Any code not listed above may be used as a custom error code with ERROR to signal other errors in your application. To avoid confusion, it is a good idea to start at error code 100 and go up from there.

Other Errors

• Syntax errors: QB64 will display most statement syntax and parameter errors in the Status area below the editing area in the IDE. It may also show missing brackets or other syntax punctuation required. Check the keyword's syntax when necessary.
• Memory errors: Loading many resources with a function like _LOADIMAGE and not freeing (e.g. _FREEIMAGE) can cause out of memory conditions, especially when executed in a loop.
• CPU consumption: Loops will tend to use 100% of a processor by default. Consider using _LIMIT to restrict CPU usage.

See also

• ERROR (simulates error), ERR (error code number), ERL (closest line number when line numbers are used)
• ON ERROR (calls error handing routine using GOTO only), _ERRORLINE (actual text code line)
• _INCLERRORLINE, _INCLERRORFILE$, _ERRORMESSAGE$

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