Diese Prozedur löst einen Fehler der gleichen Art wie eingebaute Prozeduren aus. Dies kann in Nutzer definierten Prozeduren genutzt werden. ERROR erfordert als Parameter den Prozedurnamen und die Nummer der Fehlermeldung:

Nummer	Meldung
0	Syntax error
1	Unbalanced parenthesis
2	No expression present
3
4	L-value expected
5	Symbol table full
6	Double defined label
7
8	Call stack underflow
9	Call stack overflow
10	Too many nested controls
11	Controls unbalanced
12	Type already exists
13	Last code reached
14	Expression delimiter expected
15	No open IF
16	Unknown type
17	Unknown function
18	No open FOR
19	Default argument missing
20	Undefined constant
21	Unclosed IF
22	Type mismatch
23	Unclosed FOR
24	Undefined variable
25
26
27	Not implemented
28	Global variable exist
29	2D-Array needed
30	Index out of range
31	Array variable used before DIM
32	String too long
33	Memory full
34	String stack underflow
35	String stack overflow
36	Negative argument
37	Label expected
38	Wrong parameter
39	Failed
40	Unknown procedure
41	Invalid code address
42	Include stack overflow
43	Include file not found
44	Append file not found
45	Error position found
46	Too many parameters
47	Too less parameters
48	Nested procedure
49	ENDP without PROC
50	PROC or FUNC not at begin
51	Wrong version
52	Procedure already exists
53	Interrupted
54	Undefined label
55	Expected constant expression
56	Pointer expected
57	Division by 0
58	Wrong mode
59	No valid icon
60	No more data
61	Not found
62	Wrong font
63	Missing ENDP
64	Arrays must be VAR parameter
65	Coordinates out of range
66	VAR parameters not allowed here
67	Not initialized
68	Can't save overlay
69	Can't load overlay
70	Same overlay
71	File too big