The read-only system variable ERR contains a value corresponding to the last error encountered. When the system is started, ERR has the value 0. Other values (adapted from the help file) are:
1: Syntax Error. There is problematic grammar in the program.
2: Out of range. The value exceeds the valid range.
3: Out of memory. There is insufficient memory available.
4: Undefined label. The destination for a branch instruction cannot be located.
5: NEXT without FOR. There is a NEXT command which does not belong to any FOR command.
6: Out of DATA. There is insufficient DATA available for a READ command.
7: Illegal function call. There is a problem with the assignment of elements in a function or command.
8: Duplicate definition. The same array or variable has been defined more than once.
9: Can't continue. A program cannot be continued using a CONT command.
10: Missing operand. There are insufficient parameters.
11: Duplicate label. The same label has been defined more than once.
12: Illegal resource type. The resource type designated by a string does not exist.
13: Illegal character type. The designated character type does not exist.
14: String too long. The string is too long. Labels should be no longer than 8 characters, while strings should be no more than 256 characters in length.
15: Division by zero. A number has been divided by zero.
16: Overflow. The results of an operation have exceeded the permitted range.
17: Subscript out of range. The subscript for an array variable is out of range.
18: Type mismatch. Variable types do not match.
19: Formula too complex. The formula may have too many bracketed sections, or otherwise be too complex.
20: RETURN without GOSUB. A RETURN command is present without an accompanying GOSUB command.
21: FOR without NEXT. A FOR command is present which does not correspond to a NEXT command.
22: Illegal MML. There is an error in the MML.
This system variable is often used in conjunction with ERL.