4-6
Error
Messages
and
Debugging
An error in a program
is
called a
"bug"
, and tracing and correcting this error
is
called "debugging".
Debugging can
be
carried
out
easily in the computer since
it
is
provided with an
automatic check mechanism that displays an error message
if
there
is
an error in
program execution or in the grammar
of
the BASIC language.
It
is
important
to
trace bugs persistently since there may be certain cases when a bug does
not
become an actual error
but
the desired results cannot be obtained.
1. Debugging with the Error Message
With the display
as
shown below, the error message reveals
the
type
of
the error,
the program area and the line number where the error occurred.
Type
of
error
__j'
L L Line number where
the
error occurred
Program area where
the
error occurred
The Error 2 display
is
called an
"error
code"
and indicates the type
of
error. The
various error codes are shown in the following list together with causes and
countermeasures (debugging methods).
67
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