BASIC-80
Commands
and
Statements
NEXT
The NEXT statement
is
used with a previous FOR statement
to
end
an
iteration of a
FOR-NEXT loop; when BASIC-SO encounters a NEXT statement, control passes
back to the statement line containing the last FOR statement.
If
no index variable
is
specified, BASIC-SO increments the variable specified in the last FOR statement.
Each NEXT can end more than one loop if the index variables used in each loop are
given separated by commas.
The syntax
of
NEXT
is:
NEXT [Variable] [, Variable] ...
10
FOR
A=1
TO 5
20
PRINT A * A;
30
NEXT A
40
END
RUN
1 4 9 16
25
Ok
NULL
The NULL command specifies the number
of
null characters printed
at
the end of a
printed line, following the carriage return. This feature
is
used with hard copy ter-
minals that require a certain number
of
null characters that set carriage return
timing.
NULL
number
of
null
characters
to
be
transmitted
ON ERROR GOTO
The ON ERROR OOTO statement transfers program control to the specified line
number when error conditions occur
or
an ERROR instruction simulates an error
within a program. The
ERR
function
is
set to the applicable error code and the ERL
function
is
set to the applicable line number.
The instruction line ON ERROR OOTO 0 removes the effect
of
any previous ON
ERROR OOTO, so
that
errors cause messages to print and halt execution.
If
ON
ERROR OOTO 0
is
executed within
an
error-handling routine (after an error but
before a RESUME) the proper error message prints and execution halts
immediately.
If
an error occurs in
an
error routine, after an ON ERROR OOTO branch and
before a RESUME, the ON ERROR OOTO has no effect. This means that if an ON
ERROR OOTO
is
in effect, and two errors (or ERROR commands) occur without
an intervening RESUME, the second error prints an error message and halt
execution.
ON ERROR GOTO
line
number
10
ON ERROR GOTO
200
20
ERROR
11
200
PRINT
"ERROR"
ERR
"AT
LINE"
ERL
210
RESUME NEXT
6-13