BASIC-SO
Commands
and
Statements
ERROR expression
10
INPUT
A,B,C
12
IF
B=O
THEN ERROR
11
14
PRINT
AlB
20
END
RUN
? 40,0,17
DIVISION BY ZERO
IN
12
Ok
EXIT The EXIT command terminates operation
of
the BASIC-80 interpreter and returns
control to ISIS-II.
EXIT
closes all open files, but does not automatically save pro-
grams.
If
you EXIT without saving the current program, it will be lost.
EXIT
FIELD The FIELD statement
is
used to allocate space within one
of
six
128-byte BASIC-80
random file buffers. When a random 110 transaction occurs, data move to or from
the specified random file buffer to
or
from disk sectors. The FIELD statement
associates the data with its position in the
110
buffer
so
that future references to the
specified variable will access the proper string characters or numbers within the
record stored in the random file buffer. The example below shows how FIELD
is
used. For further information, refer to the BASIC-80 Disk
Input/Output
section.
FIELD # file number,
number of characters AS string variable
[,number of characters AS string variable] ...
The program below opens random file
:F1
:FILE.1 and asks for five 30-character
strings to insert into
:Fl
:FILE.1.
10
OPEN
"R"
,#1,
":F1
:FILE.1"
20
FIELD #1,30 AS A$
30
FOR 1=1 to 5
40
INPUT
Z$
50
LSET
A$
=
Z$
60
PUT#1,1
70
NEXT I
80
CLOSE#1
90
END
FOR-NEXT-STEP The FOR-NEXT statement allows the execution
of
a given group
of
lines a given
number
of
times. As shown in the example below,
on
each iteration
of
the routine,
value A
is
incremented by the value given in the STEP instruction.
If
no value for
STEP
is
specified, the increment
is
1.
The instruction lines following the line con-
taining the
FOR
instruction are executed until the NEXT instruction
is
encountered.
Program control returns to the FOR instruction line, STEP
is
added to the value of
A, and the routine
is
reentered. When variable A exceeds the TO expression, control
passes to the instruction line following the NEXT instruction line.
6-7