Note
The
syntax
of
BASIC imposes no limit
on
the
extent
to
which subroutines can be
nested
(that
is, on the
number
of
levels
of
subroutine calls which can be made from
other
subroutines); however, in practice a limitation
is
imposed
by
the
amount
of
free space in memory which
is
available for storing
return
addresses.
10
B=5
20
C=8
30
GOSUB
100
4-0
PRINT A
50
8=2
60
c =
10
70 GOSUB 100
30 PRINT A
90
END
ICJO
A=BtC
110
RETURN
(GOSUBIOO)
~
,-----------------7(
I
oo)
I
(A=B+c]
{i
(RETUR~
(
PRJNTA]13displayed.:
D
I
·)
(-
--
--
-
----
-----
--
~
[PRINTA
)12
displayed.
0
2. 3. 6. 4
IF~
THEN
.........
.
.........
. . . .
......
(abbreviated format:
...
IF~
TH.)
I Format I
IF
e THEN Ln
Function
IF
e THEN
statement
e: A relational expression
or
logical expression
Ln: Destination line
number
IF
...
THEN statements are used
to
control branching
of
program execution accord-
ing
to
the result
of
a logical
or
relational expression. When the result
of
such an
expression
is
true, statements following THEN are executed.
If
a line
number
is
specified following THEN, program execution
jumps
to
that
line
of
the program
if
the
result
of
the
expression is true.
If
the
result
of
the logical
or
relational expression
is
false, execution continues with
the program line following
that
containing the
IF
. . . THEN statement.
[!!] I Condition I THEN
11
Statement
or
line number
50------------------~----------------------------------------~----------
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