Smple
Proce6Jres
100
PAPER
7:
CLS
•
110
INK 4
120
square
20,SO,SO
The numbers 20,50,50
are
called parameters and
they
are
passed
to
the variables named
In
the procedure definition
thus:
square 20,50,50
I
J.,/.
DEFine PROCedure square(side,ac,up)
The numbers
20,50,50
are
called actual parameters,
They
are
numbers
in
this case but
they could
be
variables or expressions,
The
variables
slde,ae,up
are called formal
parameters.
They
must
be
variables because the
'receIVE'
values.
A more interesting main program uses the same procedure
to
create a random pattern
of
coloured pairs
of
squares.
Each
pair
of
squares
is
obtained
by
offsetting the second
one across and up
by
one-fifth
of
the side length
thus:
•
36
Assuming that the procedure square
is
still
present
at
line
200 then the following program
will
have the
claSSical
effect
100
REMark
Squares
Pattern
110
PAPER
7 :
CLS
120
FOR
pa i r = 1
TO
20
130
INK RND(S)
140
LET
side
= RND(10
TO
20)
1S0
LET
ac =
RND
(SOl
:
up
=
RND
(70l
160
square
side,ac,up
170
LET
ac=ac+side/S
:
up
=
up+side/S
180
square
side,ac,up
190
END
FOR
pai
r
The advantage
of
procedures
are:
1.
You
can use the same code more than once
in
the same program or
in
others.
2.
You
can break down a task into sub-tasks and write procedures for each sub-task.
This helps the analysis and design.
3.
Procedures can be tested separately.
ThiS
helps the testing and debugging.
4.
Meaningful procedure names and clearly defined beginnings and ends help
to
make a program readable.
When
you
get used
to
properly named procedures
With
good parameter facilities, you
should find that your problem-solving and programming powers
are
greatly enhanced.
12/84
•
•
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