Radio Shack TRS-80 User Manual page 103

The
Old Coin Toss Gambit.
Remember
now, you could
toss
a
thousand heads
in
a
row
and
the
odds on
the next
toss
are exactly
50/50 that a
head
will
come up
again.
Every
toss
is
totally
independent of
what
happened before
it,
IT
IS TOO!!!!!
In
the long run however, the
number
of heads
and
tails
should be exactly the same. {Casinos
live
off people
who
go broke
waiting for their particu-
lar
scheme
to
pay
off
. . .
"in the long run").
Your Computer
will
give
you
a complete edu-
cation
in
"odds" and
various
games
of chance,
and
allow
you
to
prove or disprove
many
ideas involving probability. This
is
known
as
computer "modeling"
or "simulation."
We're going to write
this
coin
toss
simulation
program
in
Radio Shack Shorthand and
use
multiple statement
lines just for
the
practice.
Type
it
in
very
carefully to avoid errors:
10
H=0tT=0:P.
20
IN.
"HOW MANY TIMES SHALL WE FLIP THE
COIN";F:CLS
30
P.
"YOU STAND
BY
WHILE
I
DO THE
FLIPPING
------
40
F.N=1T0F:X=RND(2
)
jONXG.
60,70
50
P.
"IT BOMBED! WAS NEITHER
A
1
NOR
A 2
.
"
\
END
60 H=H+1
sG.
80
70 T=T+1
80 N,N
jP. :P
.
sP
.
iP.
90
P.
"HEADS TAILS TOTAL
FLIPS' P.
tP.H.T.F
100
P.
100*H/F;
"
%
"
,
100*T/F
s
:P. :P,
. . .
and
RUN.
"Flip the coin"
100
times
on
the
first
RUN
to
get a feel for
the
program and
the run
time.
RUN
as
many
times
as
it
takes to
convince
you
that the
random number
generator produces
really
random
numbers.
When
it's
time
for
lunch or
you
can wait quite
awhile
for
the answer,
try 25,000
flips
or
more.
Program
analysis:
Line 10
contains 3 statements.
The
first
initializes
H
(for Heads)
at zero.
The
second
sets
T
(for Tails)
equal
to zero.
The
third inserts
a space
in
the printout with a PRINT(P.).
Line 20 has 2 statements.
1
—
Inputs the
number
of
flips
desired.
2
—
A
clear
screen
(CLS)
to
start
the
next
print
line
at the top
of the
screen.
Line 30
Prints a
"Standby"
statement.
Line 40
has 3 statements.
1
—
Begins a
FOR-NEXT
loop that
runs
"F"
times.
2
—
Is
"VOU IOSH"
101