Radio Shack TRS-80 Model 100 Basic Manual page 149

Line 128 The names of the five days of the week are displayed in column heading
form.
Lines 138 - 148 The values of the five medians stored in the array M are printed.
M(l) contains the median for Monday,
M(2)
the median for Tuesday,etc.
Line 158 The END statement terminates execution of the program. Without the END
statement, execution would continue with lines 500 - 570. If that were to happen, the
RETURN statement in line 570 would generate an error message because there was no
corresponding GOSUB statement. The STOP statement could have been used instead
of the END statement.
Lines 588 • 578 This is the subroutine which sorts the array S and compute,s the
median. Before this subroutine can be used (or "called"), the variable S must have
the appropriate values assigned to it. Upon returning from the subroutine, the median
is stored in the variable MD.
The subroutine can be called as many times as necessary in a program as long as the
input variables (N and S) are initialized before it is called. When the RETURN
statement is executed, control jumps to the statement immediately following the
GOSUB statement.
Here are some rules governing the use of subroutines.
1) Every subroutine must contain a RETURN statement. It may contain more
than one RETURN statement,
if
there are several places in the subroutine
from which you want to return.
2) A program may contain several subroutines.
3) A subroutine may call another subroutine.
4) A subroutine may be placed anywhere in a program, as long as it is executed
only from a GOSUB call.
Subroutines are very useful in programming. They allow you to avoid repetitive blocks
of code. They also allow you to write your program in modules or blocks so that it is
easier to write and to understand. The program in this experiment was simplified by
putting the sorting and median calculation in a subroutine.
What you have learned:
In this lesson you have seen how arrays, both one and two dimensional, can be used
to store data, so that certain information can be extracted. The TAB statement was
used with the PRINT statement to space the output. Two types of averages were
calculated, the mean and the median. To calculate the median it was necessary to sort
the data. The INT function was useful in simplifying the calculation of the median.
Finally, subroutines can often be used to make your program easier to write and more
readily understandable.
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