Teach Yourself Borland C++ in 14 Days - portal

NOTE
Wading In Deeper
The displayRecord() function, which begins on line 76, takes two parameters. The first
parameter, num, is an int that contains the index number of the record to display. This variable
is used only to display the record number. On line 78 I add 1 to num when I display it because
users are accustomed to lists beginning with 1 rather than with 0. (I aim to please!) The second
parameter of the displayRecord() function is an instance of the mailingListRecord structure.
Inside the displayRecord() function I use the local instance of the structure passed in
(which represents a copy of the structure) to display the contents of the structure.
In this case I am passing the mailingListRecord structure by value.
What this means is that a copy of the structure is created each time the
displayRecord() function is called. This is not very efficient because of
the overhead required to pass a structure by value. The overhead comes
in the form of the extra time and memory required to make a copy of
the structure each time the function is called. It would be better to
pass the structure by reference, but I haven’t talked about that yet,
because the structure is passed by value in this program. You will
learn about passing by reference tomorrow when we discuss functions
in C++.
Note that the displayRecord() function is called from both the for loop when all the records
are displayed (line 49) and again from the main body of the program to display the actual
record chosen (line 72). That’s precisely why the code to display a record has been placed in
a function. By putting it in a function, I only have to write the code once and can avoid
duplicating the code unnecessarily.
TIP
Any time you find yourself repeating code more than a couple times in
your programs, think about moving that code to a function. Then you
can call the function when you need that code executed.
There is another segment of this program that deserves mention. Look at this do-while loop,
which begins on line 59:
do {
rec = getch();
rec -= 49;
} while (rec < 0 || rec > 2);
This code first gets a character from the keyboard using the getch() function. As you have
63
2