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In Chapter 12, you learned about the while
statement:
while (Boolean expression) embedded statement
The
while reading pattern consists of a
while statement with a read expression in the place
reserved for a Boolean expression:
while (read expression) embedded statement
The value of a read expression, such as
scanf ("%lf%i", &price, &number), normally is the number of
successfully assigned arguments.
Thus, the following while statement will continue looping, as
you type numbers, because the value of the call to scanf
is 2, rather than 0:
while (2 == scanf ("%lf%i", &price, &number)) {
...
}
When you decide to stop the loop, assuming that you are working with a
typical version of the Unix or Dos operating systems, you can arrange
for the scanf call to stop reading before all variables are
assigned, thus stopping the while loop, by typing the appropriate
keychord.
You are said to type a keychord whenever you hold down one key while
you press another. For example, if you are working with a typical version
of Unix, you tell the scanf function to stop reading by holding
down the control key and pressing the d key, thereby typing
the control-d keychord.