Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 5 ■ Programs with Repetition Logic
On exit from the for loop, the value of h (6, in this case) is available and may be used by the
programmer, if required. Note, however, that if h was declared in the for statement, it would be
unavailable outside the loop.
If we need a loop to count backwards (from 5 down to 1, say), we can write
for (int h = 5; h >= 1; h--)
The loop body is executed with h taking on the values 5, 4, 3, 2, and 1.
We can also count upwards (or downwards) in steps other than 1. For example, the statement
for (int h = 10; h <= 20; h += 3)
will execute the body with h taking on the values 10, 13, 16 and 19. And the statement
for (int h = 100; h >= 50; h -= 10)
will execute the body with h taking on the values 100, 90, 80, 70, 60, and 50.
In general, we can use whatever expressions we need to get the effect that we want.
In Program P5.10, h takes on the values 1, 2, 3, 4, and 5 inside the loop. We have not used
h in the body but it is available, if needed. We show a simple use in Program P5.11 in which we
number the lines by printing the value of h.
Program P5.11
#include <stdio.h>
int main() {
for (int h = 1; h <= 5; h++)
printf("%d. I must not sleep in class\n", h);
}
When run, this program will print the following:
1. I must not sleep in class
2. I must not sleep in class
3. I must not sleep in class
4. I must not sleep in class
5. I must not sleep in class
The initial and final values in the for statement do not have to be constants; they can be
variables or expressions. For example, consider this:
for (h = 1; h <= n; h++) ...
How many times would the body of this loop be executed? We cannot say unless we know
the value of n when this statement is encountered. If n has the value 7, then the body would be
executed 7 times.
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