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

Chapter 5 ■ Programs with Repetition Logic
Note, particularly, that we get a number before we enter the while loop. This is to ensure that
the while condition makes sense the first time. (It would not make sense if num had no value.)
To find the sum, we need to:
• Choose a variable to hold the sum; we will use sum.
• Initialize sum to 0 (before the while loop).
• Add a number to sum (inside the while loop). One number is added each
time through the loop.
On exit from the loop, sum contains the sum of all the numbers entered.
The while construct lets us execute one or more statements repeatedly as long as some
condition is true. Here, the two statements
add num to sum
get another number, num
are executed repeatedly as long as the condition num is not 0 is true.
In pseudocode, the while construct is usually written as follows:
while <condition> do
statements to be executed repeatedly
endwhile
The statements to be executed repeatedly are called the body of the while construct
(or, simply, the body of the loop). The construct is executed as follows:
1. <condition> is tested.
2. If true, the body is executed and we go back to step 1; if false, we
continue with the statement, if any, after endwhile.
We now show how the algorithm is executed using the sample data entered above. For easy
reference, the data was entered in the following order:
24 13 55 32 19 0
Initially, num is undefined and sum is 0. We show this as follows:
num
sum 0
24 is entered and stored in num;
num is not 0 so we enter the while loop;
num (24) is added to sum (0), giving:
num 24 sum 24
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