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

Chapter 5 ■ Programs with Repetition Logic
Program P5.1
//print the sum of several numbers entered by a user
#include <stdio.h>
int main() {
int num, sum = 0;
printf("Enter a number (0 to end): ");
scanf("%d", &num);
while (num != 0) {
sum = sum + num;
printf("Enter a number (0 to end): ");
scanf("%d", &num);
}
printf("\nThe sum is %d\n", sum);
}
Of particular interest is the while statement. The pseudocode
while num is not 0 do
add num to sum
get another number, num
endwhile
is expressed in C as
while (num != 0) {
sum = sum + num;
printf("Enter a number (0 to end): ");
scanf("%d", &num);
}
When the program is run, what would happen if the very first number entered was 0? Since
num is 0, the while condition is immediately false so we drop out of the while loop and continue
with the printf statement. The program will print the correct answer:
The sum is 0
In general, if the while condition is false the first time it is tested, the body is not executed
at all.
Formally, the while construct in C is defined as follows:
while (<condition>) <statement>
The word while and the brackets are required. You must supply <condition> and
<statement>. <statement> must be a single statement or a block—one or more statements
enclosed by { and }. First, <condition> is tested; if true, <statement> is executed and
<condition> is tested again. This is repeated until <condition> becomes false; when this
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