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

Chapter 7 ■ Functions
This fetches the next positive integer from the input, regardless of how many and what kind of
characters come before it, and stores it in id. Recall that scanf("%d", &id) works only if the next
integer is preceded by zero or more whitespace characters. Our getInt is more general.
We test it by rewriting Program P4.2, which requests two lengths given in meters and
centimeters and finds the sum. We observed then that the data must be entered with digits only.
If, for instance, we had typed 3m 75cm we would have gotten an error since 3m is not a valid integer
constant. With getInt, we will be able to enter the data in the form 3m 75cm. The new program is
shown as Program P7.11.
Program P7.11
//find the sum of two lengths given in meters and centimeters
#include <stdio.h>
#include <ctype.h>
int main() {
int m1, cm1, m2, cm2, mSum, cmSum, getInt();
printf("Enter first length: ");
m1 = getInt();
cm1 = getInt();
printf("Enter second length: ");
m2 = getInt();
cm2 = getInt();
mSum = m1 + m2; //add the meters
cmSum = cm1 + cm2; //add the centimeters
if (cmSum >= 100) {
cmSum = cmSum - 100;
mSum = mSum + 1;
}
printf("\nSum is %dm %dcm\n", mSum, cmSum);
} //end main
int getInt() {
char ch = getchar();
// as long as the character is not a digit, keep reading
while (!isdigit(ch)) ch = getchar() ;
// at this point, ch contains the first digit of the number
int num = 0;
while (isdigit(ch)) { // as long as we get a digit
num = num * 10 + ch - '0'; // update num
ch = getchar();
}
return num;
} //end getInt
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