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

Chapter 5 ■ Programs with Repetition Logic
To cater for this possibility, we can let the program validate the values of start and finish
to ensure that the “From” value is less than or equal to the “To” value. One way of doing this is to
write the following:
if (start > finish)
printf("Invalid data: From value is bigger than To value\n");
else {
printf("\n");
for (int m = start; m <= finish; m++)
printf("%2d x %d = %2d\n", m, factor, m * factor);
}
Validating data entered is yet another example of defensive programming. Also, it is better to
print a message informing the user of the error rather than have the program do nothing. This
makes the program more user friendly.
Another option here is not to treat a bigger start value as an error but simply print the table
in reverse order, going from largest to smallest. Yet another possibility is to swap the values of
start and finish and print the table in the normal way. These variations are left as exercises.
5.13 Temperature Conversion Table
Some countries use the Celsius scale for measuring temperature while others use the Fahrenheit
scale. Suppose we want to print a table of temperature conversions from Celsius to Fahrenheit.
The table runs from 0 degrees C to 100 degrees C in steps of 10, thus:
Celsius Fahrenheit
0 32
10 50
20 68
30 86
40 104
50 122
60 140
70 158
80 176
90 194
100 212
For a Celsius temperature, C, the Fahrenheit equivalent is 32 + 9C/5.
If we use c to hold the Celsius temperature, we can write a for statement to let c take on the
values 0, 10, 20, ..., up to 100, with
for (c = 0; c <= 100; c += 10)
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