Trouble finding remainder in C

Question

program is supposed to convert a user inputed number of minutes into days, hours, and minutes

 #include <stdio.h>

 int main(void) {



 int input_minutes, minutes, r_minutes;  
 int days, hours;
 float r_days, r_hours;


 printf("Enter a number of minutes: ");
 scanf("%d", &input_minutes); 

 days = input_minutes / 1440;

Here is where I want to get the remainder of input_minutes divided by 1440 but instead I am getting 160.00007 when I compile.

 r_days =  input_minutes % 1440;
 hours = r_days * 24;
 r_hours = (r_days * 1440) - hours;
 minutes = r_hours * 60; 

 printf("r_days = %f", r_days);

 printf("This represents:%d days, %d hours, %d minutes\n",days, hours,        minutes);

@WeatherVane: Just updated myself on this, and the standard is on your side. Sorry for the confusion. — 3442, Feb 06 '17 at 21:44
@KemyLand today, the signature can be `int main(void)` or `int main(int argc)` or `int main(int argc, char *argv[])` or `int main(int argc, char *argv[], char *env[])`. — Weather Vane, Feb 06 '17 at 21:47
@WeatherVane, I don't know any platform that allows `int main(int argc)`. — Jens Gustedt, Feb 06 '17 at 22:41
@JensGustedt MSVC allows it: `int main(int argc) { printf("argc=%d\n", argc); }` reports the number of arguments. No compiler warnings. — Weather Vane, Feb 06 '17 at 22:44
@JensGustedt ...which could be useful for a program that does not accept more arguments than the executable name, and so does not need to know what they are, only there are too many. — Weather Vane, Feb 06 '17 at 22:50
@WeatherVane, oh, MSVC. It still does not seem to be conforming to any C standard, and doesn't seem to make much of an attempt for getting closer. So I often forget that it even exists. — Jens Gustedt, Feb 06 '17 at 22:53
@JensGustedt I somehow knew you would say that. However, it can't be a platform "you do not know of". I find it remarkable that non-standard gcc extensions are "good" but "MSVC" is always bad. By the way I drive a Skoda. They are wonderful. Let's strike a deal: if you drive a better car, please don't make it an ego trip. — Weather Vane, Feb 06 '17 at 22:53
@JensGustedt however from your profile, I congratulate you for turning away from C++. — Weather Vane, Feb 06 '17 at 23:01

score 4 · Answer 1 · edited May 23 '17 at 11:53

4

There are no valid reasons to use float types here (no division involved, except for the integer modulo). Using float only causes the loss of precision and problems to represent & display an integer properly as you have experienced.

quickfix:

int r_days, r_hours;

and

printf("r_days = %d", r_days);

see also: Is floating point math broken?

edited May 23 '17 at 11:53

Community

1
1

answered Feb 06 '17 at 21:20

Jean-François Fabre

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score 2 · Answer 2 · answered Feb 06 '17 at 21:25

You might want to change the logic of how you calculate the hours and minutes. Days calculation seems okay.

r_days =  input_minutes % 1440;
hours = r_days/60;
minutes = r_days % 60;
printf("This represents:%d days, %d hours, %d minutes\n",days, hours, minutes);

Trouble finding remainder in C

2 Answers2