C program not running but getting compiled with no errors

Question

this is the program in question:

#include <stdio.h>
#include <tgmath.h>
#include <simpio.h>

long main(){
    long cars_t,years;
    cars_t=80000;
    years=0;
    while (cars_t<=160000){
        cars_t=ceil(cars_t*(1+7/100));
        years+=1;
    }
    printf("Xronia:%ld\n",years);
    printf("Arithmos Autokinhton:%ld\n",cars_t);
}

Just an extremely simple program with a while function. But for some reason it doesn't give any output at all. What i have noticed however is that, the moment i remove the while function(and the code inside of it) the program runs perfectly fine. Can anyone tell me how to fix this? thanks in advance.

cars_t*(1+7/100) this is a pretty slow rate of growth to start with, but regardless, 7/100 equals 0 due to integer division, 1 + 0 = 1, and thus you are simply assigning the value of cars_t to itself and it likely isn't even increasing. To avoid this, at least do cars_t=ceil(cars_t*(1+7.0/100)) — h0r53
– h0r53, Commented Nov 1, 2021 at 14:58
Yup it worked. Thanks. Believe it or not, this is actually a university project, im on my first year of computer science and they are pretty much starting us off with the basics. — CheatHydra
– CheatHydra, Commented Nov 1, 2021 at 15:04
You should have put an appropriate printf into the loop and you would have found out yourself. BTW a program compile without error or warnings is by no means a guarantee that it runs as expected. — Jabberwocky
– Jabberwocky, Commented Nov 1, 2021 at 15:14
^^^^^^ 'first year of computer science and they are pretty much starting us off with the basics' - demand to be taught basic debugging before you write one more line of code. If you cannot debug, you cannot program computers:) — Martin James
– Martin James, Commented Nov 1, 2021 at 16:41

SamBob · Accepted Answer · 2021-11-01 14:59:56Z

4

This is because you have declared cars_t as an integer (long) value, and 7/100 which are also also integers and so evaluate to zero. Hence you get stuck in the loop as cars_t does not increase.

Instead you want cars to be a floating value and force 7/100 to be evaluated as floating:

#include <stdio.h>
#include <tgmath.h>

long main(){
    long years;
    double cars_t;
    cars_t=80000;
    years=0;
    while (cars_t<=160000){
        cars_t=ceil(cars_t*(1+7.0/100));
        years+=1;
    }
    printf("Xronia:%ld\n",years);
    printf("Arithmos Autokinhton:%lf\n",cars_t);
}

https://onlinegdb.com/vNusyZ9xD

answered Nov 1, 2021 at 14:59

SamBob

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