Program crashed, no compilation errors

Code:

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#include <stdio.h>
#include <stdlib.h>

int primecheck(int N, int Y);
void main()
{
int u,l,x;
float z,a;
while(scanf("%d %d",&u,&l)==2){
if(l>u){
u=a;
l=u;
a=u;
}
x=primecheck(u,l);
z=(x/(l-u))*100;
printf("%f",x);
}
}

int primecheck(int N, int Y)
{
    int c=0,i,k;
    for(i=N; i<=Y; i++){
    k=(i*i)+i+41;
    if(k%2!=0){
    c++;
    }
    }
    return c;
}

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no compilation errors. but program crashed. newbie here T_T

Quote:

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Originally Posted by kaopei

no compilation errors. but program crashed. newbie here T_T

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Please note that in future "program crashed" is not in any way a good description of what's happening. You need to give as much information as you can. I only saw when I ran it that the program gives a floating point exception which, in most circumstances, is caused by dividing by zero. Since the only division in your program is this line:

Code:

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z=(x/(l-u))*100;

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It must be that l - u is 0, so l and u are equal. I see earlier in your code that this happens:

Code:

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if (l > u) {
    u=a;
    l=u;
    a=u;
}

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(oh and please use proper indentation in your code, it makes it so much easier to read)

What do you think this code does? It actually sets all the variables u, l and a to be the same as the (originally uninitialised, and hence garbage) value of a, which I'm sure is not what you want.