Thread: What is linker error in function programs?

I am getting this error-
Linker error:Undefined symbol(Calsum)in module(the address where the program has been saved)

Code:

main()
{
int a,b,c,sum;
printf("Enter any three numbers");
scanf("%d %d %d",&a &b &c);
sum=calcum(a,b,c);
printf("Sum=%d",sum);
}
calsum(int x,int y,int z)
{
int d;
d=x+y+z;
return(d);
}

lol thanks