Цикл For и While

#include "stdafx.h"
#include <iostream>
#include <math.h>
#include <iomanip>
#include <fstream>
using namespace std;
double func_U(double arg_x, double arg_y)
{
double U1;
if(abs(pow(arg_x,2.0)+pow(arg_y,2.0))<=5) U1=tan(pow(arg_x,5.0)+arg_y);
else if(abs(pow(arg_x,2.0)+pow(arg_y,2.0))<13) U1=pow(arg_x,2.0)+pow(arg_y,3.0);
else U1=abs(arg_x-arg_y);
return U1;
}
int main()
{
fstream f;
f.open("Tot_samuu_file1.txt",ios::out);
double x_n, y_n, x_k, y_k;
double hx, hy;
double x, y,xmin,ymin,xmax,ymax;
double U,umax,umin;
double S,SredneeArifmeti4eskoe;
int K;
x_n = -11.0; x_k = 7.4;
y_n = 0.0; y_k = 1.0;
hx = 4.6; hy = 0.2;
umax=-1E10; umin=1E10;
S=0; K=0;
cout.setf(ios::right);
cout.setf(ios::fixed);
cout.precision(3);
cout<<setw(10)<<"x"<<setw(10)<<"y"<<setw(10)<<"U(x, y)"<<endl;
f<<setw(10)<<"x"<<setw(10)<<"y"<<setw(10)<<"U(x, y)"<<endl;
for ( x=x_n; x<=x_k; x+=hx ) {
y = y_n;
for ( y=y_n; y<=y_k; y+=hy ) {
U = func_U(x, y);
cout<<setw(10)<<x<<setw(10)<<y<<setw(10)<<U<<endl;
f<<setw(10)<<x<<setw(10)<<y<<setw(10)<<U<<endl;
if(U<umin){umin=U;xmin=x;ymin=y;}
if(U>umax){umax=U;xmax=x;ymax=y;}
S=S+U;K++;
}
}
printf("\n umax=%5.3f xmax=%5.3f ymax=%5.3f\n",umax,xmax,ymax);
printf("\n umin=%5.3f xmin=%5.3f ymin=%5.3f\n",umin,xmin,ymin);
if(K!=0){SredneeArifmeti4eskoe=S/K;printf("\n SredneeArifmeti4eskoe=%5.2f \n",SredneeArifmeti4eskoe);}
else printf("\n SredneeArifmeti4eskoe ne cywestvyet \n");
f<<"umin="<<umin<<endl;
f<<"umax="<<umax<<endl;
f<<"xmin="<<xmin<<endl;
f<<"xmax="<<xmax<<endl;
f<<"ymin="<<ymin<<endl;
f<<"ymax="<<ymax<<endl;
f<<"SredneeArifmeti4eskoe="<<SredneeArifmeti4eskoe<<endl;
char st;
cin>>st;
f.close();
return 0;
}