Как правильно записать файл в текстовом формате? - C (СИ)

#include "stdafx.h"
 
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
 
static int   M;
 
// S - sigma
 
// insert def__I__nition
// warning C4100: 'A' : unreferenced formal parameter
// warning C4100: 'S' : unreferenced formal parameter
void step(double am2,double am1,double a0,double ap1,double S,double t,double tau,double h,double A,int M,double* u_old,double* u_new)
{
   int   k;
 
   for (k = 2; k <= M; k++)
   {
      u_new[k] = am2 * u_old[k - 2] + am1 * u_old[k - 1] + a0 * u_old[k] + ap1 * u_old[k + 1];
   }
 
   t += tau;
   
   // insert output condition
   for (k = 0; k < M; k++)
   {
      u_old[k] = u_new[k];
   }
 
   for (k = 0; k <= M; k++)
   {
      printf("\n x = %lf, u_old = %lf",k * h,u_old[k]);
   }
}
 
void initvalue(double* ff,int M,double h,double A,double t,double a)
{
   int      i;
   double   x;
 
   for (i = 0; i < M; i++)
   {
      x = i * h - a * t;
 
      if (x < 0.0)
      {
         x = A + x;
      }
 
      if ((x <= 0.0) && (x < A / 3.0))
      {
         ff[i] = 0.0;
      }
      else if ((A / 3.0 <= x) && (x <= (2.0 * A) / 3.0))
      {
         ff[i] = 1.0;
      }
      else if (((2.0 * A) / 3.0 < x) && (x <= A))
      {
         ff[i] = 0.0;
      }
   }
}
 
void myoutput(double h,int M,double* u_new)
{
   for (int j = 0; j <= M; j++)
   {
      printf("\n x = %lf, u_new = %lf",j * h,u_new[j]);
   }
}
 
// warning C4700: local variable 'A' used without having been initialized
// warning C4700: local variable 'h' used without having been initialized
// warning C4701: local variable 'max' may be used without having been initialized
// warning C4700: local variable 'A' used without having been initialized
// warning C4700: local variable 'h' used without having been initialized
// warning C4701: local variable 'max' may be used without having been initialized
void norma(int M,double t,double a,double* u_new)
{
   int      i;
   double   norm1;
   double   norm2;
   double   norm3;
   double   TVD;
   double*  u_exact;
   double   h;
   double   A;
   double   max;
 
   u_exact = (double*)malloc(M * sizeof(double));
 
   initvalue(u_exact,M,h,A,t,a);
 
   norm1 = 0.0;
   
   for (i = 0; i <= M; i++)
   {
      if (fabs(u_new[M]) >= max)
      {
         max = fabs(u_new[i]);
      }
   }
 
   norm1 = max;
 
   norm2 = 0.0; 
   TVD   = 0.0;
 
   for (i = 0; i <= M; i++)
   {
      norm2 += fabs(u_new[i] - u_exact[i]);
      TVD   += fabs(u_new[i] - u_new[i - 1]);
   }
 
   norm3 = 0.0;
   
   for (i = 0; i <= M; i++)
   {
      norm3 += (u_new[i] - u_exact[i]) * (u_new[i] - u_exact[i]);
   }
 
   norm3 = sqrt(norm3);
 
   printf("\n norm1 = %f",norm1);
   printf("\n norm2 = %f",norm2);
   printf("\n norm3 = %f",norm3);
   printf("\n TVD = %lf",TVD);
}
 
// warning C4189: 'T' : local variable is initialized but not referenced
// warning C4101: 'x' : unreferenced local variable
// warning C4101: 'k' : unreferenced local variable
// warning C4101: 'N' : unreferenced local variable
 
int main()
{
   double   A, S, a, h, tau, x;
   int      N, nt, k;
   double   am2, am1, a0, ap1;
   double   t  = 0.0;
   double   T  = 10.0;
   double*  u_new;
   double*  u_old;
 
   printf("\n Enter the value of A: ");
   scanf("%lf",&A);
   printf("\n Enter the value of M: ");
   scanf("%d",&M);
 
   u_old = (double*)malloc(M * sizeof(double));
   u_new = (double*)malloc(M * sizeof(double));
 
   printf("\n Enter the value of S: ");
   scanf("%lf",&S);
   printf("\n Enter the value of a: ");
   scanf("%lf",&a);
   printf("\n Enter the value of am2: ");
   scanf("%lf",&am2);
   printf("\n Enter the value of a0: ");
   scanf("%lf",&a0);
 
   // input of unsufficient coefficients
   h = A / M;
 
   printf("\n h = %lf",h);
   
   tau = S * h / a;
   
   printf("\n tau = %lf",tau);
   printf("\n S = %lf\n",S);
 
   am1 = 0.5 * ((1. + S) - 3.0 * am2 - a0);
   ap1 = 0.5 * ((1. - S) - a0 + am2);
 
   printf("\n am2 = %lf",am2);
   printf("\n am1 = %lf",am1);
   printf("\n a0 = %lf",a0);
   printf("\n ap1 = %lf\n",ap1);
 
   initvalue(u_old,M,h,A,t,a);
 
   for (nt = 1; nt < M; nt++)
   {
      step(am2,am1,a0,ap1,S,t,tau,h,A,M,u_old,u_new);
 
      if (nt / 10 == nt / 10.0)
      {
         myoutput(h,M,u_new);
      }
 
      norma(M,t,a,u_new);
   }
 
   return 0;
}