void per()
{
    FILE *fz,*ft,*fs,*fd;
    int flag,v,c=1,i=1;
    long int kol;
    char buf[256], cp[13];
    clrscr();
    if ( (ft=fopen("skidki.dat","r+b"))==0 ) 
    {
        cout<<endl<<"недостатньо інформаціі";
        getch();
    }
    else
        if( (fs=fopen("tov.dat","r+b"))==NULL ) 
        {
            cout<<endl<<"недостатньо інформаціі";
            getch();
        }
        else
            if( (fz=fopen("zakazi.dat","r+b"))==NULL ) 
            {
                cout<<endl<<"недостатньо інформаціі";
                getch();
            }
            else
                if ( (fd=fopen("dost.dat","r+b"))==NULL )
                {
                    cout<<endl<<"недостатньо інформаціі";
                    getch();
                }
                else
                {
                    fclose(ft);
                    fclose(fs);
                    fclose(fd);
                    fclose(fz);
                    fz=fopen("zakazi.dat","r+b");
                    ft=fopen("znuwku.dat","rb");
                    fs=fopen("tov.dat","rb");
                    fd=fopen("dost.dat","rb");
                    kol=sizeof(mag);
                    fread(&mag,sizeof(mag),1,fz);
                    fread(&tov,sizeof(tov),1,fs);
                    
                    while(!feof(fz))
                    {
                        rewind(fs);
                        fread(&tov,sizeof(tov),1,fs);
                        while(!feof(fs))
                        {
                            if (strcmp(tov.nazv,mag.naz)==0) 
                            {
                                mag.st=tov.zena;
                            }
                            fread(&tov,sizeof(tov),1,fs);
         
                        }
                        fd=fopen("dost.dat","rb");
                        fread(&dos,sizeof(dos),1,fd);
                        if (strcmp(mag.dost,"курьєр")==0)
                        {
                            mag.st=mag.st+dos.st_k;
                        }
                        else
                            if (strcmp(mag.dost,"пошта")==0)
                            {
                                mag.st=mag.st+dos.st_p;
                            }
                            else
                            {
                                mag.st=mag.st+dos.st_s;
                            }
                        
                        rewind(ft);
                        fread(&ski,sizeof(ski),1,ft);
                        while(!feof(ft))
                        {
                            if ( (mag.d>=ski.d_n)&&(mag.d<=ski.d_k) ) flag=1;
                            if ( (mag.m>=ski.m_n)&&(mag.m<ski.m_k) ) flag=1;
                            if ( (mag.g>=ski.g_n)&&(mag.g<=ski.g_k) ) flag=1;
                            
                            if (flag)
                            {
                                mag.skid=ski.proc;
                            }
              
                            fread(&ski,sizeof(ski),1,ft);
                        }
                        
                        if (strcmp(mag.tal,"є")==0) flag=1;
                        else 
                        {
                            flag=0;
                            mag.st=mag.st-(mag.st/100)*mag.skid;
                        }
                        
                        if (flag)
                        {
                            if (flag) mag.st=mag.st-(mag.st/100)*5;
                        }
                 
                        fseek(fz,-kol,1);
                        fwrite(&mag,sizeof(mag),1,fz);
                        fread(&mag,sizeof(mag),1,fz);
                    }
         
                }
        
    fclose(fz);
    fclose(fd);
    fclose(ft);
    fclose(fs);
}

void pererahuvannya()
{
FILE  *ftov;

int kol,c=1;

clrscr();

ftov=fopen("tov.dat","r+b");

fread(&tov,sizeof(tov),1,ftov);

rewind(ftov);

while(!feof(ftov))

    {
         tov.zena+=100;

         fseek(ftov,(c-1)*sizeof(tov),1);

         fwrite(&tov,sizeof(tov),1,ftov);
         c++;
         fread(&tov,sizeof(tov),1,ftov);


   }
   fclose(ftov);
}

//створюю файл
void create_base()
{
     int a = 0;
    
    struct tovari
    {
        char nazv[15];
          float zena; //float
    }tov;  
    
    FILE  *ftov;
    int kol,c=1;
    //clrscr();
        ftov = fopen("C:\\tov.dat","w+");
 
    //fseek(ftov,(c-1)*sizeof(tov),1);   
    rewind(ftov); 
   
    tov.zena = 10;
        tov.nazv[0] = 's';
    tov.nazv[1] = 'a'; 
    fwrite(&tov,sizeof(tov),1,ftov);

    tov.zena = 20;
        tov.nazv[0] = 'l';
    tov.nazv[1] = 'g'; 
    fwrite(&tov,sizeof(tov),1,ftov);

    tov.zena = 30;
        tov.nazv[0] = 'v';
    tov.nazv[1] = 'i'; 
    fwrite(&tov,sizeof(tov),1,ftov);

    fclose(ftov);
}

//перезаписую по одній
void pererahuvannya()
{
     struct tovari
    {
        char nazv[15];
          float zena;
    }tov;  
    
    FILE  *ftov;
    int kol,c=1;
    //clrscr();
    ftov=fopen("C:\\tov.dat","r+");
 
    rewind(ftov); 
    while( 1 )
    {
        if ( fread(&tov,sizeof(tov),1,ftov) <= 0 ) break;  
        tov.zena += 100;

        int offset = ftell(ftov) - sizeof(tov);
        fseek(ftov, offset, 0);
        fwrite(&tov, sizeof(tov), 1, ftov);
        
        offset = ftell(ftov) + sizeof(tov)*0;
        fseek(ftov, offset, 0);
    }
    

    rewind(ftov);
    while( 1 )
    {
        if ( fread(&tov, sizeof(tov), 1, ftov) <= 0 )
            break;
        else
            printf("%s - %f;\n", tov.nazv, tov.zena);

    }
    fclose(ftov);
}

void main(char* args[])
{
    create_base();
    pererahuvannya();
}

void per()
{
FILE  *ftov;

int kol;

clrscr();
 ftov=fopen("tov.dat","r+b");
     kol=sizeof(tov);
     fread(&tov,kol,1,ftov);
     while(!feof(ftov))
     {
     tov.zena=tov.zena+100;
     fseek(ftov,-kol,1);
     fwrite(&tov,sizeof(tov),1,ftov);
     fseek(ftov,kol,kol);
     fread(&tov,sizeof(tov),1,ftov);
    }
   fclose(fs);
}