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Floating point error in turbo c++

Mon, 02 Feb 2009 09:29:06 -0700

I wrote this code for a school project,since i use vista and dos doesn't work properly on it ,i normally use the emulator DOSBOX.The problem is this program runs well on DOSBOX but not on the normal DOS platform. It gives an error

 Floating point error:domain Abnormal program termination

Here's the code,its on text file encryption.My school requires me to use the ancient "turbo c++ 3.0"

#include<string.h>
#include<stdio.h>
#include<fstream.h>
#include<conio.h>
#include<math.h>

 int strtoken(char k[]) {
    int N = strlen(k);
    int sum = 0   ;

            for (int q=0;q<N;q++)
                sum+= (int) k[q] ;

    int tok = sum%255;

  return tok;
 }

int strtoken2(char k1[]) {

   int N1 = strlen(k1);
   int sum1 = 0,t=0;
        for (int q1=0;q1<N1;q1++)
        {
            t = (int) k1[q1];
            t=pow(2,t);
            sum1+= (t%255) ;
            }

  int tok = sum1%255;

  return tok;
}


 int main() {
     clrscr();
     int choice,num;
     char ifname[20],ofname[20],Key[20],ch;

start:
			  clrscr();
    cout<<"\n------------------------------------------------------------------------------\n";
	cout<<"Texcrypt 1.0.\n";
	cout<<"\n";
	cout<<"------------------------------------------------------------------------------\n\n";
	cout<<"\t\t\t*-------------------*\n"<<"\t\t\t| 1) Encrypt. |\n"<<"\t\t\t| 2) Decrypt. |\n"<<"\t\t\t| 3) Help.    |\n\t\t\t| 4) Exit.    |\n"<<"\t\t\t*-------------------*\n";
	cout<<"\nEnter your choice: ";

	cin>>choice;




if(choice==3) {
 clrscr();

cout<<" Instructions \n ------------- \n\n\n 1.Choose whether to encrypt or decrypt a file ";
cout<<"\n 2.Enter the input and output filenames (if the file is in same directory as texcrypt ,if not,then enter the full path of the file)";
cout<<"\n 3.Enter the key to encrypt/decrypt the file with(your file will be encrypted on the basis of the key entered).";
cout<<"\n 4.The output file will be your encrypted/decrypted file";
cout<<"\n\n\n\nPress any key to return ...... ";

getch();

goto start;






}






else if(choice==4)
	  return 0;
	      char text[3][20] = {"","encrypted","decrypted"};

	clrscr();
		cout<<"Enter input filename : ";
		gets(ifname);
		fflush(stdin);
		cout<<"\n";
		int i;

		ifstream infile("");
		ofstream outfile("");
		   infile.open(ifname);

		if(!infile) {          // if file is not found
		cout<<"Error:File not found";
		goto end;
		}

		cout<<"Enter output filename : ";gets(ofname);fflush(stdin);
		cout<<"\n";







		   outfile.open(ofname);


		       switch(choice) {

                        case 1:cout<<"Enter key: ";

                                for(i=0;;i++)
                                {


                                        Key[i]=getch();


				    if (Key[i] == '\r')
					break;
		       cout<<"*";
                                    }
                                Key[i] = '\0';

// I think the error is somewhere overhere
			    int token= strtoken(Key);
			    int token2= strtoken2(Key);

			  fflush(stdin);
			      cout<<"\n";

				     while (infile) {

				      while(infile){

					infile.get(ch);
					if(!infile){
					  cout<<"\nThe file was successfully encrypted.";
					  getch();
					  goto end;
					  }

					ch=char((ch+token-(token2))%255);

					outfile.put(ch);
					   }
					   }

			    break;


						  case 2:
				cout<<"Enter key: ";

				for(i=0;;i++){
				    Key[i]=getch();


				    if (Key[i] == '\r')
					break;
					cout<<"*";

						}
				Key[i] = '\0';
				cout<<"\n";
				     fflush(stdin);
                                     int dtoken=strtoken(Key);
                                     int dtoken2=strtoken2(Key);

                                     while(infile) {

                                     while(infile) {

                                          infile.get(ch);
                                          if(!infile)
                                          {
                                                cout<<"\nThe file was successfully decrypted.";
                                                getch();
                                                goto end;
                                                }
                                                ch=char(((ch)-dtoken+(dtoken2))%255);
                                                outfile.put(ch);

                                           }
                                           }
                                    break;
								 }
								//end switch
								end:
								 infile.close();
								 outfile.close();

								 cout<<"\n\n\nPress any key to return ......... "          ;

								 getch();
								 goto start;

								   return 0;
								   }

Re: Floating point error in turbo c++

Tue, 03 Feb 2009 01:22:05 -0700

I don't know what is causing the error, but I can give you some feedback on the code.

: Here's the code,its on text file encryption.My school requires me
: to use the ancient "turbo c++ 3.0"

That is a poor school then. You should download a free, modern compiler and use it on the side, so that you get chance to learn real standard C++.

:

: #include<string.h>
: #include<stdio.h>
: #include<fstream.h>
: #include<conio.h>
: #include<math.h>

 These header declarations aren't valid in C++. This is non-standard code that only works in TC.


 
:             t=pow(2,t);

I suspect this is what makes the error appear, since you aren't using float numbers elsewhere in the code. As a work-around, you could code an integer version of that function, it is quite simple to do.

Here is one you can use:

(change uint32 to unsigned long and uint16 to unsigned int)

uint32 gpfunc_intpow (uint16 base, uint16 exp)
{
  uint32 sum;

  if(exp == 0)                                   /* special case: x times 0 */
  {
    sum = 1;
  }
  else
  {
    uint16 i;

    sum = base;

    for(i=1; i<exp; i++)
    {
      sum *= base;
    }
  }

  return sum;
}



: goto start;

You should avoid using goto, it is frowned upon by a majority of the programming world, and can be replaced with loops, that are easier to read.




: 		fflush(stdin);

This is not standard C nor standard C++ and will not work on standard compilers. You can only fflush stdout, never stdin.

Re: Floating point error in turbo c++

Mon, 09 Feb 2009 09:05:22 -0700

thanks,i made some tweaks to get that exponent loop working and thanks for your suggestions on fflush too

Re: Floating point error in turbo c++

Wed, 11 Mar 2009 21:04:05 -0700

I'm getting the same problem too. Say, what sort of "modern compiler" would you recommend if I'm to give up using Turbo C++?

Re: Floating point error in turbo c++

Wed, 11 Mar 2009 23:22:33 -0700

Dev - C++
or
Visual C 07 (or higher)

Re: Floating point error in turbo c++

Thu, 12 Mar 2009 03:44:03 -0700

: I'm getting the same problem too. Say, what sort of "modern
: compiler" would you recommend if I'm to give up using Turbo C++?

Free compilers:
Dev C++ (gcc) www.bloodshed.net/dev/devcpp
Microsoft Visual Studio Express
Borland Turbo C++ Builder 2006 www.turboexplorer.com

Commerical compilers:
Embarcadero Builder 2009 (former Borland)
Microsoft Visual Studio 2008

Re: Floating point error in turbo c++

Sun, 16 Aug 2009 01:28:26 -0700

#include<math.h>
#include<stdio.h>
#include<conio.h>
#define EPS 0.000001
void main()
{
float F(float x);
float x1,x2,x3,x4,f1,f2,f3,f4,h1,h2,d1,d2,a0,a1,a2,h;
clrscr();
printf("\nInput three initial points \n");
scanf("%f %f %f",&x1,&x2,&x3);
f1=F(x1);
f2=F(x2);
f3=F(x3);
begin:
h1=x1-x3;
h2=x2-x3;
d1=f1-f2;
d2=f2-f3;
a0=f3;
a1=(d2*h1*h1-d1*h2*h2)/(h1*h2*(h1-h2));
a2=(d1*h2-d2*h1)/(h*h2*(h1-h2));
if(a1>0.0)
h=(-2.0*a0)/(a1+sqrt(a1*a1-4*a2*a0));
else
h=(-2.0*a0)/(a1-sqrt(a1*a1-4*a2*a0));
x4=x3+h;
f4=F(x4);
if(f4<=EPS)
{
printf("\n\nRoot By Muller'S Method\n\n");
printf("Root=%f\n",x4);
printf("\n");
}
else
{
x1=x2;
x2=x3;
x3=x4;
f1=f2;
f2=f3;
f3=f4;
goto begin;
}
}
float F(float x)
{
float f;
f=(x*x*x)+(2*x*x)+(10*x)-20;
return (f);
}

hey compiler is showing me the same error please help me out!!!!!

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:22:48 -0700

you need to protect t=pow(2,t) before calling it. You also might want to cast t into a double not an int for instance
double tmp=(double)t;
if(fabs(tmp)>1000.0)
return some_error_code;
tmp=pow(2.0,tmp);
if(fabs(tmp)<32000.0)
t=(int)tmp;
else
return some_other_type_of_error

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:24:38 -0700

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:26:29 -0700

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:39:36 -0700

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:41:25 -0700

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:43:25 -0700

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:51:13 -0700

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:53:07 -0700

Re: Floating point error in turbo c++

Mon, 04 Mar 2013 07:54:56 -0700