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Floating Point

How can I deny a number floating point without utilizat some mathematical operation?

How can I take the first 8 bits of the number floating point, those but significant (MSB) or the bit but significant of the number type floating point?

Parents

0 Jon Young over 24 years ago

Here is a routine to print the parts of a normalized float ( except for 0.0 or -0.0 ).

#include <stdio.h>
#include "AT89X55.H" // to define TI

typedef unsigned char BYTE;
typedef unsigned int  WORD;
typedef unsigned long DWORD;

void PrintFloat( float TheFloat )
{
  union
  {
    struct
    {
      float Float;
    } Whole;

    struct
    {
      //@Float+0
      BYTE Exp1         :7; //bits 6-0
      BYTE Sign         :1; //bit 7

      //@Float+1
      BYTE Significand2 :7; //bits 6-0
      BYTE Exp0         :1; //bits 7

      //@Float+2
      BYTE Significand1 :8; //bits 7-0

      //@Float+3
      BYTE Significand0 :8; //bits 7-0
    } Parts;
    
  } Float;

  Float.Whole.Float = TheFloat;

  printf( "Float             = %#e\n",  (double)TheFloat );
  printf( "Sign              = %#i\n",  (int)Float.Parts.Sign );
  printf( "Exp Base 2        = %#i\n" , ( (int)Float.Parts.Exp1<<1 | (int)Float.Parts.Exp0 )  - 127);
  printf( "Mantissa Base 2   = %#lX\n" , 0x800000 | ( (DWORD)Float.Parts.Significand2 ) << 16
                                                  | ( (DWORD)Float.Parts.Significand1 ) << 8
                                                  | ( (DWORD)Float.Parts.Significand0 ) );
  printf( "\n" );
}


void main(void)
{
  TI = 1;  //to get debugger to print to serial window

  PrintFloat( -2.3456E10 );
  PrintFloat( 0.0 );  //note!! 0.0 is all zeros plus a sign bit

  while( 1 )
    ;
}

Reply

0 Jon Young over 24 years ago

Here is a routine to print the parts of a normalized float ( except for 0.0 or -0.0 ).

#include <stdio.h>
#include "AT89X55.H" // to define TI

typedef unsigned char BYTE;
typedef unsigned int  WORD;
typedef unsigned long DWORD;

void PrintFloat( float TheFloat )
{
  union
  {
    struct
    {
      float Float;
    } Whole;

    struct
    {
      //@Float+0
      BYTE Exp1         :7; //bits 6-0
      BYTE Sign         :1; //bit 7

      //@Float+1
      BYTE Significand2 :7; //bits 6-0
      BYTE Exp0         :1; //bits 7

      //@Float+2
      BYTE Significand1 :8; //bits 7-0

      //@Float+3
      BYTE Significand0 :8; //bits 7-0
    } Parts;
    
  } Float;

  Float.Whole.Float = TheFloat;

  printf( "Float             = %#e\n",  (double)TheFloat );
  printf( "Sign              = %#i\n",  (int)Float.Parts.Sign );
  printf( "Exp Base 2        = %#i\n" , ( (int)Float.Parts.Exp1<<1 | (int)Float.Parts.Exp0 )  - 127);
  printf( "Mantissa Base 2   = %#lX\n" , 0x800000 | ( (DWORD)Float.Parts.Significand2 ) << 16
                                                  | ( (DWORD)Float.Parts.Significand1 ) << 8
                                                  | ( (DWORD)Float.Parts.Significand0 ) );
  printf( "\n" );
}


void main(void)
{
  TI = 1;  //to get debugger to print to serial window

  PrintFloat( -2.3456E10 );
  PrintFloat( 0.0 );  //note!! 0.0 is all zeros plus a sign bit

  while( 1 )
    ;
}

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