convert integer to single float IEEE 754

to_float.c

#include <stdio.h>
#include <stdlib.h>

int to_float( int number )
{
	int flt = 0;

	if ( number < 0 )
	{
		number = -number;
		flt |= ( 1 << 31 );
	}

	int lz = 0;
	for ( int i = 0; i < 32; ++i )
	{
		if ( number & ( 1 << ( 32 - i - 1 ) ) )
			break;
		++lz;
	}
	int exp = 32 - lz - 1;
	for ( int i = 0; i < lz; ++i )
	{
		int bit = ( number & ( 1 << ( 32 - i - lz - 1 ) ) ) == 0 ? 0 : 1;
		flt |= ( bit << ( 32 - i - 1 - 8 ) );
	}
	flt &= ~( 1 << 23 ); // clear leading 1
	flt |= ( ( ( exp + 127 ) & 0xff ) << 23 );
	return flt;
}

int main( int argc, char** argv )
{
	int n = atoi( argv[1] );
	int f = to_float( n );
	printf( "n = %d, as_float = %d, %f\n", n, f, *(float*)&f );
	return 0;
}