Just need 5 bits to differentiate symbols on 7seg display

You don’t need all 7 bits to differentiate symbols on 7 segments display.

I discovered it when I saw this project:
http://biphenyl.org/blog/?p=14

This guy soldered only few wires to read data from a breathalyzer, independently this other guy figure out we need only 5 bits to differentiate all symbols:
http://www.cibomahto.com/2008/02/how-many-unique-bits-in-a-seven-segment-display/

He wrote a python program to get the result. Then I converted it to C language:

#include stdio /* arrggg wordpress shit */
/*
0bX1111111 = 0bXGFEDCBA
*/

unsigned char digits[10] = {0b00111111,
			0b00000110,
			0b01011011,
			0b01001111,
			0b01100110,
			0b01101101,
			0b01111101,
			0b00000111,
			0b01111111,
			0b01101111};

void ptop(int i, unsigned char mask){
	unsigned char dig = digits[i] & mask;

	printf(" ");
	if (dig & 0b1)
		printf("_");
	else
		printf(" ");
	printf("   ");
}

void pmid(int i, unsigned char mask){
	unsigned char dig = digits[i] & mask;

	if (dig & 0b100000)
		printf("|");
	else
		printf(" ");

	if (dig & 0b1000000)
		printf("_");
	else
		printf(" ");

	if (dig & 0b000010)
		printf("|");
	else
		printf(" ");
	printf("  ");
}

void pbtm(int i, unsigned char mask){
	unsigned char dig = digits[i] & mask;

	if (dig & 0b10000)
		printf("|");
	else
		printf(" ");

	if (dig & 0b1000)
		printf("_");
	else
		printf(" ");

	if (dig & 0b100)
		printf("|");
	else
		printf(" ");
	printf("  ");
}

void printdigit(unsigned char mask)
{
	int i;
	for (i = 0; i < 10; i++)
		ptop(i, mask);
	printf("\n");
	for (i = 0; i < 10; i++)
		pmid(i, mask);
	printf("\n");
	for (i = 0; i < 10; i++)
		pbtm(i, mask);
	printf("\n");
	
}

int stillUnique(unsigned char mask)
{
	unsigned i, j;
	for (i = 0; i < 10; i++)
		for (j=i+1; j < 10; j++)
			if ((digits[i] & mask) == (digits[j] & mask))
				return 0;
	return 1;
	
}

int main ()

{

	unsigned char i;

	for (i = 0; i < 128; i++){
		if(stillUnique(i)){
			printf("Funcionou para %i\n", i);
			printdigit(i);
			printf("\n\n");
		}
	}

}