0nnnnnnn

If the first byte (8 bits) of an address is a class A address, it will have a 0 in the first bit. Since this 8 bit number is a binary number, each of the next 7 bits would be a 1 or a 0. That means the largest possible binary number for that first byte would be 01111111 or 127 in decimal (0+64+32+16+8+4+2+1). The smallest possible binary number for that first byte would be 00000000 or 0 in decimal (0+0+0+0+0+0+0+0).