Since the 80x86 works with groups of eight bits, we find it much easier to zero extend all binary numbers to some multiple of four or eight bits.

For example, 102 which is 2 in decimal will be converted to 0010 or 0000 0010.

In any case, a space is placed between every four digits to make it easier on the eyes (like commas between every decimal thousand), and to simplify converting to and from hexadecimal since each hexadecimal digit (i.e. F) is made up of four binary digits (i.e. 1111).