The first integrated circuits (IC) appeared toward the end of the sixties. They allowed  to realize numerous transistors and relative connections on an only silicon chip. Their use in computers produced further reductions in price and size of machines and a meaningful increase in their functionality. The microprocessor appared in the half of the seventies, when Large Staircases Integration circuits, (LSI) and then Very Large Staircases integration circuits, (VLSI), whereimplemented. They contained million of interconnected transistors, realized on an only silicon chip. The computers of the seventies, could recognize generally groups of eight states,; that is to say/they could treat eight binary digits (binary digits or bit) for every cycle. A group of eight bits constitutes a byte; a byte can assume 28=256 possible configurations of states ON and OFF (1 or 0). Each of these configurations can represent an instruction, one part of it or a datum suck as a number, a character or a graphic symbol. The combination 11010010, can represent for instance a binary numerical datum or an istruction, as "compare the content  register with that of a   memory cell..A computer that processes information  contemporary groups of 8 bits computer is said an 8 bit computer. Such designation can refer either is to the  word length(basic unity of processed information) of the microprocessor or, more commonly, to the number of bits moved with a single operation along the data bus, that is the path connection long which information travely from or towards the microprocessor. Therefore, an 8 bit microprocessor has length of word of 8 bits, or of a byte; a bus-data to 8 bits it has 8 lines, therefore it carries information through the system in contemporary groups of 8 bits. Equally, a  16 bit computer  processes information in contemporary groups of 16 bits and a 32 bit processes  a group of 32 bits at each step.
The development of computers able to treat in block combinations of 16, 32 or 64 bits increased the processing speed. The whole of all the combinations of bits that a computer is able to recognize as instructions, is said instruction set . Both these characteristics  are improving in  modern computers.