Though the power of any PC is depended upon all the parts of it if you consider over all the most important part of any microcomputer (PC)is the microprocessor. It is a chip playing significant role in the everyday functioning of industrialized societies.
We can define microprocessor as a programmable logic device that can be used to control process or to turn off /on devices or to process data as a computing unit of the PC.
The three basic parts of any microprocessor are -
1. ALU(Arithmetic Logic Unit)
2. CU(Control Unit)
3. MU(Memory Unit)
The microprocessor revolution began with the innovative and bold decision of logic design pioneered by Ted Hoff in 1969. During that time Intel was primarily in business of designing semiconductor chip. They had a contract from Japanese company "Busicom" to design a programmable calculator. Ted Hoff suggested a general purpose chip that could perform various logic functions based on some patterns of 1s and 0s. Later on Intel found that chip was capable of working in variety of fields and thus they coined the term microprocessor and released the chip as Intel 4004 in 1971. It was built by LSI technology having 2300 transistors and 640bytes of addressable memory with a clock speed of 108KHz. And the revolution begun.....
4004 microprocessor Busicom's Calculator