Some info on the history of the microchip. When it all started.
In 1969, Nippon Calculating Machine Corporation requested that Intel design 12 custom chips for its new Busicom 141-PF printing calculator. Instead of creating a dozen custom chips specifically for the calculator, Intel’s engineers proposed a new design: a family of just four chips, including one that could be programmed for use in a variety of products.
The set of four chips was called the MCS-4. It included a central processing unit (CPU) chip—the 4004, a supporting read-only memory (ROM) chip for the custom applications programs, a random-access memory (RAM) chip for processing data, and a shift-register chip for the input/output (I/O) port. Intel delivered the four chips and Busicom went on to sell some 100,000 calculators.
Intel offered Busicom a lower price for the chips in return for securing the rights to the microprocessor design and the rights to market it for non-calculator applications, allowing the Intel 4004 microprocessor to be advertised in the November 15, 1971 issue of Electronic News. It’s then that the Intel 4004 became the first general-purpose microprocessor on the market—a “building block” that engineers could purchase and then customize with software to perform different functions in a wide variety of electronic devices.
Source: Intel Museum website