ENIAC was amongst the first computing system designed in the 1940s. In size, it was equal to the size of 3-4 double decker buses. With over 18,000 buzzing electronic switches called vaccum tubes it was no where close in computing abilities as compared to a Laptop in the modern times. You must be wondering, how we were able to squeeze down all the electonic circuits into smaller and smaller packages to the modern design where laptops are mere fraction of inches thick and very lightweight. The invention of Integrated Circuits in 1958 made it all possible.
Open up a Television or a Radio, and you will see a green colored board occupying most of the space inside, it is the Printed Circuit Board. It looks like a street map, with small electronic components(such as resistors and capacitors) in place of the buildings and printed copper connections linking them together like miniature metal streets.
Such circuit boards are fine in small appliances like this, but for a complex computing devices like a computer, it is impossible without the board being a couple of hundered square feets in size.
Simplest of computer requires about eight electronic switches to store a single byte(character) of information. So if you plan to build a simple computer with enough memeory to store this paragraph, which has about 450 characters, so it would require 450 x 8, about 3600 electronic switches. Considering the vaccum tubes used in the early 1940s, which were of the size of a human thumb, you will end up building a large, power hungry monster.
In 1947, with the invention of transistors, which were a fraction the size of the vaccum tubes and comsumed less power, using transistors for computations became easier, but still the complex circuits were not easy to handle.
The invention of Integrated Circuits in 1958, changed the game. The concept was to take the whole circuit, with all its components and the connections between them, and recreate the whole thing in microscopically tiny form on the surface of a piece of silicon.
Jack Kilby and Robert Noyce invented the Integrated Circuit at the same time. How incredible this is, two men, invent the same technology, at the same time, while not knowing each other.
In 1968, Robert Noyce co-founded Intel Electronics company which is still the global market leader in IC manufacturing, research and development.
An integrated circuit (also called an IC or just a chip) is a complete electronic circuit consisting of more than one individual components such as transistors, diodes, resistors, capacitors, and the conductive pathways that connect all the components, all made from a single piece of silicon crystal.