A computer is an electronic device that manipulates information or data. It has the ability to store, retrieve, and process data. Nowadays, a computer can be used to type documents, send email, play games, and browse the Web. It can also be used to edit or create spreadsheets, presentations, and even videos. But the evolution of this complex system started around 1940 with the first Generation of Computer and evolving ever since.
"Generation" in computer talk provides a framework for the growth of computer industry based on key technologies developed. Orijinally, it was used to distinguish between hardware technologies but was later extended to include both hardware and software technologies.
The custom of referring to computer era in terms of generations came into wide use only after 1964. There are totally five computer generations known until today. Below we describe each generation along with its identifying characteristics. Although there is some overlap between different generations, the approximate period shown against each is normally accepted.
In the description below, you will give across several new terminologies. Subsequent chapters will deal with these terminologies in detail. The idea here it to provide an overview of the major developments and technologies during the five generations of computers and not to explain them in detail. Hence, this section provides an overview of what all you are going to learn in this chapter...
First generation: Vacuum tubes (left). Mid 1940s, beginning with ENIAC. IBM pioneered the arrangment of vacuum tubes in pluggable modules such as the one shown in the photo. The IBM 650 (1953) was a first-generation computer, as were the pioneering IBM one-off SSEC (1948) and NORC (1954), both built by Columbia University's Watson Lab.
Second generation: Transistors (right). 1956. The era of miniaturization begins. Transistors are much smaller than vacuum tubes, draw less power, and generate less heat. Discrete transistors are soldered to circuit boards like the one shown, with interconnections accomplished by stencil-screened conductive patterns on the reverse side. The IBM 7090 was a second-generation computer.
Third generation: Integrated circuits (foreground), silicon chips contain multiple transistors. 1964. A pioneering example is the ACPX module used in the IBM 360/91, which, by stacking layers of silicon over a ceramic substrate, accommodated over 20 transistors per chip; the chips could be packed together onto a circuit board to achieve unheard-of logic densities. The IBM 360/91 was a hybrid second- and third-generation computer.