Computer generations

A common way of showing the evolution of computers is to resort to the so-called generations, temporary periods of computer development. One generation begins with a disruptive technological advance and ends when another advance appears surpassing the first one and begging a new generation.

Traditionally there are 5 generations, although there are those who already speak of 6. I in principle continue speaking of 5 although I mention the technological advances that are already here and will surely end up closing the fifth generation and giving way to the sixth. These advances are Artificial Intelligence and parallel processing.

In my classes I use the slide below to introduce the generations of computers:

Computer generations

First generation (1940-1955)

The technology that led to this generation of computers was that of vacuum valves, also known as electronic valves. This component was already being used in other devices such as radio or television.

To understand the progress that it brought about, it is necessary to explain what computers were like before this generation. They were electronic and analogic computers, made up of a bunch of electronic circuits, connected to wiring panels. To prepare these computers for a task, their circuits were physically connected using the wiring panels, in such a way that every time we wanted to change the task (which could be equivalent to changing programs on a modern computer) we had to rewire the entire computer, practically rebuilding it from scratch. In short, a big pain that could be avoided with the use of vacuum valves.

These valves have a characteristic that made them ideal for use in computers and that was that they could switch the electrical signal. For us to get started, it is as if we have a switch that we can open or close, disconnecting or connecting circuits. Quite a step forward for the time, it was no longer going to be necessary to wire the computer manually connecting the circuits, as if it were an old telephone exchange in which the operator connected you with the line of the person with whom you asked to speak. Vacuum valves were going to make this unnecessary and start programming computers instead of wiring them. By the way, it was programmed in machine language, the lowest possible level.

There are many very well know names from this generation that I find it difficult not to name, such as the ENIAC computer or the great Alan Turing, better known for deciphering the Nazi Enigma code or for his famous test to discriminate whether a machine is intelligent or not. In any case, in my classes, I focus on the technology that each generation fosters since I understand what needs to be explained. For the exciting history of computers, I usually link to videos that I think are good and educational. Here’s one: computer history video

Second generation (1956-1964)

The transistor came to replace vacuum valves, ending the first generation of computers and beginning the second.

Without going into excessive detail, the transistor is a semiconductor component that can be used as a switch, connecting or disconnecting circuits. In other words, it fulfils the same function as the vacuum valve but with two very important improvements: it consumes much less electricity and is significantly smaller. These two characteristics made second-generation computers consume much less power and were smaller than first-generation computers.

In addition, in this generation, high-level languages ​​also make their appearance, closer to the language of the human being than the machine languages ​​of the first generation. For example, to add two numbers in a program, it would have to send the “add” instruction to the CPU. Well, in machine code that instruction could be something like this: “10101011”, while in high-level languages it would be a command that is easier to understand, for example, “SUM”.

Third generation (1965-1971)

And what was the disruptive innovation that ended the second generation and gave way to the third? Well, it was the appearance of integrated circuits.

An integrated circuit is made of semiconductor material and integrates many components to form an electrical circuit. Among these components were a multitude of transistors that we remember are also made of semiconductor material. Therefore, within an integrated circuit or chip, we have many transistors in a very small space with lower manufacturing costs. All these characteristics made the computers of the third generation had:

  • Greater processing capacity
  • Smaller size
  • And they were cheaper

Fourth generation (1972-1982)

The arrival of the fourth generation of computers is not driven by disruption, but by improvements in circuit integration, which lead to two changes in computers that I think should be mentioned:

  • The appearance of the CPU, an integrated circuit that brings together several of the basic components for computing.
  • The development of silicon semiconductor memories, “memory chips”.

It should also be in mind that at this time is when personal computers or PCs appear.

Fifth generation (1983-…)

This generation is associated with the extreme improvement of circuit integration technologies. We refer to these by their acronym in English: VLSI (Very Large Scale Integration).

In reality, what we get is many more transistors in a very small space, which means more computing power and more miniaturization.

This generation is also known for the rise of the laptop.

Sixth generation ???

Some say that we are already in the sixth generation. The technological innovations that would give way to this new generation would be the use of artificial intelligence and parallel processing. Thanks to these two innovations, computers would be able to interact with humans and learn.

In any case, it is not relevant if we are already in a sixth generation or not, what is important is to know both technological improvements. I do not think that the rise of artificial intelligence justifies a new generation of computers, this boom has been possible thanks to the increase in computing and storage capacity. As for parallel processing, perhaps it could be argued as an innovation to enter a new generation, taking into account innovations in computer architecture.

The way I see it, the next truly disruptive innovation that will bring about a new paradigm in computing will be the quantum computer. These already exist but are still restricted to a very reduced environment, although companies like IBM are beginning to make them available to mortals, good for IBM!


This post is part of the collection “Computer Architecture” that reproduces the class notes that I use to teach the subject at ESIC. You can see the index of this collection here.