Computer History: Classification of
Generations of Computers

ALFRED AMUNO

FEB 10, 2023 5:26 PM EST
Transistors and integrated circuit chips have become smaller in each succeeding
generation of computers.
5 Generations of Computers
Generations of computers have seen changes based on evolving technologies. With
each new generation, computer circuitry, size, and parts have been miniaturized, the
processing and speed doubled, memory got larger, and usability and reliability
improved.
Note that the timeline specified for each generation is tentative and not definite. The
generations are actually based on evolving chip technology rather than any particular
time frame.
The five generations of computers are characterized by the electrical current flowing
through the processing mechanisms listed below:

The first within vacuum tubes

The second within transistors

The third within integrated circuits

The fourth within microprocessor chips

The fifth unveiled smart devices capable of artificial intelligence
First Generation of Computers: 1940s-1950s: (Vacuum
Tubes and Plugboards)
First-generation computers were actually the first general-purpose and true digital
computers. They came in time to replace the electromechanical systems, which were
way too slow for assigned tasks.
One task was the need by the US Army to have machines capable of computing artillery
firing tables fast enough. The existing ones took almost two days. When completed, the
new machines computed this table data in seconds. Fortunately or unfortunately, they
became available only after the end of World War II in 1946.
Vacuum tubes were used in the 1st computer generation.
Dpbsmith
First-generation computers used vacuum tubes for amplification and switching
purposes. The tubes were made of sealed glass containers the size of light bulbs. The
sealed glass allowed current to flow wirelessly from the filaments to metal plates. And
because there were no moving parts in the system, the flow amplified current to enable
the computer to manipulate assigned tasks. Vacuum tubes also started and ended the
circuitry by switching on and off when turned on or off.
Besides boasting thousands of resisters and capacitors, these computers would use
anything up to and over 17,000 vacuum tubes, which meant computer installations
covered entire rooms!
Input and output were done using punch cards, magnetic drums, typewriters, and punch
card readers. Initially, technicians manually perforated the cards with holes. This was
later done using computers.
Interfacing with first gen systems was done using plugboards and machine language.
The technicians wired up electrical circuits by connecting numerous cables to
plugboards.
Then they slotted specified punched cards into them and waited for hours for some form
of computation while hoping every one of the thousands of vacuum tubes lasted the
distance, lest they went through the procedure again.
A record machine plugboard for IBM 1401
By ArnoldReinhold
These machines were intended for low-level operations, and thus programming was
done using only binary digits 0s and 1s. The systems could solve only one problem at a
time. Assembly language and operating system software were nonexistent.
One of the most outstanding computers in this era was The ENIAC (Electronic
Numerical Integrator and Computer), which was designed and built by Engineers John
W. Mauchly and J. Presper Eckert of the University of Pennsylvania. Its assembly was
done by a team of fifty men.
It was 1000 times faster than the previous electromechanical computers but was a little
slow when it came to re-programming.
Among many things, The ENIAC was used to study the feasibility of thermonuclear
weaponry, the firing of ballistic artillery and engine thermal ignition, and elsewhere, for
weather predictions.
The left side of The ENIAC computer
by%20u.s.%20army
These systems were enormous in size and occupied entire rooms while using lots of
electric power. This made them generate unbearable heat.
A list of popular first generation computers:

The ENIAC (1946)

EDSAC (1949)

EDVAC (1950)

UNIVAC I (1951)
The UNIVAC (Universal Automatic Computer), still by Engineers John W. Mauchly and
J. Presper Eckert, was the first in the same era to be designed for commercial rather
than military use. It manipulated both the alphabet and numbers fairly well and was
used by USA Census Bureau to enumerate the general population. It was later used to
manipulate payrolls, records, company sales, and even predicted presidential election
results in 1952.
Unlike the over 17,000 vacuum tubes in The ENIAC, UNIVAC I used slightly over 5,000
vacuum tubes. It was also half the size of its predecessor and sold over 46 units.
UNIVAC as exhibited in the Vienna Technical Museum
Stefan Kögl
Characteristics of 1st Generation Computers
They:

Used vacuum tubes for circuitry

Electron emitting metal in vacuum tubes burned out easily

Used magnetic drums for memory

Were huge, slow, expensive, and many times undependable

Were expensive to operate

Were power hungry

Generated a lot of heat which would make them malfunction

Solved one problem at a time

Used input based on punched cards

Had their outputs displayed in print outs

Used magnetic tapes

Used machine language

Had limited primary memory

Were programming only in machine language
Second Generation of Computers: 1950s-1960s:
(Transistors and Batch Filing)
These were computers which used transistors instead of vacuum tubes. They were
better than their predecessors in many ways because of apparent small size, speed,
and cheaper cost.
Transistors are more or less the building blocks of any microchip out there, and also,
more reliable, energy efficient and capable of conducting electricity faster and better.
The transistor was used in the 2nd computer generation.
Willtron
Just like vacuum tubes, transistors are switches or electronic gates used to amplify or
control current, or switch electric signals on and off. They are called semiconductors
because they contain elements which lie between conductors and insulators.
Transistor semiconductors were invented at Bell Laboratories in 1947 by scientists
William Shockley, John Bardeen and Walter Brattain, but did not see the day of light
until mid-1950s.
Second generation computers saw advancement in data input and output procedures.
Initially, these processes were similar to the last models of 1st gen computers. They
were tedious because they involved multiple personnel carrying punched cards from
room to room.
To speed up the process, the batch system was conjured up and implemented. It
involved collecting multiple data jobs into multiple punched cards and feeding them into
single magnetic tapes using a fairly smaller and inexpensive system. The IBM-1401 was
one such computer. Processing, on the other hand, was done using a more powerful
system like the IBM 7094.
When data manipulation was complete, the files were transferred back to a magnetic
tape. To do this efficiently, IBM's operating system for IBM-7094 system and Fortran
Monitor System were used. These were the harbingers of operating system software to
come.
Using a smaller system again, say IBM-1401, the data was printed out to multiple punch
cards as output.
IBM 1401 computer with one circuit card access drawer opened, on display at the
Computer History Museum
By ArnoldReinhold
Besides the development of operating systems software, other commercial applications
were also hitting the 'shelves'. This was probably due to the overall upgrade from
restrictive binary based machine code to languages that wholly supported symbolic and
alphanumeric coding. Programmers could now write in assemblers and high-level
languages like FORTRAN, COBOL, SNOWBALL, and BASIC in 1964.
Punched card as part of a FORTRAN IV program
Characteristics of 2nd Gen Computers
They:

Used transistors

Faster and more reliable than first generation systems

Were slightly smaller, cheaper, faster

Generated heat though a little less

Still relied on punch cards and printouts for input/output

Allowed assembly and high-level languages

Stored data in magnetic media

Were still costly

Needed air conditioning

Introduced assembly language and operating system software
Operator's console for IBM 7094 at the Computer History Museum
By ArnoldReinhold
The early mainframes and supercomputers were just some of the machines which took
advantage of transistors. The UNIVAC LARC mainframe from Sperry Rand (1960) and
IBM-7030 Stretch supercomputer (1961), and CDC 6600 mainframe (1963) were
examples of these systems.
Other examples of 2nd Gen computers:

IBM-7000

CDC 3000 series

UNIVAC 1107

IBM-7094

MARK III

Honeywell 400
Third Generation of Computers: 1960-1970s (Integrated
Circuits and Multi-Programming)
3rd generation computers used the integrated circuit (IC) microchip instead of
transistors. The semiconductor IC packed a huge number of transistors, capacitors,
diodes, and rectifiers onto a single germanium or silicon. These were then printed on
separate parts of a printed circuit board.
The implementation of these computers was also in line with Moore's Law (1965), which
observed that transistor size was shrinking so fast, that double the number would fit into
new microchips every two years for 10 years to come.
He readjusted this exponential growth after ten years to every five years in 1975.
Integrated circuit on microchip
The IC sought to solve the cumbersome procedures that went into designing the
transistor circuitry. The manual interconnection of capacitors, diodes, and rectifiers in
transistors was time-consuming and not completely reliable.
Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Corporation separately
discovered the benefits of integrated circuits in 1958 and 1959, respectively. Kilby built
his IC onto germanium whereas Noyce built one onto a silicon chip.
The first systems to use the IC was the IBM 360, which was packed with the muscle to
handle both commercial and scientific assignments.
Jack Kilby's IC chip
Besides the reduction in cost, the speed and performance of any one computer
increased tremendously after placing multiple transistors on a single chip. Since its
invention, the IC speed doubled every two years, shrinking both the size and cost of
computers even further.
Almost all electronic devices today use some form of integrated circuits placed on
printed circuit boards.
The IC circuitry aside, the interaction with computers improved. Instead of punched
cards printouts, keyboards and better input peripherals were used to input data which
were displayed for output through visual display units.
Computers now used operating system software to manage computer hardware and
resources. This allowed systems to run different applications at a time. This was
because of centralized applications that monitored memory distribution.
Computers became accessible to the mass audience because of size and fair costing.
This generation also ushered in the concept of 'computer family' which challenged
manufacturers to come up with computer components that were compatible with other
systems.
A neat-looking IBM 370 mainframe released in 1970
By Bobo11
Characteristics of 3rd Gen Computers
They:

Used ICs

Used parallel processing

Were slightly smaller, cheaper, faster

Used motherboards

Data was input using keyboards

Output was visualized on the monitors

Used operating systems, thus permitting multitasking

Simplified programming languages i.e. BASIC
The next generation of mainframes and supercomputers took advantage of integrated
circuits (IC). The Scientific Data Systems Sigma 7 (1966) mainframe, and IBM-360
(1964) and CDC 8600 supercomputers (1969) were examples of these systems.
Other examples of third generation computers:

IBM-360

Personal Data Processor (PDP)

IBM-370
IBM 360 Mainframe in the German Museum
By Wolfgang Manousek
Fourth Generation of Computers: 1970s to Present (The
Microprocessor, OS, and GUI)
The birth of the microprocessor was at the same time the birth of the microcomputer. It
was also in line to fulfill Moore's law which predicted exponential growth in transistor
and microchips starting in 1965. This generation is instrumental in ushering in diverse
devices. The 2nd generation computers which began in 1971 are those in use today.
Intel, through its engineers Ted Hoff, Federico Faggin and Stan Mazor In November
1971, introduced the world's first single chip microprocessor, the Intel 4004. It boasted
of 2300 transistors and measured 1/8" by 1/16".
What in the first generation filled an entire room could now fitted in the palm of the hand.
On its own, new microchip was as powerful as The ENIAC computer from 1946. It also
merged most of the functions that charged a computer like central processing unit,
memory, input and output controls.
The Intel C4004 microprocessor initiated the 4th computer generation.
By Peter1912
Manufacturers soon started integrating these microchips in their new computers.
In 1973, the Xerox Alto computer from PARC was released silently. It was a true
personal computer and featured an Ethernet port, a mouse, and a bit-mapped graphical
user interface, the first of its kind.
The last feature was motivation to Apple computers to build one of a kind. Xerox Alto
was powered by a 16bit TI SN74S181N ALU chip from Texas Instruments.
Xerox Alto is arguably the first PC from 1973. It was powered by a TI SN74S181N ALU
chip from Texas Instruments.
By Maksym Kozlenko
Challenged by the Xerox Alto, serious staff began in 1974 when Intel came up with a
general purpose 8-bit microprocessor it named 8808. It sought for, and asked Gary
Kildall, a consultant, to write an operating system for its new baby. This led to the diskbased operating system software known as Control Program for Microcomputers
(CPM).
In 1981, International Business Machine introduced its first computer for the home
which ran the 4004 processor. It was known as IBM PC, with PC standing for personal
computer. They partnered with Bill Gates who bought Disk Operating System from
Seattle Computer Product and had it distributed with IBM's new computer.
The original IBM PC in 1981
By User:FA2010
The IBM PC architecture became the de facto market standard model, which other PC
makers emulated.
Apple under Steve jobs, changed the software game when it released the Apple
Macintosh computer with an improved GUI (Graphical User Interface) in 1984, using the
interface idea learned from Xerox PARC.
Remember that both Control Program for Microcomputer and Disk Operating System
were command-line based operating systems which the user to interface with the
computer using the keyboard.
The Apple Macintosh of 1984
By Álvaro Ibáñez
Following the success of Apple's GUI, Microsoft too integrated a shell version of
Windows in the DOS version of 1985. Windows was used like this for the next 10 years
until it was reinvented as Windows 95. This was a true operating system software
complete with all the right utilities.
Ubuntu running MS Windows 3.11 under VBox
By User230792
While software became commonplace and corporations began charging money for it, a
new movement of programmers started Linux in 1991. Led by Linux Torvalds, they
pioneered a free open source operating system project called Linux.
Besides Linux, other open source operating systems and free software were distributed
to cater for office, networking and home computers.
Examples of open source and free software:

Ubuntu OS

Mozilla Firefox browser

Open Office

MySQL

VLC media player
Through the 1980s and 2000s, personal computers, and desktops, in particular,
became commonplace. They were cheap and installed in offices, schools and homes.
Software that ran on these computers also became readily available for small money or
for free.
Examples of popular personal computer categories:

Desktops

All-in-one

Laptops

Workstations

Nettops

Tablets

Smartphones
A desktop computer
Soon, microprocessors moved out of the reserve of desktop computers into other
platforms in businesses and homes. First was the laptop, followed by tablets and
smartphones, consoles, embedded systems, and smart cards. These devices increased
the need to use the internet while on the move.
The proliferation of mobile computing device soon fought off the dominance of
desktops. According to ComScore in the publication Mobile’s Hierarchy of Needs of
March 2017, mobiles accounted for 60% of all digital minutes across the world.
A kid using an iPad tablet
Characteristics of 4th Gen Computers
They:

Used CPUs which contained thousands of transistors

Were much smaller and fitted on a desktops, laps and palms

Used a mouse

Were used in networks

Were cheap

Had GUI

Were very fast

Register over 19 billion transistors in high-end microprocessors (Compare with 2,300 in
Intel 4004)
The fourth generation of mainframes and supercomputers evolved to powerful systems:

IBM z9 (2005), z10 (2008) and z13 (2015) are examples of mainframes.

Cray 1 (1975), Fugitsu K (2011), Titan (2013), Sunway TaihuLight (2016) are examples
of supercomputers.
The Cray-1 supercomputer of 1975
By Rama
Fifth Generation of Computers: The Present and The
Future
Fifth generation computing is built on technological advancement gained in the previous
computer generations. It is meant to headline the 4th Industrial Revolution (4IR).
The implementation is designed to improve human and machine interaction by
harnessing human intelligence and taking advantage of the large data that has
accumulated since the dawn of the digital age.
It is viewed as the cyber-physical system and arises from the theory, concept and
implementation of artificial intelligence (AI) and machine learning (ML). AI and ML may
not be the same but are used interchangeably to mean the science of crafting devices
and programs which are intelligent enough to interact with humans, other computers,
the environment, and programs, by mining big data to achieve set goals.
The proliferation of computing devices with the possibility they can self-learn, respond
and interact in normal and probably different ways, based on acquired experience and
environment, has also given momentum to the Internet of Things (IoT) concept.
At their peak and with the right algorithms, computers will probably exhibit and process
high levels of deep learning, which humans can learn from too.
Many AI projects are already being implemented while others are still in developmental
stages. Pioneers in accelerating AI include Google, Amazon, Microsoft, Apple,
Facebook, and Tesla.
The initial implementations are now seen on smart home devices which are meant to
automate and integrate activities in the house though audio/visual devices, and selfdrive cars which are already gracing the roads.
Coral (red) version of the Google Home Mini smart speaker
By Mrschimpf
The larger goals in AI is to indulge devices to:

Understand natural language

Recognize human speech

See the world in three-dimensional perspective

Play interactive games

Implement expert input in medical and other complex fields

Exercise heuristic classification analysis

Implement neural networks
Other areas which are geared towards making AI possible are developments in:

Quantum computing

Parallel processing
Ongoing AI projects:

Virtual personal assistants e.g. Siri, Google Now and Braina.

Smart cars e.g. Tesla's autopilot cars and Google's self-driving cars.

News generation tools like Wordsmith are used by Yahoo and Fox to generate news
snippets.

Computer Aided Diagnosis for detection of cancer.
This article is accurate and true to the best of the author’s knowledge. Content is for
informational or entertainment purposes only and does not substitute for personal
counsel or professional advice in business, financial, legal, or technical matters.