The history of computers began thousands of years ago with the abacus, used in China as an early counting device. The first programmable computer was invented in Germany in the 1930s, while the first digital commercial computer was the ENIAC, created in the 1940s. In the 1980s, Bill Gates and Steve Jobs drove the personal computer revolution by making computers more accessible and user-friendly through Microsoft and Apple. They established the foundations for how people interact with computers today.

1. History of computers. Where
did it all start?
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2. Lets take a trip down memory lane and look at the history of computers.
So let's get started.
You will be surprised to know that the history of computers actually started
thousands of years ago in China with a little device called the Abacus.
Yep, that little device that people often use as a toy for their babies to keep
them busy.
Well, actually, people used their fingers and stones to count with before the
abacus came. Imagine carrying a bunch of stones around to count with.
You already had to walk long distances in those days so carrying rocks
around for counting wasn't a good idea.
So, in a sense you could say that the abacus was sort of the first laptop.
The abacus wasn't really a computer, it was more a counting device or a
device to track numbers with. For instance, it was used to keep track of
sheep or keep inventory information on stock or food supplies. It was also
used to keep track of groups of items.
This device was so popular that it quickly spread to other countries and
some people still use it today.
Old Chinese abacus
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3. The first programmable computer was actually invented between 1936
and 1937 by a German guy called Konrad Zuse. He created the first
electrical binary programmable computer called the Z1. This computer
and design plans were unfortunately destroyed during the second world
war, but Konrad did develop later versions of the Z1 called the Z2 and
Z3.
The first digital commercial computer was called the ENIAC or
Electronic Numerical Integrator And Computer.
ENIAC Computer
Image courtesy of Computer History Museum.
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4. To be honest here, I think the whole PC or Personal Computer
revolution started with Bill Gates and Steve Jobs in the early eighties
and a page on the history of computers would not be complete without
the mention of these two guys.
Sure, there were computer firsts, but these guys made the computer
easily accessible to everybody.
Bill gates created Microsoft and convinced IBM or International
Business Machines Corporation to sell his operating system, DOS or
Disk operating System with every IBM PC sold. They sell a PC and Bill
sells a license. Now that's clever.
IBM thought that the real money is in hardware. Bill Gates thought it
was in software. Boy, was he right. It made him one of the richest men
in the world. Not bad for a guy who actually bought DOS from
someone else for $50000 and licensing it to IBM.
Steve Jobs, on the other hand, thought that the only way a PC should
work is if you develop the software and the hardware and selling it as a
complete package. Steve Jobs created a company called Apple and
developed the hardware and the software. Again, a clever idea which
also made him a very rich man.
Another thing that made Apple computers so popular was the fact that
the computers was actually nice to look at. Jobs also saw the potential
of a graphical interface and created the Apple Macintosh which was the
first successful commercial computer sold. 4

5. Depending on their processing powers, size and area of use, they
have been classified into various types. Based on the operational
principle, computers can be classified as analog and digital. Based
on their processing powers, they can be categorized as mainframe
and microcomputers. Based on the usage, they can be grouped
under desktop computers, laptops, tablets, netbooks, personal
digital assistants (PDAs) and even tiny wearable ones.
Basis of Classification
Operational Principle Size and Processing Power Use
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6. Based On Operational Principle
✦ Analog Computers: These are almost extinct today. These are
different from a digital computer because an analog computer can
perform several mathematical operations simultaneously. It uses
continuous variables for mathematical operations and utilizes
mechanical or electrical energy.
✦ Digital Computers: They use digital circuits and are designed to
operate on two states, namely bits 0 and 1. They are analogous to
states ON and OFF. Data on these computers is represented as a
series of 0s and 1s. Digital computers are suitable for complex
computation and have higher processing speeds. They are
programmable. Digital computers are either general purpose
computers or special purpose ones. General purpose computers, as
their name suggests, are designed for specific types of data
processing while general purpose computers are meant for general
use.
✦ Hybrid Computers: These computers are a combination of both
digital and analog computers. In this type of computers, the digital
segments perform process control by conversion of analog signals to
digital ones. 6

7. Analog Computer (Slide Rule)
Digital Computer
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8. Based On Size and Processing Power
✦ Mainframe Computers: Large organizations use mainframes
for highly critical applications such as bulk data processing and
ERP. Most of the mainframe computers have capacities to host
multiple operating systems and operate as a number of virtual
machines. They can substitute for several small servers.
✦ Microcomputers: A computer with a microprocessor and its
central processing unit is known as a microcomputer. They do not
occupy space as much as mainframes do. When supplemented
with a keyboard and a mouse, microcomputers can be called
personal computers. A monitor, a keyboard and other similar input-
output devices, computer memory in the form of RAM and a power
supply unit come packaged in a microcomputer. These computers
can fit on desks or tables and prove to be the best choice for
single-user tasks.
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9. Mainframe Computer
Microcomputer
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10. Based on Use
✦ Desktop Computers: A desktop computer is intended to be
used on a single location. The spare parts of a desktop computer
are readily available at relatively lower costs. Power consumption
is not as critical as that in laptops. Desktop computers are widely
popular for daily use in the workplace and households.
✦ Laptops: Similar in operation to desktop computers, laptop
computers are miniaturized and optimized for mobile use. Laptops
run on a single battery or an external adapter that charges the
computer batteries. They are enabled with an inbuilt keyboard,
touch pad acting as a mouse and a liquid crystal display. Their
portability and capacity to operate on battery power have proven
to be of great help to mobile users.
Desktop Computer Laptop
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11. ✦ Netbooks: They fall in the category of laptops, but are
inexpensive and relatively smaller in size. They had a smaller
feature set and lesser capacities in comparison to regular laptops,
at the time they came into the market. But with passing time,
netbooks too began featuring almost everything that notebooks
had. By the end of 2008, netbooks had begun to overtake
notebooks in terms of market share and sales.
✦ Personal Digital Assistants (PDAs): It is a handheld computer
and popularly known as a palmtop. It has a touch screen and a
memory card for storage of data. PDAs can also be used as
portable audio players, web browsers and smartphones. Most of
them can access the Internet by means of Bluetooth or Wi-Fi
communication.
Netbook PDA
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12. ✦ Minicomputers: In terms of size and processing capacity,
minicomputers lie in between mainframes and microcomputers.
Minicomputers are also called mid-range systems or workstations. The
term began to be popularly used in the 1960s to refer to relatively
smaller third generation computers. They took up the space that would
be needed for a refrigerator or two and used transistor and core
memory technologies. The 12-bit PDP-8 minicomputer of the Digital
Equipment Corporation was the first successful minicomputer.
✦ Servers: They are computers designed to provide services to client
machines in a computer network. They have larger storage capacities
and powerful processors. Running on them are programs that serve
client requests and allocate resources like memory and time to client
machines. Usually they are very large in size, as they have large
processors and many hard drives. They are designed to be fail-safe
and resistant to crash.
✦ Supercomputers: The highly calculation-intensive tasks can be
effectively performed by means of supercomputers. Quantum physics,
mechanics, weather forecasting, molecular theory are best studied by
means of supercomputers. Their ability of parallel processing and their
well-designed memory hierarchy give the supercomputers, large
transaction processing powers.
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13. Server
Supercomputer
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14. ✦ Wearable Computers: A record-setting step in the evolution of
computers was the creation of wearable computers. These
computers can be worn on the body and are often used in the
study of behavior modeling and human health. Military and
health professionals have incorporated wearable computers into
their daily routine, as a part of such studies. When the users'
hands and sensory organs are engaged in other activities,
wearable computers are of great help in tracking human actions.
Wearable computers do not have to be turned on and off and
remain in operation without user intervention.
✦ Tablets: Tablets are mobile computers that are very handy to
use. They use the touch screen technology. Tablets come with an
onscreen keyboard or use a stylus or a digital pen. Apple's iPad
redefined the class of tablets.
Wearable Computer
Tablet
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