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Classification of Computers by Analog and Digital Signal Processing

Alfred is a long-time teacher and computer enthusiast who works with and troubleshoots a wide range of computing devices.

The phonograph record is a product of analog signal processing

The phonograph record is a product of analog signal processing

Signal Processing

Computer signal processing can be achieved through analog, digital, and hybrid forms. A signal is converted into electric pulse, radio wave, or light by a process known as modulation.

While the concept of signal processing can be as simple as an on and off direct current, it is also as complex as an alternating or electromagnetic current.

The core function of a computer is to process raw data into information, a task which is done by the microprocessor. In order for this to happen, data has to travel through some form of a pathway. This pathway is called a signal.

Computers use analog and digital signals in order to process raw data into useful information. Whereas the former is fast at processing results, the latter gives the most accurate information. Somewhere in between is hybrid processing, which is meant to combine the advantages of the aforementioned technologies.

The early systems and contraptions made at the beginning of the 20th century were analog; those manufactured at the close of the 20th century through to the 21st century have largely been digital.

Analog signals have since been superseded by digital innovations.

The transition was made possible because of the need to accomplish tasks faster and more efficiently with less clutter.

The communication industry is one area where technology had to evolve fast. While analog telephony was simple to use in the past, it was hampered because of price and limited scalability.

Digital telephony, however, has provided cheaper call rates, better call transmission quality, and improved scalability.

1. Analog Signal Processing

Humans perceive the world in analog form, which explains why everything we see, speak, and hear is transmitted in a continuous and infinite stream of information. In a sense, the human brain is a kind of a very powerful supercomputer.

Analog computers are used to model mechanical, electrical, and hydraulic quantities of nature to simulate problems or models to be solved. A running computation process is an end in itself.

Using the analog clock as an example, the minute and hour dials are constantly on the move, to tell time. We can visually measure time gone by or time to come without having to cycle between digits 0 to 9 as is in digital clocks.

Unlike contemporary computers which can be used for general purposes assignments at home and in the office, analog devices were/are used for specific industrial assignments to measure parameters that vary continuously.

They were and can be used to manipulate the following physical quantities:

  • voltage
  • temperature
  • pressure
  • distance
  • acceleration
  • velocity
  • simulation
  • force
MiniAC Analog computer was used by University of Florida for model simulation

MiniAC Analog computer was used by University of Florida for model simulation


Analog computers are solution oriented towards differential equations, where time is the most important variable. Since they produce only continuous signals, the outputs do not use word length as criteria for the ultimate computation. Usually, computation and output happen simultaneously.

The first major analog signaling computers were used to model and test various kinds of aircraft, ICBM (Intercontinental ballistic missiles), and in numerous industrial installations. Scientists in the early years turned to these systems to bring their ideas to life.

For example, in trying to perfect the suspension system in a car design, the systems could be used to simulate and thereby provide engineers better designs of pressure resistant suspensions.

As long as experimental environments could be explained by mathematical formulae, they also could be simulated using analog contraptions.

Tasks were simulated in the real world by running specified formulas and output could be read in electric voltages and various kinds of mechanical motions.

Traditional computers did not necessarily need storage resources as output because computations could be read and used real-time.

In the analog era measurement of electric current was done by use of Ammeters

In the analog era measurement of electric current was done by use of Ammeters

Examples of Analog Devices and Computers

  • Slide rule
  • Speedometer
  • Tide Predictor
  • Thermometer
  • Analog clock
  • Nomogram: a graphical calculating device
  • Operational amplifier
  • Mechanical Integrator
  • Electric integrators that solve partial differential equations
  • Norden bombsight
  • Oscilloscope: used to measure electronic instrument voltage against time.
  • Voltmeter
  • MONIAC (Monetary National Income Analogue Computer): built in New Zealand in 1949 to model UK national economic process.
  • Water Integrator Computer: Built in Russia in 1936 to solve differential equations
Analog speedometers

Analog speedometers

Analog Oscilloscope

Analog Oscilloscope

The Fate of Analog Computers

Analog computers have disappeared from mainstream establishments and can only be found in select research universities and industrial facilities, and as experimental models for computer hobbyists.

Electronic enthusiasts still fiddle around with modeling challenges of electronics because they measure real-time data to information as opposed to algorithmic data processing in modern systems.

They are also remembered as experimental contraptions and were far from achieving what digital systems have achieved by far. Despite championing parallel processing in better ways, they lagged behind when it came to usability for ordinary users.

On the contrary, digital devices have proved easy to use and the resultant data easy to manipulate and store.

In no way does this mean that analog devices and memorabilia are forever gone. It is obvious they played an important role until there arose better computation methodology and craze over personal computers.

2. Digital Signal Processing

As the words suggest, data representation is done by use of binary digits which are represented in numerals and non-numeric letters and symbols.

Unlike analog computers which measure data to information in an infinite form, digital signal processing operates by estimating data input and output using the 0 and 1 binary mode, or discrete ON and OFF electric transmission.

Digital computers are capable of delivering more accurate data because they manipulate logical and arithmetic operations like multiplication, addition, subtraction and division.

In the layman’s language, a digital system is designed to process arithmetic or logical calculations automatically using binary digits in two major states: 0 (zero) and 1 (one).

Other advantages include versatility and accuracy, and that they are easily re-programmable. Also, most information today is stored digitally in and out of the computer.

Analog to digital converters (ADC) are also used to transfer audiovisual analog recordings into the computer for purposes of storage and editing.

Laptops use digital signal processing

Laptops use digital signal processing

Differences Between Analog and Digital Signal Processing

The major difference between digital and analog computers is the manner in which they handle data. While digital computers use binary language in order to accurately effect computation, analog computers handle continuous data such as voltage changes and temperature fluctuations to output computation.



Work on continuous values

Work on discreet values


Measure quantities like speed and temperature

Solve mathematical problems like addition and subtraction


Preferable in engineering and scientific fields

Used by all and in all sectors of society


Special purpose computers

PCs are general purpose computers


May have no memory

Must have memory in order to operate


Use carefully written lists of instructions

Can connect different sub-systems together electrically with patch cables


Produce numbers as output

Output voltage signals, and has sets of analog meters and oscilloscopes to display the voltages


Vary in size from tiny contraptions, desktop size to multi rack equipment

Vary from tiny embedded systems to room-sized server systems


Storage is difficult because they use continuous signals

Numeric and discrete nature makes data storage simple

3. Hybrid Signal Processing

This is a combination of favored features in analog and digital signal processing. A hybrid system is capable of inputting analog data and outputting digital information, or vice-versa.

From a perspective point of view, hybrid computers have both the speed of analog systems and the accuracy and memory of digital gadgets.

For example, an analog device could be used to measure patient blood pressure and temperature in a medical facility and derived data is converted into meaningful digital data.

Most of the time, hybrids are designed for specialized assignments in sensitive military installations and important buildings to monitor special activities and radar functionalities.

This should be the computer of choice if the user has to process both continuous and discrete data.

Fields where hybrid computers can be used:

  • To provide cardiac catheterization data in hospitals
  • Measurement of, heartbeat, blood pressure and temperature
  • In petrol pumps

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.

© 2015 Alfred Amuno


babiti on May 11, 2019:

could you sent me , the list of an egxample of hybrid computers used in hospital

Victor on March 24, 2019:

Do analog computers use prcessor?

laxman khadka on March 17, 2018:

which one of the following is hybrid computer.....1-laptop. 2 main frame. 3. micro . 4 ECG machine.

Sabahat Malik on October 16, 2016:

It has provided me comfort to prepare my assignment ❤

Alfred Amuno (author) from Kampala on May 23, 2015:

Thanks Luis for your insight into the big intrigue of computing. I agree with you much of technology yesterday is probably going to the archives – or maybe not!

A case in point, in regards to the latter, is the evolution of measurement sensors in modern computing devices i.e. the iPhone and related accessories.

The M7/M8 coprocessor and other hardware concepts in newer iPhones should probably enlighten and lead us into understanding what the metrics hardware therein can actually accomplish.

For example, the iPhone includes barometer, gyroscope and accelerometer for fitness reasons, all which follow the old school analog approach of measuring things!

The new sensors in iPhones can track (read measure) movement related activities like atmospheric pressure, acceleration and state of inertia, and whose data can be converted to digital forms.

iPhone sensors aside, Nike, Mio, Lapka and other manufacturers have come up with all kinds of fitness accessories/contraptions that will make your smarphone accomplish much more ‘analog’ simulations than your desktop computer will ever be able to do!

Of course, the iPhone is no analog computer, but still a digital computer which can accomplish everything else your desktop computer can.

Finally, the old analog approach to measurement was based on specialized functionality and you would be tempted to question the contribution of individual devices to computation as a whole.

But again, any personal computer, or even a watch ‘device’ is a computing device in its own capacity, because it actually inputs, processes and outputs data for the betterment of the user.

Luis from San Diego on May 23, 2015:

Good point. Technology in general has gone unnoticed. What category would you say Iphones go under? Digital, analog or a hybrid computer? They obviously can't be computers because if they were you can place folders inside folders to better organize apps. An example is contacts. I would place text messages and phone in contacts. An extra folder is needed inside to separate Facebook and others because it's a different type of contacting. Notes have there own folder because you can place an unlimited amount of topics inside a central topic. do you see my point? I'm sure that computers have a combination of analog and digital technology, but don't take my word for it; do your own research. A hybrid is a combination of two strains. So would the hybrid computer be a combination of a digital and an analog computer? By the way, what's with the watch? I see no resemblance to your topic of choice. Maybe if you posted something about the mechanics and power source of the watch. Does the battery brand matter? Is the watch using less battery power because of the mechanics? Type of battery, is it a factor? What's the difference between the batteries in a watch and a flashlight? Keep your head up.