Types or Categories or Classifications of Computers

  • Classifications of Computers can be done essentially using two different types of computer processing technology. Each is made possible by a different kind of circuitry, and each is suitable for different purposes.
  • Computers are broadly classified into three major categories, based on the technology used in this computer –

(X) Analog Computers (Y) Digital Computers (Z) Hybrid Computers 

(X) Analog Computers

  • The name analog comes from the word ‘analogous’, meaning similar.
  • Analog computers are a type of computing device that processes data in a continuous, real-world format.
  • They work on/using analog data or signals (An Analog signal is a continuous signal whose amplitude can take any value in a continuous range. It can have an infinite number of values.)
  • They are generally special-purpose types of computers and are made for special works.
  • It is a machine that works through a measuring process.
  • Analog computers deal with physical quantities(such as Length, Weight, Mass, Speed, Velocity, temperature, Pressure, Volume, Force, Electricity, Time, etc.)that are continuously variable and are used to represent and process data. In other words, in analog computing, variables are represented by continuously variable physical quantities.
  • They give only approximate results.
  • Analog computers typically do not have a memory in the same sense as digital computers. They continuously process data based on the input signals they receive.
  • Analog computers are well-suited for real-time processing of physical phenomena because they operate on continuously changing input data. This makes them suitable for tasks like simulations and control systems.
  • Analog computers are particularly effective in solving differential equations, which describe rates of change in physical systems.
  • Analog computers often perform computations in parallel, with multiple interconnected components working simultaneously. This allows for the efficient simulation of complex systems.
  • It is especially useful for solving problems that involve relationships between variable quantities in systems that change with time.
  • The analog computer may express changing relationships in output in the form of graphs.
  • It is especially useful for solving problems that involve relationships between variable quantities in systems that change with time.
  • Analog computers have historically been used in various applications, including scientific simulations, engineering design, weather prediction, and control systems.
  • Examples are an analog thermometer, analog speedometer, analog watch, manual balance, etc.

(Y) Digital Computers

  • It is a machine that specializes in counting.
  • A digital computer is an electronic device that receives data, performs arithmetic and
     logical operations, and produces results according to a predetermined program.
  • It receives data through an input device (usually a keyboard) and displays the results to some output device (usually a monitor).
  • All data processing in a digital computer is done by a central processing unit, also known as a processor.
  • A working memory is used to store data and instructions in a digital computer.
  • It operates by counting values that are discrete, or separate and distinct, unlike the continuous quantities that can be measured by the analog computer.
  • The digital signal is a discrete-time signal that has a discrete number of levels.
  • It can only assume one of the two discrete values 0 or 1.
  • While analog technology uses continuous signals, digital technology encodes the information into discrete signal states.
  • Digital Computers are used for both business data processing and accuracy.
  • The basic operation performed by a digital computer is addition.
  • It can store the sums of addition problems as they accumulate and can complete a single calculation in a fraction of a nanosecond.
  • The digital computer is capable of storing data as long as needed, performing logical operations, editing input data, and printing out the results of its processing at high speed.
  • Advantages of digital systems include flexible processing, ease of design, accuracy and precision, simple operation, easy data storage, less prone to noise, etc.
  • Digital computers are electronic devices that operate on two-valued logic (On and OFF).
  • The ability of a transistor to act as a switch is the key to designing digital computers.
  • The digital circuits used in digital computers are bi-stable, with one state each corresponding to ON and OFF values. The two-valued Boolean logic (using two distinct symbols 0 and 1) serves as an appropriate representation of the states of digital circuits. Every instruction and data item therefore needs to be represented only by using two symbols 0 and 1.
  • A digital machine is capable of executing 400-500 distinct instructions and a unique binary code is required to specify every instruction, the machine instructions are specified using multiple bits (binary digits). Similarly, the data items also need to be specified using 0 and 1 only. Numbers, alphabets, and other characters can be represented by using some binary code system.
  • Data Processing Capacity :
    • The term “capacity of a computer” refers to the volume of work or the data processing capacity a computer can perform.
    • The performance of a computer is judged by the: –
      • Amount of data that can be stored in memory.
      • Speed of internal operation of the computer.
      • Number and type of peripheral devices
      • Amount and type of software available for use with the computer
    • The capacity of early-generation computers was determined by their physical size- the larger the size, the greater the volume.
  • It is a digital computer system under the control of a stored program that uses a microprocessor, programmable read-only memory (ROM), and random-access memory (RAM).
  • The ROM defines the instructions to be executed by the computer while RAM is the functional equivalent of computer memory.

Classification of Digital Computers

  • As we know computers are available in different sizes, shapes, and weights. Due to these different sizes and shapes, they perform different sorts of jobs from one another. They can be classified in different ways.
  • All the computers are designed by qualified computer architects who design these machines as per different requirements.
  • Computers are classified into various categories in different ways –

(A) On the basis of its development/evolution, they are of the following types – 

(a) First Generation Computer (b) Second Generation Computer (c) Third Generation Computer (d) Fourth Generation Computer (e) Fifth Generation Computer 

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(B) On the basis of the purpose/use of computers in various applications, computers are of the following types –

(a) General Purpose Computer (b) Special Purpose/Dedicated Computer

(a) General Purpose Computer

    • When a computer is designed for doing/able to perform a variety of computing tasks, is called a general-purpose computer.
    • They are normally able to accept different applications.
    • Most computers in use today are General-Purpose computers.
    • A general-purpose computer is able to perform a wide variety of operations because it can store and execute different programs in its internal storage.
    • Simply by using a general-purpose computer and different software, various tasks can be accomplished, including writing and editing (word processing), manipulating facts in a database, tracking manufacturing inventory, making scientific calculations, or even controlling an organization’s security system, electricity consumption, some business works, etc.
    • Examples – Most digital computers are of this nature i.e. All mainframes, servers, laptops, and desktop computers, as well as smartphones and tablets are general-purpose devices.
    • ENIAC was the first general-purpose computer.     

(b) Special Purpose Computer

    • A special-purpose computer is designed to be task-specific and most of the time its job is to solve one particular problem.
    • They are also known as dedicated computers because they are dedicated to performing a single/specific task over and over again.
    • Special-purpose computers are generally designed to solve problems repeatedly in accordance with previously prepared programs while periodic or continuous changes occur in the input data. 
    • The most common examples of special-purpose computers are pipeline processor architectures for graphics, with at least 3 companies (AMD, Nvidia, Intel) producing graphics processors that they call GPUs specifically for computer graphics.
    • Examples – Most of the analog and some digital computers are of this nature.
    • Such a computer system would be useful in playing graphic intensive Video Games, traffic light control systems, navigational systems in aircraft, weather forecasting, satellite launch/tracking, oil exploration, automotive industries, keeping time in a digital watch, or Robot helicopters, etc.
    • As these computers have to perform only one task, therefore, they are fast in processing. 
    • These computers lack versatility and hence cannot be used to perform other operations.      

(C) Computers are available in different sizes, shapes, and weights. Due to these different sizes and shapes, they perform different sorts of jobs from one another. On the basis of different sizes, shapes, and weights computers are of the following types –

(a) Micro Computer (b) Mini Computer (c) Mainframe Computer (d) Super Computer

(a) Micro Computer

      • They are small size computers.
      • Today microcomputers are also popularly called Personal Computers and are more accurately called IBM PCs and Apple Macintosh.
      • Intel’s founder, Robert Noyce, chartered Ted Hoff’s Applications Research Department in 1969 to find new applications for silicon technology -the microcomputer was the result.
      • Since microcomputers were originally designed for personal use they are also referred to as personal computers or PCs. Due to the advancement in hardware technology, powerful PCs have been developed since the 1980s.
      • The essential characteristics of these microcomputers are: –
        • Small size and low cost.
        • Single-user computer.
        • Easy to use.
        • Comparatively low computing power but sufficient.
        • Commonly used for personal application.
      • The microcomputers contain single processors/microprocessors that literally contain a complete processor on a single chip.
      • Microcomputer memories are generally made of semiconductors fabricated on silicon‟s chips.
      • It is a digital computer system under the control of a stored program that uses a microprocessor, programmable read-only memory (ROM), and random-access memory (RAM).
      • The ROM defines the instructions to be executed by the computer while RAM is the functional equivalent of computer memory.
      • These are small, relatively inexpensive computers designed for personal use in homes, offices, and small businesses.
Examples of Micro/Personal Computers : 

(i) Workstations :

        • A workstation is a high-performance microcomputer that is used for scientific and technical tasks such as computer graphics, scientific simulation, computer-aided design (CAD), image processing, engineering calculations, etc.
        • It is generally used in such applications which require a moderate amount of computing power. Hence, the configuration of the workstation used to be high.
        • UNIX and Windows NT are the most common Operating Systems for workstations.
        • Workstations are generally single-user systems however they can be connected together to form a LAN.
        • In the context of networking, workstations are sometimes referred to as any computer/terminal attached to a LAN.
        • In a networked workstation, the system administrator tracks and controls the activities of the user.
        • The term workstation is also used for high-capacity mainframe computer terminal or a PC connected to a network and working in client-server mode.
        • A workstation has superior processing and storage capabilities than a normal PC, especially with respect to providing multitasking capability.

(ii) Personal Computer (PC) :

        • A personal computer (PC) is a general-purpose computer, used for day-to-day activities in different areas including education, business, administration, and health.
        • Due to its size and capabilities, the PC is useful for users.
        • A PC can be operated directly and may be used for computational, word processing, and data storage purposes.
        • Depending on the size and processing capacity, PCs are of many types such as a desktop computer, a laptop, a tablet PC, or a handheld PC /palmtop.
        • Personal computers can be connected to the computer network by wired or wireless media.
        • PCs are being used by school-going children to business professionals for different purposes. A non-professional user may use a PC to listen to songs, watch movies, create some documentation, email, etc. A professional user may use a PC for different business processes such as documentation, running business programs, creating databases, internet, emailing, teleconferencing, etc. Thus, the scope of a personal computer varies a lot depending on the type of its users.
        • The configuration of a PC matters a lot in terms of its processing quality and cost.
        • The most common PCs are – 

    (a) Desktop Computers :

          • A desktop computer is popularly known as a personal computer (PC).
          • As the name suggests, it is generally small in size and fitted on the top of a desk which can be used at a fixed location.
          • Most modern desktop computer has separate monitor screens and keyboards.
          • Generally in the majority of the PCs, Microsoft Windows, LINUX, and Mac OS are used as operating systems.
          • Desktop computers are available in many different forms from large vertical tower cases to small form factor models.
          • The advantages of desktop computers are that they may be used for day-to-day computational and internet communication activities in offices, schools, etc.
          • A PC provides more space for heat to escape. Also, the power consumption of a PC is not very high.
          • There are many brands of PCs available in the Indian market and abroad including HP, HCL, Wipro, Compaq etc.
          • A PC also can be assembled as per specific requirements, instead of a particular brand.

    (b) Laptop Computers :

          • A laptop is also a personal computer but intended for use in a single place.
          • It is small in size, portable, and can be used anywhere.
          • Portability is one of the main advantages of a Laptop over a tablet PC.
          • Another advantage of a Laptop is that it contains batteries which are used for power supply. It makes a laptop usable even if power is not available.
          • In a laptop, almost all the components are attached as a single unit. Although some devices like mice, can be attached externally through ports.
          • The basic components of a laptop are similar in function to the desktop computers.
          • Most modern desktop computer has separate screens and keyboards.
          • Generally in the majority of the PCs, Microsoft Windows, LINUX, and Mac OS are used as operating systems.
          • Laptops are much more power efficient than desktops.
          • The major disadvantage of Laptops is that their upgradeability is limited as compared to desktops.
          • There are many brands of laptops available in the Indian market and abroad including HP, HCL, Wipro, Compaq, Dell, Lenovo, Toshiba, Sony, etc.

    (c) Notebook Computers :

          • Netbooks are a special type of Laptop which is very light and small.
          • Due to its size and weight, it is very portable and one may carry it very easily.
          • Dissimilar to Laptop, it does not require a separate carry bag for it.
          • Netbooks are suitable for general-purpose computing works and for accessing the Internet.
          • They also use less powerful hardware than most laptops.
          • Due to limited processing capabilities, Netbooks are less expensive than laptops.
          • Due to its size and portability Netbooks are becoming very popular for education and business works.
          • Works related to word processing, presentation, internet access, multimedia, etc can be easily carried out on a Netbook.
          • Generally in Netbooks, Windows, Linux, and Android operating systems are used along with others.
          • There are many brands of Netbook available in the Indian market and abroad including Acer, HP, Dell, HCL, Apple, Sony, etc.

    (d) Tablet PC :

          • A tablet PC is similar to a personal computer.
          • It is a portable device that has a touch screen for inputting the data.
          • A tablet computer can connect to the internet and local computer network through wireless.
          • In general terms, a tablet PC refers to a slate-shaped mobile computer device, equipped with a global positioning system (GPS) System, and a touch screen to operate the computer.
          • It is generally equipped with office suits such as Word, excel, etc, web browsers, computer games, and other similar applications, that generally can be run on a PC.
          • Tablet PCs can also use handwriting recognition and virtual keyboards for input of data.
          • In, tablet PCs Microsoft Windows, Linux, and Apple operating systems are used.
          • There are many brands of Tablet PCs available in the Indian market and abroad including Acer, Lenovo, Panasonic, Toshiba etc.

    (e) Smartphones :

            • A smartphone is a mobile communication device that combines the functionality of a traditional cell phone with features and capabilities commonly associated with personal computers.
            • Smartphones have become an integral part of modern life, providing a wide range of functionality and convenience in a portable and compact form. They are used for communication, productivity, entertainment, and much more, making them one of the most ubiquitous and versatile consumer electronics devices.
            • Smartphones allow users to make and receive calls and send text messages. Many also support video calls and a variety of messaging apps.
            • Smartphones can run a vast array of applications (apps) that are available for download from app stores. These apps can cover a wide range of functions, from productivity tools to games and entertainment.
            • Most smartphones feature a touchscreen interface, which enables users to interact with the device by tapping, swiping, and gesturing on the screen.
            • Smartphones are highly versatile and can perform a wide range of tasks beyond voice communication, such as internet browsing, email, multimedia playback, photography, video recording, gaming, and much more.
            • GPS capabilities enable smartphones to provide navigation services, mapping, and location-based information.
            • Smartphones come equipped with various sensors, such as accelerometers, gyroscopes, ambient light sensors, and more, which enable features like automatic screen rotation, fitness tracking, and augmented reality applications.

    (f) Personal Digital Assistance(PDA) :                   

            • Personal Digital Assistance, often referred to as a Personal Digital Assistant (PDA), is a term that has evolved over time and can refer to a range of technologies and tools designed to assist individuals in various aspects of their personal and professional lives.
            • personal digital assistance encompasses a wide range of tools and technologies that aim to help individuals manage their personal and professional lives more effectively.
            • From early standalone PDAs to the integration of AI and voice assistants into smartphones and other devices, these tools have become an essential part of modern life, offering convenience and efficiency in various aspects of daily living.
            • The concept of PDAs has undergone significant changes as technology has advanced. Here are some of the main phases in the evolution of personal digital assistance:
              1. Early PDAs: 

                • In the 1990s and early 2000s, PDAs were standalone devices designed primarily for organizing personal information.
                • The Palm Pilot and early Pocket PCs are examples of such devices.
                • They featured touch screens, stylus input, and basic applications for tasks like managing contacts, calendars, and to-do lists.
              2. Smartphone Integration:

                • With the rise of smartphones, the concept of personal digital assistance evolved. Modern smartphones, like those running iOS and Android, incorporate features and apps that effectively serve as PDAs.
                • They offer not only basic organization tools but also internet access, email, GPS, and a wide range of apps for various tasks.
                • Voice Assistants: Voice-activated personal digital assistants like Siri (Apple), Google Assistant (Google), and Alexa (Amazon) have become integral parts of many people’s lives. They allow users to interact with their devices using natural language and provide assistance in tasks like setting reminders, answering questions, controlling smart home devices, and more.
              3. Artificial Intelligence and Machine Learning:

                • The integration of artificial intelligence (AI) and machine learning into personal digital assistance has significantly enhanced their capabilities. These technologies enable personalized recommendations, predictive assistance, and the ability to learn from a user’s behavior to offer more relevant support.

              4. Wearable Devices:

                • Smartwatches and other wearable devices often include PDA functionality. They can display notifications, track fitness, and health metrics, and provide quick access to personal information and apps.

              5. Virtual Assistants for Business:

                • In a professional context, personal digital assistance can also refer to tools like virtual assistants or AI-powered software designed to streamline tasks, such as scheduling, email management, and data analysis. These tools are used to boost productivity in the workplace.

              6. Personalization and Privacy:

                • As PDAs become more integrated into our lives, concerns about data privacy and security have grown. Users need to be mindful of the data they share with these systems and understand how it’s used.

    (b) Mini Computer

        • Mini computers, also known as minicomputers or midrange computers, are a class of computers that are smaller and less powerful than mainframes but more capable than microcomputers (personal computers).
        • Minis are often used for tasks that require moderate computing power and are commonly found in scientific, industrial, and business applications.
        • Minicomputers are typically more affordable and easier to maintain than mainframes, making them suitable for a variety of applications where moderate computational power is required without the expense and complexity of mainframe systems.
        • Mini computers are near to medium size computers.
        • Medium-size Computers :
          • It provides faster operating speeds and larger storage capabilities than small computer systems.
          • These Computers can support a large number of high-speed input-output devices, and several disk drives can be used to provide online access processing.
          • The possibility of increasing the data processing capability of a computer by adding devices, such as additional memory, and other peripheral devices, is called expandability.
          • Although the minicomputer is not as powerful as the medium or large-size computer, it is quite close.
        • Minicomputer systems (also called small mainframe computers) provide faster operating speeds and larger storage capacities than microcomputer systems.
        • These Computers can support a large number of high-speed input/output devices.
        • Several desk drives can be used to provide online access to large data files as required for direct-access processing.
        • Operating systems developed for minicomputer systems generally support both multi-programming and virtual storage i.e. many programs can be run concurrently.
        • This type of computer system is very flexible and can be improvised to meet the needs of users. 
        • Several desk drives can be used to provide online access to large data files as required for direct-access processing.
        • The minicomputer is not as powerful as the medium or large-size computer, rather it is quite close.
        • Examples are – Data General Nova,  PDP-11 and PDP-8, DEC’s VAX series mini, IBM’s AS/400, Hewlett Packard’s HP 3000 series, Sun-3 series, NCR Tower series mini

    (c) Mainframe Computer

        • Mainframe computers are near to large size computers.
        • Mainframe computers are powerful and high-performance computing systems used for large-scale, critical, and resource-intensive tasks. They are typically employed by large organizations, such as government agencies, financial institutions, and major corporations, to handle complex data processing, transactional processing, and other mission-critical operations.
        • Mainframes are chosen for their reliability, scalability, and ability to handle massive workloads.
        • Mainframes are commonly used in environments where data security, uninterrupted operation, and processing speed are critical, such as banking, healthcare, airline reservations, and large-scale transaction processing.
        • Large Size Computers : 
          • These Computers are the ultimate in flexibility and speed.
          • These usually contain full control systems with minimal operator intervention.
          • Large computer systems range from single-processing configurations to nationwide computer-based networks involving general large computers.
          • Large computers have internal operating speeds measured in terms of nanoseconds, as compared to smaller computers where speed in terms of microseconds.
        • Mainframe computers are huge, multi-user systems designed to process millions of instructions per second and capable of accessing billions of data.
        • They can handle gigantic processing jobs in large corporations or government agencies.
        • This computer is commonly used in big hospitals, airline reservations companies, and many other huge companies that prefer mainframe because of its capability of retrieving data on a huge basis.
        • Mainframe allows its user to maintain large information storage at a centralized location and be able to access and process this data from different computers located at different locations.
        • Mainframe computers are normally too expensive and out of reach for a salaried person who wants this computer for his home.
        • The mainframe is the second largest in capability and size of the computer family.
        • Examples are – IBM Z Series mainframes, Unisys mainframes, Fujitsu’s GS21 series, HPE’s NonStop Systems, etc.

    (d) Super Computer

        • They are near to the largest size computer.
        • The most expensive in price, biggest, and fastest machines today are the supercomputers that are used when billions or even trillions of calculations are needed.
        • Supercomputers are ultra-fast computers designed to process huge amounts of scientific data and then display the underlying patterns that have been discovered.
        • These machines are essential for applications ranging from nuclear weapons to accurate weather forecasting.
        • The Super Computers are used for highly calculation-intensive tasks such as molecular modeling, climate research, weather forecasting, quantum physics, physical simulations, etc.
        • Supercomputers are machines that have speed in the 100-million-instructions-per-second range.
        • Governments especially use this type of computer for their different calculations and heavy duty.
        • Different industries also use this huge computer for designing their products.
        • It is also used for animation purposes.
        • The CDC 6600, released in 1964, is sometimes considered the first supercomputer.
        • The PARAM supercomputer is one of the supercomputers developed by India‟s Center for Development of Advanced Computing(C-DAC) and promises processing speeds of up to 1 trillion instructions per second.
        • Since October 2010, the Tianhe-1A supercomputer has been considered the fastest supercomputer in the world which is located in China.
        • Some examples of supercomputers are – IBM Blue Gene/L, IBM Roadrunner, Cray Jaguar, etc.
        • PARAM Siddhi-AI, Pratyush, and Mihir are some of the names of supercomputers in India,


    (Z) Hybrid Computers 

    • A computer that combines the best features of both types of computer i.e. analog and digital computer. Here, Analog computers process continuous data, such as electrical voltages, to perform operations like differential equations and simulations. Digital computers, on the other hand, work with discrete data represented in binary form, making them suitable for a wide range of numerical computations.
    • They are designed to leverage the strengths of analog and digital computing to solve a wide range of complex problems.
    • One of the primary advantages of hybrid computers is their ability to process real-time data.
    • This is a special-purpose machine called a hybrid computer which combines the measuring capabilities of the analog computer and the logical and control capabilities of the digital computer.
    • It offers an efficient and economical method of working out special types of problems in science and various areas of engineering.
    • Some Hybrid machines contain special equipment to convert analog voltages into digital voltages, and vice-versa.
    • Hybrid computers have been employed in various fields, including aerospace, automotive engineering, nuclear physics, weather forecasting, and scientific research. They are particularly useful for tasks that require precise modeling of complex physical systems, such as flight simulations and automotive crash testing.
    • Designing and maintaining hybrid computer systems can be complex and costly due to the need for both analog and digital expertise.



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