CET1171 Lecture #1 - Definition of a Computer

Materials:
Lecture Only
Objectives:
The student will know what a computer is,
Where the term came from,
What it means and
What the modern digital computer does.
Competency:
The student will become familiar with the core concept of the term computer including its origin and meaning including the basic functionality of the modern digital computer.

Procedures

  1. The term computer was used extensively by the mathematician Alan Turing in his body of work that was done in the !930's. Turing developed many theorems concerning the definition and nature of computing as a purely abstract mathematical concept and his works form the foundations of modern computational theory taught worldwide under the heading of Computer Science.

  2. Turing used the term very generically refering to anything that could compute; that is, anything that could be given a problem such as "2 + 2" and that could generate the result "4" as long as we realize that the same "computer" should be equally capable of generating the answer to any addition problem of the form "a + b" Therefore, Turing's computers in the 1930's were mechanical adding machines, and human beings.

  3. In his mathematical treatises Turing used a generic computing machine that has come to be known as the Turing Machine. The significance of the Turing machine is that he used it to develop theories concerning the "computability" of a given class of problems like the class "a + b" mentioned above. Turing was able to prove mathematically that there are special cases of computable classes of problems that are non-computable; that is, a computer cannot find the answer. He also showed that there exist whole classes of uncomputable problems. These theories are the cornerstone of modern computer science. Using the Turing theories it may be possible to identify a given problem as being a member of a class of problems that is non-computable and therefore a waste of time to give to the computer since a program cannot be created that will solve it. You are familiar with a very well known non-computable problem that you encountered in grade school of the form: x ÷ 0 = ? which of course cannot be solved. Turing's theories can be used to take a very complex problem and break it down to demonstrate whether it is definitely computable, definitely non-computable or undeterminate as to whether it is computable. This is at least a head start for the programmer.

  4. So a computer can derive an answer to a problem, but the most general definition of a computer is something that can be given a raw set of data: the "2" the other "2" and the desire to add them, and then process this input and generate the output of the "4". To this end the general definition of the computer is:

      Definition: Computer: Input (raw data) => Process => Output (information)
    
  5. This works perfectly fine for adding machines, calculators, computers embedded in modern automobiles, ATM banking machines, IBM mainframe computers, desktop PC's and even humans. However, the modern definition of the computer is not really complete without defining it fully like this:

  6. As this illustration suggests, the modern computer can also store the raw input, any stage of the process and the output so that the computation can be continued or repeated at a later time. In general, the modern definition has been refined as:

      Definition: 
      (Modern) Computer: Input => Process => Storage => Output 
    
  7. This information storage capability is such an important part of the modern definition of an electronic computer that some computers are completely devoted to doing nothing more than store data and information for retrieval and do little else, this being their primary function. And most modern general purpose digital electronic computers would be virtually useless without the ability to store data and information including their own operating systems so that they can start up and reach a point where they can execute a program that will accept the input data, process it and output the information at all.

  8. So now that we know what a computer is, and that this definition does encompass everything from adding machines to calculators to ATMs to supercomputers to PC's then the computer obviously has categories. For now we will pursue the realm of digital electronic computers as opposed to mechanical computers like adding machines or living computers like people. The two main categories or families of digital electronic computers are the special purpose computer and the general purpose computer.

  9. Special computers are designed often at the circuitry level to perform one specific class of tasks. Because they are designed specifically to perform this task they are usually extremely good at it and suffer few if any flaws and are also very fast. Because the circuits have been designed to perform the tasks required of this type of computer they are generally unable to be reprogrammed to perform any other task; hence the term "special purpose computer." They can only perform the special purpose for which they were built. A good example of a special purpose computer is the calculator, car engine controller, and a digital clock.


    Typical calculator, a special purpose computer

  10. General purpose computers on the other hand can be reprogrammed to perform any task that a computing machine can perform. In fact, general purpose computers are usually designed specifically around this functionality: to allow a programmer to load any program desired first and then execute it. Thus, a general purpose computer is nothing at all until it loads a program which provides the machine with the set of instructions needed so that it can perform some computing task. A general purpose computer is also designed so that it can then quit the loaded program, load another one and begin this other computing task. So while running the calculator program the computer will be a calculator and be able to accept numbers and add, subtract, multiply, and divide them. When the calculator program is ended and the word processor program is started the computer is now a word processor with all of the capabilities of being a paperless typewriter that can perform spell checks, change fonts, embed images and tables, and preview on screen and then send the formatted document to the printer.

  11. So a general purpose computer is purposely nothing at all, a clean slate, into which any program can be loaded and then and only then does the computer become what the program is. In this way, whatever a computer can do, a general purpose computer can do if the program is written and available for the machine to execute it. This is exactly why the software for a general purpose computer is so valuable, because the general purpose computer will do nothing until the software is loaded into it and executed.

  12. At this point the types of general purpose computer will be discussed and these types have to do really with each one's size and computing capacity because they are all general purpose computers capable of begin programmed to do anything that a computer can do. The types are:

    Supercomputer
    Mainframe Computer
    Minicomputer
    Microcomputer

  13. The supercomputer is basically the largest and most powerful computer at the time it is built. Like any piece of hardware it gets frozen in time and as it ages, newer technologies are developed and then newer machines become the most powerful computers, so supercomputers have the problem that they will become obsolete rather quickly especially as time goes on technology itself is growing at an exponential rate meaning that computers are getting faster and faster at a faster and faster rate! Supercomputers are not assembly line manufactured. They are special ordered and they are very expensive; only governments and very large corporations can afford them. Because they are large they can be called "installation level" computers that are so big and expensive that it is very impractical to move them once set up and they usually occupy their own section of a building or even an entire building dedicated to keeping the machine in a stable environment with low temperature, humidity, and dust. Supercomputer installations usually have a separate electrical power supply to be sure they never accidentally lose power while running. Supercomputers are usually measured in tflops - tera-floating point operations per second in which the "tera" means trillions. So a particular supercomputer that is said to be a "8.9 tflop" computer can perform 8.9 trillion floating point mathematical operations on numbers per second. A good example of a supercomputer customer would be the National Oceanic and Atmospheric Administration who might order a new supercomputer for attempting to run simulations based on huge bodies of temperature and pressure data going back decades in order to develop hurricane track predictions.


    IBM Supercomputer located in Jülich Germany

  14. A mainframe computer is another very expensive computer that is the largest production computer available at the time. These are very powerful machines that usually employ recent supercomputer technologies so there is only a small lag in computing power. In fact because they are quite modular in design, it might be possible to build up such a large mainframe that it would have the computing power of a supercomputer of the day, but it would certainly cost as much if not more. Mainframes are physically large machines costing millions of dollars and are therefore certainly "installation level" computers. They need very well environmentally controlled locations not only air conditioned, but humidity must be kept extremely low, intruders must be deterred, the possibility of fire must be minimized, and electrical power interruptions must be avoided. Mainframes are quite often installed into their own buildings with a minimum of flammable materials in the construction and a sophisticated and powerful fire control system such as a halon system that can literally hermetically seal the building and remove all oxygen from the air in seconds. Mainframes will certainly run off of off-line battery powered uninterruptable power supplies that can in turn be powered by diesel generators in the event of a total power blackout in the area.


    A typical mainframe system


    A mainframe battery backup power supply

  15. It should come as no surprise that supercomputers are just as well cared for. And it should come as no surprise that only governments and large corporations have the resources to invest in these big expensive machines. Many businesses including banks and national chain stores have mainframes. Mainframes are physically large computers that occupy large cabinet-sized modules that contain their circuit boards and peripheral devices and these can be added on to them practically without limit resulting in the need for a large floorspace and hence the concept of placing the mainframe in its own building or section of a building.

  16. The minicomputer is a scaled down version of a mainframe. It is basically a mainframe in a small box (relatively speaking.) Furthermore, it is usually a directly compatible descendent of the mainframe of the same manufacturer meaning that it really is their mainframe product adapted to fit into a small box and it can run the expansion cabinets and peripherals of the mainframe computer. Minicomputers are still quite powerful and can be expanded up to mainframe power. Large stores like Publix and WalMart could easily have a minicomputer in the store running all of the cash registers and automatically tracking sales and inventory on the fly.


    An IBM AS/400 Family minicomputer

  17. The last category is of the most interest to the home user, small office and the student technician: the microcomputer. The term microcomputer is synonymous with "personal computer" and basically means any physically small system that is easily transported and set up by an individual (as opposed to the installation level types of computers mentioned above) and which is also reasonably affordable (as opposed to the minicomputer which can be fairly compact but is certainly not affordable). These two aspects of the microcomputer in particular make it a personal computer whose strict definition is a computer intended for the population of home users as opposed to business and governments as the intended buyers.


    World's first microcomputer: the Altair 8800

  18. The microcomputer because of its small physical size and budget is necessarily compromised. In general, these computers support a single user whereas the preceding categories of computer are all capable of executing large numbers of separate tasks for large numbers of users simultaneously. Microcomputers usually have a single microprocessor, limited quantities of RAM, hard drives, and other internal and external expansion peripherals. Because of this the computing performed by these machines is done entirely by the single processor and it in fact is the computer. The motherboard to which it is attached holds the chipset which are a collection of intergrated circuit components that work to interface the microprocessor with the rest of the hardware of the computer including the keyboard, video controller, storage devices and so on. The architecture of the motherboard then is open to the engineers who design it and the architecture of it is more specific to the specific model of personal computer than the processor itself. For a given processor two completely different motherboards can be developed such that software will function on one but not the other because of the way the processor and the devices interface with each other.


    World's first "modern look and feel" personal computer: The Apple II

  19. Because of the specific nature of the motherboard architecture and the fact that the microcomputer is a specific microprocessor it can be said then that the choice of the CPU and the motherboard architecture determine the particular model of microcomputer. This is exactly the distinction between the Apple Macintosh and the IBM PC, for example. They are based on different CPU's with unique machine languages that require completely different software designed for the specific CPU. Furthermore, if the processor of the IBM PC were installed on a motherboard that were to use a totally different architecture, then the software for the IBM PC could not possibly work.


    The IBM PC

  20. The IBM PC is a specific personal computer based on the Intel 8088 processor and a specific off-the-shelf motherboard that was adapted by IBM for it. The IBM PC's components were all available over the counter when it was built and IBM could not patent, trademark, or copyright any of it. This would turn out to be a boon for the IBM PC as an industry, but in the end a total bust for IBM the corporation because they are now for all practical purposes gone from the IBM PC industry. This type of product, that the OEM - Original Equipment Manufacturer, cannot collect licensure or royalty fees if another company makes replicas of it is called open architecture. Open architecture generally leads, with successful products like the IBM PC, to strong competition which the PC industry has enjoyed since its inception until now. This strong competition for the consumers' dollars leads to improvements in the performance of the product itself which the PC has certainly seen, and improvements in price which the PC has also seen steadily from day one.

  21. The other major marketing concept involved in the IBM PC that allowed it to "win" the personal computer "war" that existed when it was introduced was backwards compatibility. As each new model of PC was introduced, IBM made sure that the newest model could still run all existing software that ran on the predecessors, and that all peripheral devices attached to the older models could also be removed from them and attached to the new model and function flawlessly. Well, most software and hardware could be moved to the new model.

  22. The accidental open architecture strategy happened because IBM was in a hurry to get a personal computer into the suddenly booming personal computer market, so they borrowed everything, Intel's microprocessor, existing motherboards, and components. Since they did not make any of the parts, they could not patent them either. They proceeded to publish the interface standards and a third party market of software and hardware manufacturers literally exploded into existence. Everyone knew that if they got into that market they would do very well; and they did indeed.

  23. The backwards compatibility ensured that the end user's hard earned dollars spent on software and hardware were never wasted, they could always move these into their new computer. And it extended the effective functional lifespan of virtually every product in the PC industry from all of the software packages which could run on PC's made years after the original release, to peripherals made years earlier.

  24. This allowed the PC to effectively eliminate all competition within two years of its introduction in 1981. This accidentally caused the IBM PC to solve the single greatest threat to personal computing at that time: the lack of universal compatibility. Apple IIe owners could not share diskettes with Atari 800 owners who could not share data files with Texas Instruments TI-99 owners who could not share game programs with Tandy TRS-80 owners. In fact nothing could be shared between different personal computer models from the same manufacturer much less between different manufacturers equipment. It was segregating the computer users into little isolated groups, rather than working to unite all of the worlds nerds. The IBM PC in the end would unite them all by default: it was the only personal computer left standing, the only one everyone was using so of course all of the disks, files and programs worked since everyone was using the same computer. That's one way to solve the universal compatibility problem! Default is a commonly used term in the computing industry and means: the standard assigned value. When any program starts for the first time, it must have some values initialized to some value, rather than nothing at all, so that the program can begin to execute. The programmers therefore preload these values with "default" settings that can be changed once the program starts. The PC is full of default settings that can later be changed.

  25. The terms hardware and software have been in heavy use here and should now be formally defined:

    Hardware: physical components and peripherals.

    Software: information, the numbers stored on and used by the hardware to perform computing tasks

  26. There are two types of digital numeric values held in and used by the computer hardware:

    Data: The raw data or the information resulting from the processes performed on the raw data.

    Code: the machine language instructions listing the steps of the processing that the computer must perform on the input raw data that results in the output information.

  27. The digital numeric values stored in and used by the computer are organized in ascending groups based on their sizes:

    bit: The contraction of the words: Binary digIT means a single digit number but in the binary number system not the decimal number system that we normally use.

    byte: an 8 Binary digIT number; the standard sized digital numeric value that is stored and used throughout the computer.

    word: a 16-bit number.

    dword - double word: a 32-bit number.

    qword - quad word: a 64-bit number.

    file: complete set of information, raw data, and/or code stored as bytes.

  28. The two basic types of files are: executable files or programs that perform one or more tasks, and data files that hold either raw input data or information, data that has had some level of processing done to it by a program. There is a third type of file called an object that contains both data and executable code wrapped into one "object" for lack of a better term.

  29. The largest organization or collection of digital numeric values described above was the file, and these complete sets of data or code are the most convenient units of computer information that users actually use. It is easier to copy a file than the first, then the second then the third bytes of data, and so on. Files however, are potentially quite large collections of data and/or code and must be organized so that they can be found again when needed by the user. The computer must therefore have a file system set up on the permanent storage devices for this purpose. Here are the computer file system's logical containers for information:

    file: a complete set of information either data and/or code.

    directory: a container for files and/or more directories.

    volume or partition: a section of a permanent storage device that can hold the root directory of a complete isolated file system within it.

Review Questions

  1. What is the basic definition of a computer?


  2. What is the definition of a modern digital electronic computer?


  3. Who is attributed with coining the term "computer" in the modern sense of the word and what did he do?


  4. What are the two main categories of the modern digital electronic computer?


  5. Give three examples of special purpose digital electronic computers. Describe special purpose computers.








  6. Describe the general purpose computer and give the four types of them.











  7. Describe the supercomputer.


  8. Describe the mainframe computer.


  9. Describe the minicomputer.


  10. What term is synonymous with the microcomputer? Describe it.





  11. What component is the computer within a microcomputer?


  12. What two items distinguish the IBM PC from any other personal computer?


  13. What two major marketing concepts helped the IBM PC become the dominant personal computer in the market within just a few years of its introduction?


  14. By becoming the only personal computer left in the market, what major problem did the IBM PC solve?


  15. Define hardware.


  16. Define software.


  17. When a device, like the IBM PC, has no licensure, trademark, or copyright restricting other manufacturers from making it, this is called:


  18. Even though the definition of a digital electronic computer is Input -> Process -> Output, some computers instead are dedicated entirely to:


  19. The first IBM PC was based on what particular microprocessor?


  20. Name another personal computer that is not the IBM PC nor is it compatible with it.


  21. Name the two features that distinguish a personal computer from the other three categories of general purpose computers.


  22. Describe the term "Installation Level Computer."


  23. Personal computers in general support how many microprocessors and limited amounts of what items?





  24. Of the four categories of general purpose computer, which is the only one never designed to support multiple users simultaneously?


  25. What one feature ensures that the minicomputer can not qualify as a personal computer?


  26. What are the two types of digital numeric values held in and used by the computer?


  27. List and define the organizations of digital numeric values held in and used by the computer in ascending order based on their size:











  28. List and define the logical containers for information used in computer file systems in ascending order based on their size:








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