Classifications of computer-BASED

There are basically three types of computers namely:-  Analogue, Digital and hybrid computers.

Analogue Computer:

A computer that performs computations [such as summations, multiplication, integration and other operations] by manipulating continuous physical variables that are analogs of the quantities being subjected to computations. The most commonly used physical variables are voltage and time. Some Analogue computers use mechanical components, the physical variables become, for example angular rotations and linear displacements. Examples of analogue computers include some wrist watches, car speedometers, thermometers etc. This computer is mainly used for research and scientific analysis. In research. The analogue computers are useful in the hospitals, Research Laboratories, Geology, Air- fields etc. In calculus, this computer are used in the solution of field problems like conductive and convective  heat transfer , fluid flow and structures. The nature of this type of problem is partial Differential Equations (PDE) and ORDINARY DIFFERENTIAL EQUATIONS (ODE). Generally, the analogue computer process data in form of electrical voltages, which are variable, like the variable positions of a pointer on a dial. The output  from analogue computers is often in the form of smooth graphs which information can be read. The analogue computers are grouped into two branches, these include:- Direct analogue computer (Special Purpose) and Indirect analogue computers (General purpose). 

Digital Computers

A computer that operates on discrete quantities. As the name implies, the digital computer is one which process data that are represented in the form of discrete values or non-continuous, such that they are either on ON or OFF ( 1 or 0 ) with no intermediate values steps.

Digital computers are also called binary because, they work with numbers in the form of separate digits. More precisely, they work with information that is digital or character form, including alphabetic and other symbols as well as numbers. They have different degrees of accuracy depending on their construction and machine characteristics. Digital computers are used mostly in business applications. For example, a computerized cash register is a digit number. It uses binary digits to precisely represent sales amount.

Hybrid Computer

A computer (system) that contains both a digital and an analogue computer features. The digital computer usually serves as the controller and provides logical operations. The analogue computer normally serves as a solver of differential equations. The hybrid computer is a combination of high- speed electronic analogue computer and a scientific digital computer linked together by a communication interface system. Hybrid computers are however, actively manufactured by several domestic and a number of foreign firms and continue to find application in the aerospace, process industries and in education.

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Auxillary and Secondary Storage Device

SECONDARY STORAGE DEVICES.

Although speed is still a very important criterion, the main objectives when dealing with secondary storage are data integrity and mass storage capability, coupled with low cost. Auxiliary, external, or backing store are alternative names for secondary storage.

Computers can save information permanently, after you turn them off. This way, you can save your work for future use, share information with others, or modify information already available. Secondary storage holds information external from the CPU. It allows you to store programs, such as Microsoft word and Micro soft Excel. It also allows you to store the data processed by programs, such as document file, text in MSWORD.

We described main memory in five. This is the internal and temporary storage of data and programs in the computer’s memory. Once the power is turned off or interrupted, everything in internal storage disappears. Such storage is therefore said to be volatile storage. Thus, we need external, more permanent or non volatile storage for data and programs. We also need external storage because users need much more capacity than is possessed by a computer’s primary memory.

Competent users need to be aware of  these secondary devices. Secondary storage devices are devices permanently hold data and information as well as programs. They include:

Floppy disk

 Hard disk

Optical disk

Magnetic disk

Flash disk

Magnetic tape

PROPERTIES OF  SECONDARY STORAGE DEVICES

1.  physical parts: Any secondary storage system involves two physical parts, a peripheral device and an input/output medium. A disk unit and tape unit are examples of peripheral devices; magnetic disk platters and magnetic tape cartridges are type of media. Data and programs are written onto and read from some type of medium. The medium must be situated on a peripheral device for the CPU to process its contents.

In most secondary storage systems, media must pass by a read/write head in the peripheral device to be read from or written to. For instance, when you play or record to a music tape on your home stereo system, the tape passes a head on the tape recorder, which will either play or record music . magnetic tapes on computer systems work by an identical principle. Magnetic disks also use read/write heads that perform similar types of reading and writing tasks.

2.  Non-volatility Property

Secondary storage media are non-volatile. This mean that when the power on the peripheral devices is shut off, the data stored on the medium remain there. This is in contrast to most types of memory, which are volatile. With volatile storage, the data on the medium disappear once the power is shut off.

3.  Removable versus Non removable Media.

In many secondary storage systems, although the peripheral device is online to the computer, the associated medium must be loaded into the device before the computer can read from or write to it. These are called REMOVABLE MEDIA secondary storage systems. Diskette, some types of hard disks, magnetic tape cartridges, magnetic tape reels, and optical disks are examples of removable media used on such systems. Other secondary storage systems, such as those that use Winchester disks are fixed-media secondary storage systems. A Winchester disk system, the disk is encased in a sealed unit within the peripheral device, and it cannot be conveniently removed.

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Floppy Disks

What is a floppy disk??

Floppy disks, often called diskettes or simply disks, are a portable or removable strong media. They are used to store and transport word processing, spreadsheet, and other types of files. Floppy disks are also called floppies because the plastic disk inside the diskette covers is flexible, not rigid. There are several different types of floppy disks; 3.5 inch floppy disks, zip disks, super disks, hifd disks. Floppy disks are inserted into a floppy disk drive, a device that holds, spins, read data from, and write Data TO A FLOPPY DISK. Read means that the data in secondary storage is converted to electronic signals and a copy of that data is transmitted to the computer’s memory (RAM). Write means that a copy of the electronic information processed by the computer is transferred to secondary storage.

Floppy disks have a  write-protect notch, which allows you to prevent a diskette from being written to. To write-protect, use your thumb nail to move the small sliding tab on the lower right side of the disk (viewed from the back), thereby uncovering the square hole. 

On the diskette, data is recorded in concentric circles called tracks. Each track is divided into sectors, invisible wedge shaped sections used for storage reference purposes. Thus data is recorded on  tracks and sectors. 

Three factors determine how much data a given floppy can store, its number of sides, density and format. The capacity of each disk is limited.

DENSITY OF FLOPPY DISKETTE

Floppy disks are removable storage media. The density of a floppy diskette is determined by the amount or volume of it data it can store. Today’s standard is 1.44mb and typically labelled 2HD, which means “two-sided, high-density and can store 1.44 megabytes. The equivalent of 400 type written pages tomorrow’s might be a zip, super disk, or HiFD.

FORMATTING FLOPPY DISKS

Freshly purchased disks have to be prepared or formatted first before they can be used to store any program or data. This process of preparing the disk is called “formatting”. It is during the formatting that the disk storage area is divided into sections (tracks and sectors) electronically. You can equally format an old disk the data on which has become corrupted. If the disk has not been physically damaged, formatting the disk can reclaim all its storage space. However, before this is done it is essential to copy as mmany as possible of the files to other disks, because formatting a disk wipes it clean of any stored data. Formatting a disk is an MS-DOS function. However, different operating systems format disk differently. One operating system cannot read a disk formatted by another.

To format a new disk in DOS, the following steps are necessary.

1.  At the DOS prompt-C:/> type A: and press <Enter>,  the system will display A:/>

2.  At A:/> type FORMAT A:  and press <enter>, the system will be display on the screen “insert diskette to format”.

3.  Insert the new diskette into drive A and press <Enter>; now the system will start checking existing disk format and verifying the size of the disk and finally display the following message on the screen:

Format Complete 

NNNN Bytes Of Disks Space

NNNN Bytes Available On Disk

Format Another Disk (Y/N)?

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How To Handle Diskettes And Floppy Drives

Diskettes are highly sensitive to scratches, to dust, to temperature, to moisture and to magnets. Therefore, 

1. Do not try to store disks any where they could get damp or hot or or cold

.

2. Do not try to force open a disk’s plastic casing or poke anything into it.

3. Do not store disks anywhere near a magnet.

4. Never put disks into a computer’s floppy disk drives before switching on and never turn off the computer with any disk still in a floppy disk drive.

5. Never take a disk out of a drive while the computer is still reading from it or writing from it. (the user can tell if the computer is writing or reading a disk because of the green yellow drive indicator light will either be fully on or flashing ON and OFF).

6. Never open or interfere with the READING WINDOW SHUTTER. Even the grease on one’s hands can damage the data stored on the disk. 

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NEGATIVE IMPACTS OF COMPUTERS

                       

Computers have been said to pose threat to our mental and physical well being (health) and also in our work place and is likely to be that way for many years. We should also be aware of the major concerns raised about the possible effects of computers on our health and work place.

1 Emotional Stress- Emotional problems such as financial worries, feelings of incompetence and disorientation often produce emotional stress.

2 Layoff Or Reassignment- One of the first criticisms levelled at computers upon their entry into the work place was their very presence resulted in job-related   stress. When computers came in, many people were laid off and had to find new jobs. Clerical workers especially worried about job security.

3 Fear Of Falling Behind- The micro computing boom has placed computing power of awesome dimensions at almost everyone’s fingertips. Some researchers perceive a widespread fear that failure to learn how to use these machines will make one ‘’fall behind’’.

4 Burnout- Burnout is caused not by fear of computers but by overuse of them. The infusion off microcomputers into home and office has raised new concerns about what will happen to children and managers who have inadvertently been swept into the tide of the computer revolution.

5 Dangers Posed By Display Device-  Large numbers of data entry operators have reported a variety of physical and mental problems emanating from their interaction with display devices. These includes blurred eyesight, eyestrain, acute fatigue, headaches and backaches.

6 Environment Related Concerns- The surge in the microcomputer has caused variety of environmental concern. The environmental protection agency has estimated the home and office microcomputer systems now annually consume about 82 billion worth of electricity. This indirectly has resulted in the discharge of tons of pollutants into the atmosphere.

7 Social Related Worries- The future generations have relied on compeers so much that they lose sight of fundamental thought processes that computers are intended to model. Many teachers complain that some children who own pocket calculators can’t do arithmetic by hand. There is no question, of course, that computer has altered the structure of work and play just as mechanised farm machinery changed the nature of agriculture airplanes and automobiles changed the nature of travel. Many people have accepted these disruptions as the price of ‘progress’. 

8 Computer Crime- Computer crime is defined as the use of computers to commit unauthorized acts. It has many forms. Some cases involve the use of computer for theft of financial assets, such as money or equipment. Other concern the copying of information- processing resources such as program or data to the owners detriment. Still other cases involve manipulation of data such as grades of personal advantage.  The cost of computer crime to individuals and organization is estimated at billions of dollars annually in addition to undetected or unreported incidents and is hard to pin down. Some of the specific forms of computer crime can take are:

Data digging, super zapping, scavenging, trapdoors, logic bombs and computer viruses, data leakage, software, piracy.

 

9 Computers And Privacy- Privacy refers to how information about individuals is used and by whom. We can appreciate that sometimes selected people or organizations have a legitimate need for some of this information.

A doctor needs accurate medical history of patients. A company or government may need to probe into the lives of people applying for unusually sensitive jobs. No matter how legitimate the need, however, once personal information has been made available to others, there is always the danger that it will be misused.

The problem of how to protect privacy and ensure that personal information is not misused was with us long before electronic computers existed. But modern computer systems, with their ability to store and manipulate unprecedented quantities of data and to make those data available to many locations have added a new dimension to the privacy issue. The greater the ability to collect, store, use, and disseminate information, the greater the potential for abuse of that information.

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