Saturday, July 24, 2010
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Thursday, July 22, 2010
Advantages and Disadvantages of Computers
Computer has many pros and cons, as every object in this world has. It's advantages and disadvantages are listed below:
Advantages
a) Computers are 100% accurate and much more reliable than any other devices and human beings.
b) Computer is much faster than human
c) It is very much useful for repeated jobs, which is difficult and tedious for human to do.
d) With the help of computer, impossible things are easy to show and simulate.
e) It is versatile and can perform various types of works.
f) It can be used in multiple fields so it is called general purpose machine.
g) Because of the availability of storage, programs can be modified to add features for different purpose.
Disadvantages
a) It is expensive and is beyond the reach of poor people. This limitation is being overcome because its cost is drastically decreasing day by day.
b) It is electronic machine, so there is much danger of electric shock and other physical damages.
c) Since it is much reliable, sometimes the failure in devices and programs can produce unreliable information and cause loss of data in a great extend.
d) It increases dependency on machine. Even for very simple calculation people need them.
e) Although it helps in faster and cheaper communication, there is much danger of security leakage by third party by which authentication becomes questionable.
f) In underdeveloped countries like Nepal, it increases piracy of intellection properties in big volume.
g) Since computers are used in sensitive areas like natural defense, civil aviation, banking, so even a simple mistake can cause loss of life and property.
Advantages
a) Computers are 100% accurate and much more reliable than any other devices and human beings.
b) Computer is much faster than human
c) It is very much useful for repeated jobs, which is difficult and tedious for human to do.
d) With the help of computer, impossible things are easy to show and simulate.
e) It is versatile and can perform various types of works.
f) It can be used in multiple fields so it is called general purpose machine.
g) Because of the availability of storage, programs can be modified to add features for different purpose.
Disadvantages
a) It is expensive and is beyond the reach of poor people. This limitation is being overcome because its cost is drastically decreasing day by day.
b) It is electronic machine, so there is much danger of electric shock and other physical damages.
c) Since it is much reliable, sometimes the failure in devices and programs can produce unreliable information and cause loss of data in a great extend.
d) It increases dependency on machine. Even for very simple calculation people need them.
e) Although it helps in faster and cheaper communication, there is much danger of security leakage by third party by which authentication becomes questionable.
f) In underdeveloped countries like Nepal, it increases piracy of intellection properties in big volume.
g) Since computers are used in sensitive areas like natural defense, civil aviation, banking, so even a simple mistake can cause loss of life and property.
Batch systems
A batch system is one in which jobs are bundles together with the instructions necessary to allow them to be proposed without user intervention.
The simple operating system also called monitor is system software responsible for interpreting and carrying out the instructions in the batch jobs. When the monitor started a job, it is finished. Such batch system is called stacked job or simple batch system.
Often magnetic tapes and drums were used to store intermediate data and compiled programs.
1. Advantages of batch systems
Ø Move much of the work of the operator to the computer
Ø Increased performance since it was possible for job to start as soon as the previous job finished
2. Disadvantages
Ø Execution time can be large from user's point of view.
Ø Due to lack of protection scheme, one batch job can affect pending jobs
Ø A job could corrupt the operating system thus may affect pending jobs
One difficulty with simple batch simple batch systems is that the computer still needs to read the deck of cards before it can begin to execute the job. This means that the CPU is idle (or nearly so) during these relatively slow operations.
Capabilities and Limitations of Computer
Computer is a device, which is capable of doing almost all the works, which can be programmed by the user. But there are some functions, which are impossible for a computer to perform. Following are some of the capabilities and limitations of computer:
Capabilities
(a) Computers can do jobs with 100% accuracy and in a very fast speed in comparison to any other devices or human.
(b) It is possible to show and do the things, which are impossible for humans.
(c) Computer provides faster and cheaper communication with the use of various commutation technologies.
(d) it can perform almost all the works but for any purpose, user must provide proper program and necessary hardware.
Limitations
(a) Computer is a dull machine. It doesn't have intelligence on it. So, whatever it does, that is with the help of programs and devices developed by human. If such assistances are not provided, it will not be able to perform the simple of the simplest works, too. If any error occurs in its structure or circuitry, then the output (result) given by it is wrong which is very hard to tackle . It can't distinguish between the good and bad inputs and outputs in comparing to human. So, it is often called 'idiot servant'.
The simple operating system also called monitor is system software responsible for interpreting and carrying out the instructions in the batch jobs. When the monitor started a job, it is finished. Such batch system is called stacked job or simple batch system.
Often magnetic tapes and drums were used to store intermediate data and compiled programs.
1. Advantages of batch systems
Ø Move much of the work of the operator to the computer
Ø Increased performance since it was possible for job to start as soon as the previous job finished
2. Disadvantages
Ø Execution time can be large from user's point of view.
Ø Due to lack of protection scheme, one batch job can affect pending jobs
Ø A job could corrupt the operating system thus may affect pending jobs
One difficulty with simple batch simple batch systems is that the computer still needs to read the deck of cards before it can begin to execute the job. This means that the CPU is idle (or nearly so) during these relatively slow operations.
Capabilities and Limitations of Computer
Computer is a device, which is capable of doing almost all the works, which can be programmed by the user. But there are some functions, which are impossible for a computer to perform. Following are some of the capabilities and limitations of computer:
Capabilities
(a) Computers can do jobs with 100% accuracy and in a very fast speed in comparison to any other devices or human.
(b) It is possible to show and do the things, which are impossible for humans.
(c) Computer provides faster and cheaper communication with the use of various commutation technologies.
(d) it can perform almost all the works but for any purpose, user must provide proper program and necessary hardware.
Limitations
(a) Computer is a dull machine. It doesn't have intelligence on it. So, whatever it does, that is with the help of programs and devices developed by human. If such assistances are not provided, it will not be able to perform the simple of the simplest works, too. If any error occurs in its structure or circuitry, then the output (result) given by it is wrong which is very hard to tackle . It can't distinguish between the good and bad inputs and outputs in comparing to human. So, it is often called 'idiot servant'.
Analog computer
The Computers, which work with the natural phenomena and physical values like frequency, earthquake, volcano, water flow, current flow etc, are known as analog computers. They are based on continuous changing values or voltage levels. These types of computers are used in scientific work, commercial and personal purpose. Examples of analog computer some of its characteristics are presented below:
1. Based on continuous varying data.
2. Measure only natural or physical values.
3. Used for special purpose.
4. Generally, no storage facility is available because they work on
real time basis. If provided, then only a little amount of storage
is available in it.
5. Accuracy of these types of computers is very less because of
noise and Filtering facility. Increasing accuracy is costly.
6. Output of that signal sis also not well known by general public
because They are in form of wave lines, curved lines or grapes.
7. The wave form of analog signals is represented in figure below.
1.1o.2.2 Digital Computer: - These computers are based on discrete quantities and are represented with binary numbers. They are based on binary digits. Binary system is such system of numbering in which only 2 digits are used 0 and 1. Meaning of 0 is either OFF; FALSE, NO etc and 1 is ON, TRUE, YES etc. So the basic principle of these computers is either present or absence of electrical pulses in the signals, Examples of these computers are IBM PC, Apple/Macintosh etc. Some major characteristics of these computers are listed below:
1. Based on discrete data which are not continuous with time.
2. Based on principle of logic 1 and 0 (high and low voltage).
3. Used for general purpose.
4. They are more reliable because of less noise and filtering facility.
5. It has large memory capacity because the calculations are to be stored
internally for future use and re-programming.
6. It is multipurpose and programmable, so, it is of high cost and faster
Processing.
1. Signal representation of digital pulses is shown in figure below.
1.10.2.3 Hybrid Computers
Hybrid means combination or cross-link of two or more types. So, as the name suggests, it is combination of analog and digital computers. It can perform the works done by analog computers as well as digital computers, examples of these types of computers are: computers used in hospitals, computers used in jet planes etc. The best example of hybrid device is Modern. It consists of both analog and digital parts. Some other major characteristics of these computers are presented below.
1. Combination of good qualities of analog as well as digital computer.
2. Can process both continuous and discrete data. It has capacity to convert one type of data into another.
3. These are special purpose machine.
4. Mostly used in airplanes, hospitals etc.
5. High cost.
c) On the basis of brand
- IBM Computer
IBM, which was established by Dr. Herman Holleith in 1923 AD, is the largest computer manufacturing company in the world till today. It was leading the market of mainframe and PCs. Nowadays it uses the processors, multimedia devices and some other hardware parts developed by some other companies like Intel but use the principle of its own. So, all the computers developed by IBM company are called IBM computers, it has two categories; a) IBM PC and b) IBM compatible. The computers developed by IBM company itself are called branded or IBM PC. Computers which are developed or assembled by other companies using the parts and principle of IBM PCs are called IBM compatibles. So, IBM compatibles are also called duplicate of IBM PCs.
- Apple/Macintosh Computer: - Apple Corporation was established in 1970 AD in USA. By far it has gone much forward and produced PCs with good qualities and user friendly. So, all the computers that are developed by Apple Corporation are called Apple/ Macintosh (Mac) computers. These computers are architecturally totally different. Software made of IBM's not only hardware part, but their software architecture is also totally different. Software made for IBM PC can't be run in Macintosh or vice versa. Floppy disks or hard disks formatted in one can't be recognized by other. Before 2006 they used power PC processor like G3, but nowadays they are using Intel processor.
d) On the basis of model
- XT Computer: - XT (eXtra Technology) Computers are the old technology computers with much slower processing speed (not more than 4.77 Mhz). Advanced GUI based software like (Windows) can't be run in these computers. Everything was based on text based system. Serial number of processors was like 8086, 8088 which were developed bye Intel and were 16 bit world length. Complex calculation and large processing couldn't be done. I/O devices were not flexible and faster.
- AT Computer: - AT (Advanced Technology) computers are the new technology computers. They are faster in processing than XT and can run any type of software whether that is text based or GUI based. Serial number of processors is 80286, 80386, 80486, Pentium1, Pentium 2 etc. Any type of complex and long processing can be done depending on the capacity of the computers. I/O devices are interactive, flexible and faster. Word length exceeds 16 bits. Co-processors are used to help the main processors for complex mathematics.
- PS/2 Computer: - Actually, these are not totally different models of computers but are refinement of AT computers. These models were built after 1990s and mostly used in laptop computers. Rechargeable and battery operated systems with faster and flexible I/O devices are some important characteristics of these computers. OS/2 operating system was used at the beginning but now-a-days, windows operating system is leading.
e) On the basis of purpose
- General purpose Computers: - The computers that can be used for verities of purpose are called general purpose computers. The general purpose computers can be used for word processing, spread sheet applications, multimedia applications, publications etc. The desktop computers are considered as the general purpose computers because they can be used for verities of applications.
- Specific purpose Computer: - The Computers that are used for some specific applications are called specific computers. The computers that are used to control the traffic light, the single chip computers used in automatic systems such as microwave oven, television set, automatic air conditioning systems and many other automatic systems are specific purpose computers. They are called specific purpose computer because they are used for one or some limited purpose.
i) George Boole: One of the greatest achievements of 19th century was the discovery of mathematical logics called 'Boolean Algebra'. He studied and presented the symbolic logics which are the foundation of modern computers. His logics provided basic idea of presenting the electric circuits with binary inputs (0 or 1) and its output.
(J) Dr. Herman Hollerith: He was a census statistician in Us bureau of statistics. He is remembered in the history of computers for the following contributions:
Operating system
Definition
The operating system is defined as set of programs that control the entire operation of the computer such as handling inputs/Output operation, user request, interrupts etc the operating system manages the resources of a computer system and schedules its operation. It is a master supervisory program which provides a friendly interface for the user to interact with the computer and its peripherals and different application software as well as an environment for program to execute.
Types of operating systems
Based on the technological development operating system can be divided as follows:
1. Based on continuous varying data.
2. Measure only natural or physical values.
3. Used for special purpose.
4. Generally, no storage facility is available because they work on
real time basis. If provided, then only a little amount of storage
is available in it.
5. Accuracy of these types of computers is very less because of
noise and Filtering facility. Increasing accuracy is costly.
6. Output of that signal sis also not well known by general public
because They are in form of wave lines, curved lines or grapes.
7. The wave form of analog signals is represented in figure below.
1.1o.2.2 Digital Computer: - These computers are based on discrete quantities and are represented with binary numbers. They are based on binary digits. Binary system is such system of numbering in which only 2 digits are used 0 and 1. Meaning of 0 is either OFF; FALSE, NO etc and 1 is ON, TRUE, YES etc. So the basic principle of these computers is either present or absence of electrical pulses in the signals, Examples of these computers are IBM PC, Apple/Macintosh etc. Some major characteristics of these computers are listed below:
1. Based on discrete data which are not continuous with time.
2. Based on principle of logic 1 and 0 (high and low voltage).
3. Used for general purpose.
4. They are more reliable because of less noise and filtering facility.
5. It has large memory capacity because the calculations are to be stored
internally for future use and re-programming.
6. It is multipurpose and programmable, so, it is of high cost and faster
Processing.
1. Signal representation of digital pulses is shown in figure below.
1.10.2.3 Hybrid Computers
Hybrid means combination or cross-link of two or more types. So, as the name suggests, it is combination of analog and digital computers. It can perform the works done by analog computers as well as digital computers, examples of these types of computers are: computers used in hospitals, computers used in jet planes etc. The best example of hybrid device is Modern. It consists of both analog and digital parts. Some other major characteristics of these computers are presented below.
1. Combination of good qualities of analog as well as digital computer.
2. Can process both continuous and discrete data. It has capacity to convert one type of data into another.
3. These are special purpose machine.
4. Mostly used in airplanes, hospitals etc.
5. High cost.
c) On the basis of brand
- IBM Computer
IBM, which was established by Dr. Herman Holleith in 1923 AD, is the largest computer manufacturing company in the world till today. It was leading the market of mainframe and PCs. Nowadays it uses the processors, multimedia devices and some other hardware parts developed by some other companies like Intel but use the principle of its own. So, all the computers developed by IBM company are called IBM computers, it has two categories; a) IBM PC and b) IBM compatible. The computers developed by IBM company itself are called branded or IBM PC. Computers which are developed or assembled by other companies using the parts and principle of IBM PCs are called IBM compatibles. So, IBM compatibles are also called duplicate of IBM PCs.
- Apple/Macintosh Computer: - Apple Corporation was established in 1970 AD in USA. By far it has gone much forward and produced PCs with good qualities and user friendly. So, all the computers that are developed by Apple Corporation are called Apple/ Macintosh (Mac) computers. These computers are architecturally totally different. Software made of IBM's not only hardware part, but their software architecture is also totally different. Software made for IBM PC can't be run in Macintosh or vice versa. Floppy disks or hard disks formatted in one can't be recognized by other. Before 2006 they used power PC processor like G3, but nowadays they are using Intel processor.
d) On the basis of model
- XT Computer: - XT (eXtra Technology) Computers are the old technology computers with much slower processing speed (not more than 4.77 Mhz). Advanced GUI based software like (Windows) can't be run in these computers. Everything was based on text based system. Serial number of processors was like 8086, 8088 which were developed bye Intel and were 16 bit world length. Complex calculation and large processing couldn't be done. I/O devices were not flexible and faster.
- AT Computer: - AT (Advanced Technology) computers are the new technology computers. They are faster in processing than XT and can run any type of software whether that is text based or GUI based. Serial number of processors is 80286, 80386, 80486, Pentium1, Pentium 2 etc. Any type of complex and long processing can be done depending on the capacity of the computers. I/O devices are interactive, flexible and faster. Word length exceeds 16 bits. Co-processors are used to help the main processors for complex mathematics.
- PS/2 Computer: - Actually, these are not totally different models of computers but are refinement of AT computers. These models were built after 1990s and mostly used in laptop computers. Rechargeable and battery operated systems with faster and flexible I/O devices are some important characteristics of these computers. OS/2 operating system was used at the beginning but now-a-days, windows operating system is leading.
e) On the basis of purpose
- General purpose Computers: - The computers that can be used for verities of purpose are called general purpose computers. The general purpose computers can be used for word processing, spread sheet applications, multimedia applications, publications etc. The desktop computers are considered as the general purpose computers because they can be used for verities of applications.
- Specific purpose Computer: - The Computers that are used for some specific applications are called specific computers. The computers that are used to control the traffic light, the single chip computers used in automatic systems such as microwave oven, television set, automatic air conditioning systems and many other automatic systems are specific purpose computers. They are called specific purpose computer because they are used for one or some limited purpose.
i) George Boole: One of the greatest achievements of 19th century was the discovery of mathematical logics called 'Boolean Algebra'. He studied and presented the symbolic logics which are the foundation of modern computers. His logics provided basic idea of presenting the electric circuits with binary inputs (0 or 1) and its output.
(J) Dr. Herman Hollerith: He was a census statistician in Us bureau of statistics. He is remembered in the history of computers for the following contributions:
Operating system
Definition
The operating system is defined as set of programs that control the entire operation of the computer such as handling inputs/Output operation, user request, interrupts etc the operating system manages the resources of a computer system and schedules its operation. It is a master supervisory program which provides a friendly interface for the user to interact with the computer and its peripherals and different application software as well as an environment for program to execute.
Types of operating systems
Based on the technological development operating system can be divided as follows:
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