Thursday, March 4, 2010
• Real-time Operating Systems
• Multi-user and Single user Operating systems
• Multi-tasking and single-tasking Operating systems
• Distributed Operated systems
• Embedded Operating system
It should however be noted that a particular OS may employ characteristics of two or more types of OS to maximise functionality and portability. At this point I would opt to write about multi-user operating systems.
A multi-user operating system ensures that more than one user operates the computer system at any one particular time. Resources of the computer system are so managed in a way that allows for speedy execution of operations by any one user in a way that gives an individual user the impression that he/she is the only one using the computer system at that particular time.
From the above, one is correct to bear in mind that for such an OS to work properly, the system must have good computing speed to ensure maximum computer time for each individual user, possess enough system memory to store the operations of each user, proper networking of the workstations involved (though some systems have done away with the use of workstations and instead operates using user accounts existing on the same system).
Use of a multi-user OS comes with a number of advantages such as reduction in hardware and software cost through shared resources, better system control through use of usernames and passwords that improves system security, though system breach becomes far more costly.
To end, it is worth mentioning that many of the popular operating systems available today are examples of multi-user OS. These include the Apple’s Mac OS, Microsoft’s Windows and almost all the UNIX distributions including Linux, Sun’s Solaris, etc.
Slater, Robert, Portraits in Silicon, MIT Press, Cambridge, 1992.
The UNIX OS can be said to have been a major player in the development of the internet due to its unique environment and server-client model. Its popularity also arose principally from the fact that it was freely distributed. Currently, many UNIX derivatives are distributed both freely and commercially.
Made up of the Kernel, file system and the command-line interface called the shell, UNIX boasts of more than 600 commands enabling users to manipulate data in any conceivable way. The above noted, UNIX has many advantages that makes it the best operating system to use.
Regarding cost, UNIX can be said to be very cost effective since it exists in both freeware and commercial distributions. This makes it better than the totally commercialised operating systems that exist today, for instance windows.
In matters of portability, none compares with the UNIX system. Because of the many distributions of different versions of UNIX, such as Linux (which also comes in many distributions) Sun’s Solaris, etc, one can easily use programs designed for one distribution in other distributions and not have to worry about efficiency. Currently, with the embedding of winetools in the source code of many UNIX distributions, many application software developed especially for the windows platform can now be used by UNIX users.
Because UNIX is freeware, it makes available source codes to people who intend to adapt them for personal use or in the name of education. This cannot be said for licensed OS like Windows which makes it a crime to edit its (window’s) source code. Because of that, one can always expect better output from the UNIX because there are so many people working to make it better to use.
Security is also better in a UNIX system than many other operating systems. Because of the compact layers of the UNIX kernel and the command-line Shell which requires that only the administrator with Super User (SU) privileges can change system parameters, it is very difficult to encounter security breaches from malware and unauthorised access.
Finally, it is worth noting that gone are the days when the UNIX shell scared a lot of people from using UNIX. Now with the incorporation of the motif GUI in many UNIX distributions, including Linux, it has become user friendly yet maintaining its security. No wonder the increasing popularity UNIX distributions, such as Linux, enjoy presently.
Slater, Robert, Portraits in Silicon, The MIT Press, Cambridge, 1992.
http://www.unix.org/what_is_unix.html The Open Group, 28 December 2003, 11-02 -2010
http://www.unix.org/whitepapers/uos.pdf, the Open Group, 11-02-2010
Thomas Hobbes is of the view that man is exclusively selfish in all his actions and is not likely to perform any action if such an action will be of no benefit to him. It is on this premise that Hobbes begins his discussion on the causes of quarrel in the human society.
It is worth noting that in Hobbes’ view, there is in practice nothing which is objectively good or bad, but that there are only things which a person desires and that which he averts, representing good and bad, respectively.
Moving on to the causes of quarrel, Hobbes gives three main reasons why there is conflict in society, namely competition, diffidence and glory. But it worth noting that the proper context where the three causes promote conflict is found in Hobbes’ psychological theory where he states that
a. the individual is psychologically selfish,
b. the individual’s greatest desire is self preservation
c. the individual’s greatest aversion is death.
Again it is worth considering the two laws of nature (namely seeking peace in order to follow it and defending oneself by all means) and how they affect the individual’s desire for self-preservation and his aversion of death.
Considering competition as a cause of quarrel, Hobbes makes it known that nature has made all people equal in the powers they need to exist. But there is the selfish inclination within man to try to maximize his happiness, which is nothing else than the level of success one has in self-preservation. Hence he invades others for gain, leading to quarrel.
For reasons of safety, an individual may be forced to confront others. This is called diffidence. Should any threat, imagined or real, arise to cause fear in an individual’s desire to maximize his happiness, he is forced to counter that threat through any means necessary, hence quarrel with the object of his aversion.
Finally, because of man’s selfishness, he tries to assert himself over others. He thus looks for means to achieve glory which is nothing else but quest for reputation. When and individual does not wish to remain on equal terms with others, he resorts to all manner of actions to assert himself over them. Thus glory becomes a cause of quarrel taking into account that man is naturally selfish.
In conclusion, without the presence of a sovereign who would provide the needed balance to every individual’s desire, the probability is high that every person will quarrel with his neighbour, given that confrontations may arise out of desire for self preservation, aversion to fear in favour of safety or to seek glory.
- Pure silicon is not a conductor because in its pure state its electrons are bonded tightly with the electrons of other neighbouring silicon atoms in such a way that it requires a relatively large increase in energy levels to cause electrons to break from the valence band into the conduction band.
- When silicon is doped with phosphorus, the result would be that an excess of one electron is created on the valence band of the doped silicon atom. Since the valence band of an atom takes up to eight (8) electrons, there would exist one free moving electron which can easily jump into the conduction band, thus constituting flow of electrical current.
- The main difference between a P-type silicon and an N-type silicon exists in what material was used to dope the silicon. Should the silicon undergo a Trivalent doping, using an element with a valence band consisting of 3 electrons (eg boron) there would exist one empty spot on the shell after the two elements are bonded thus leading to the formation of a P-type silicon. It is P-type (positive) because it lacks one more electron to complete its valence band.However should silicon be doped with a pentavalent element, (thus an element with 5 electrons on its valence band) there would exist an excess electron on the valence shell after the two elements bond. This excess electron, which is free moving, thus has the capacity to jump the gap into the conduction band.
A diode, being a device which allows electric current to flow in one direction is made up of a P-type and an N-type silicon arranged adjacent each other, leaving a thin film of space called the depletion region connected to an energy source. It is in the arrangement of the energy source in the circuit which dictates in which direction current flows.
In a forward biased diode, there exists a positive voltage across the diode from the P to N type silicon. This enables the diode to act like a good conductor hence allowing current to flow in one direction.
However, when the polarity in the energy source is changed so that there is almost no flow of current then one has a reverse-biased diode. This causes the diode to become almost non-conducting and measures a large amount of voltage across the devise.
The State of Nature is, in Hobbes’ view, the state in which man lived with other men before the emergence of the civil society or the commonwealth. He, however, lays no claim on the actual historical existence of a state of nature, but rather that the state of nature exists in any place or time where civil society is not functioning.
The workings of the state of nature can be understood in its proper context when one takes into account the psychological theory of Hobbes which makes the following assertions, namely, that man is psychologically egoistic and would do nothing except from selfish motives; that there exists no objective good or bad except those things a person desires, which he considers good and those things he averts which he considers bad and those things which he has contempt for, which he considers vile; that the highest desire of man is self-preservation and his worst aversion is death and; that all people are equal in their natural means of attaining the objects of their desire, and this, he terms power . Thus, Hobbes makes the claim that in the state of nature, happiness is judged only by the amount of success he has in pursuing the object of his primary desire, namely, self preservation.
Again, Hobbes makes the claim that morality is nothing apart from the will of the sovereign. Thus, if there exists no sovereign to promulgate laws for the general conduct of the people, there would exist no ethical code, hence no morality. One could even make the concession that the only law of morality is that of self-preservation which necessitates the use of all measures to ensure that the individual protects him/herself from any and all things which he considers a threat to his wellbeing irrespective of how negatively such measures may affect others.
From the above, it is perceived that in the state of nature, conflict is a common feature. This stems from the fact that all individuals are equipped with the same natural powers to achieve self preservation. But since every individual is selfish and not restrained by any central authority though each has to protect himself using the same powers, they are each equally capable of inflicting injury on their neighbours, hence conflicts.
Finally, in the state of nature, there is anarchy. Morality is primarily dictated by the desire for self-preservation which is itself a product of vital and voluntary motion. In the absence of a sovereign, individuals lack that awareness which reason imparts on their actions. Thus, in Hobbes’ view, without any law to restrain people’s actions there would be total lawlessness since each person would only act in order to maximize happiness .
BONEVAC, Daniel, Today’s Moral Issues, (3rd ed.), Mayfield Publishing Company, California, 1999.
KOLAK, Daniel, Questioning Matters, Mayfield Publishing Company, California, 2000.
WHITE, James E., Contemporary Moral Problems, (5th ed.) West Publishing Company, New York, 1997.