Operating Systems Essay

Interfaces that are graphical in nature are known either as Graphical User Interfaces(GUI) or WIMP interfaces (Windows, Icons, Menus and Pointer). Typically, these types of interfaces are available in multi-programming environments or in applications software that involve a considerable degree of complexity. In a GUI, there are: A ‘window’ for each open application. Many windows can be open at the same time but only one window can be active at any one time. There may be some way of indicating which one is active (perhaps by making the bar at the top of the active window blue). Menus and icons. Available functions can be selected in one of two ways, either by using pop-up menus or drop-down menus, or clicking on ‘icons’. An icon is simply a small picture that represents a specific function- clicking on it selects that function.   A pointing device, usually a mouse but in certain circumstances a graphical tablet and pen can be used. These are used to make selections.   The use of the keyboard to navigate through the application is minimized because it is relatively time-consuming way of working.   Natural language. Natural language interfaces are those that allow the user to communicate in their native language, such as English. It allows the user to instruct the computer without need for a particular ‘syntax’. The system needs to be able both to interpret inputs in natural language from the user, and to act upon them, and, also preferably to generate natural language statements in response to user input. Sometimes it is also referred as a conversational interface. The questions are displayed on the VDU and the answers are entered via the keyboard. For example, imagine a user has initiated a ‘save file’ request. The ‘conversation’ might be: COMP:What’s the file name? USER: chapter1. txt COMP:what folder? USER: userguide COMP:File already exists. Overwrite? USER:Yes COMP: Done. This kind of interface can be found on data entry terminals and other types of dumb terminals connected to a network where non-experts users are guided through the complex tasks they need to perform by the computer.   Command line Command based interface is one where the user types a series of commands at the keyboard which tell the computer what their intentions are. It is also known as linguistic manipulation. The characteristics of a command based interface are   the user needs to know what commands are available   the user needs to understand the commands Characteristics of a command based interface 1) The system is very much more open than in the other types of interface. Other interfaces restrict the options that the user has available to them. This can be particularly important for the system manager because different users can only be allowed to have access to specific parts of the system. 2) Command based interfaces can only be used by computer literate people because the user need to understand the commands and their uses. 1. Define what is meant by the term operating system. (2) 2. Give two reasons why an operating system is likely to be stored on backing storage rather than in the memory of the computer. (2) 3. Distinguish between a multi-programming and a multi-access operating system. (2) 4. State what is meant by a distributed system, and give an advantage of this type of multi-access system over a simple network of machines. (2) 5. A computer operator takes phone calls from the public who ring up asking whether a particular item in a catalogue is available. The operator needs to type in a series of responses to questions put to the caller, so that the computer can check the file and determine whether there are any of that item available. Design a screen interface that would be suitable for the operator to use. (4) 6. The technician responsible for maintaining the system in question 5, uses a command line interface. a) Explain what is meant by a command line interface. (2) b) Give two advantages and one disadvantage to the technician of using a command line interface rather than a menu based interface. (3) Answers: 1 A. -A (suite of) programs†¦-which run the basic functions of the computer†¦ -giving an environment in which to run application software. A question which begins with the word define, leaves very little room for manoeuvre because it is asking for a standard answer. This is not an opportunity to show your prowess by making up an answer that is original- there aren’t any. Note, also, the fact that three answers have been given. Always try to give one more answer than seems to be required by the question. If you look at a mark scheme for an examination paper, the mark points are listed as a set of bullet points so there is no reason why you should not do the same. This style of answer helps you to write down your thoughts easily without getting confused by the language. The purpose of this examination is not to test your ability with English, rather to test your knowledge of computing. 2 A. – A full operating system requires a large amount of storage space that is better utilised in the computer memory for applications – Storage of the operating system on backing storage allows for easy upgrading or changing from one system to a different one. Note that the temptation to call the operating system the O. S. has been resisted in the answer. In general, do not use abbreviations in your answers. There are exceptions, where the abbreviation is the accepted form, but your own versions may be ambiguous or, even, not understood by the examiner. If you do need to use an abbreviation, because the term is to be used a number of times, give the term in full with the abbreviation that you want to use in brackets after it. For example, the first time that you use the term operating system write â€Å"†¦ operating system (OS)†¦ † you can then use OS as often as you like in the rest of your answer. 3. A. – A multi-programming operating system is one where the user of the machine is given the impression that they can carry out more than one task at a time. – A multi-access operating system is one where it is possible for more than one user to access the system apparently at the same time. Note that there are a large number of points that could have been made about both of these operating systems, but most of them would not answer the question. It is important when answering a question starting with ‘distinguish’ to choose facts that show a comparison. 4 A. – A distributed system is one which uses many storage locations on different machines to store software and files. – Access to files can be speeded up because more than one file command can be carried out at a time. When an advantage is asked for it is normal to state in the question, either explicitly or implicitly, with what the comparison should be made. Be careful to give an advantage using this comparison and not a more generalised one. 5 A. – Form type interface – Catalogue number – Space for the description of goods which will be filled in by the computer itself – Spaces for computer to produce availability and price – Laid out with spaces for input. What is just as important here are the things that would not be on the screen. The question makes it quite clear that there is no ordering going on, so spaces for name and address, or method of payment, are not only going to score no marks, but will probably be penalised because they demonstrate that the candidate has not understood the question. In this type of question it is important to demonstrate that you have taken the situation into account. 6 A. a)-Series of commands typed at a screen prompt†¦ -which give specific instructions to the computer. b)Advantages: -Entire system is available to the technician -Access to the particular part of the system required is gained more quickly than using other types of interface. Disadvantage: -The technician needs to know the commands that are available -The technician needs to understand the way the system is designed so that it can be navigated efficiently. Note. The language used in this answer is not the sort of language that a candidate will use in an examination. Don’t worry about this. Answers like â€Å"so that you can get around the system† are perfectly acceptable. System Software James Leong Mook Seng.