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Operating Systems

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Operating Systems An operating system is a set of programs designed to run in the background on a computer system, giving an environment in which application software can be executed. Most operating systems comprise a large set of programs, only some of which are stored in the processor memory all the time. Many of the routines available in the O.S. are stored on the hard drive so that they can be accessed when required. This not only saves space in the processor memory but also means that the O.S. can be easily changed to a different one. When a user is using an application package, he is not communicating with the computer hardware, he is communicating with the operating system. Without an operating system, no matter how many programs the user have, the computer is useless. The operating system sits between the hardware and the application program or user. The main purpose of an operating system is to allow a user to access the hardware so they can carry out useful tasks. Breaking down the operating system: Functions of the operating systems. For computers generally: * Memory Management: allocation of program space, buffers, swapping, storage protection * Processor Management: scheduling of programs awaiting processing, queue handling, priority allocation, interrupt handling * Resource Management: control of hardware resources e.g input and output devices, interacting with peripheral control units, handshaking * Data Management : control of disc filing system, loading programs and data, spooling, error handling, maintaining directories Types of Operating System * Batch Processing When computing was still a new science, there were not enough machines to satisfy the demand for processor time from students in universities who wanted great calculations done, firms who wanted their payroll worked out, and many others. The big problem was the 'speed mismatch' between the user sitting at the keyboard who was very slow, and the machine which was very fast. ...read more.


Novice: These users have some experience of working with computers, but may be unfamiliar with a new system. They are liable to make mistakes because of their limited experience. Most of the users of a new system will start as a novice. Skilled: Users who have considerable expertise using the system. Most of the users become skilled due to frequency of use. They will be able to operate the system efficiently, but will have limited knowledge or no knowledge about the structure of the system. They will not be able to solve unexpected errors. Expert: Users who have thorough knowledge about the working of the system and their internal structure. They will have the ability to maintain and modify the basic system. Types of User Interface Communication between a user and a computer is two-way. A user will give data and instructions to a computer and a computer will give information back to a user. The may that a computer and a user communicate is known as the 'interface'. Another common term is Human-Computer Interface or HCI. There are different types of interface, which are useful in different situations and for different types of user. * Form based If the majority of the input to a system is of a standard type, in other words the computer knows what sort of input to expect, then a typical interface will produce a form on the screen to be filled in. This sort of interface would be used where an operator is inputting information while asking a customer questions over the telephone. The interface * prompts the operator to ask all the questions * makes the operator input the information in the correct order * ensures that the information is input in the correct format by having specific areas to input the data * makes the checking of the information easier. The characteristics of a form based interface are that * There are field names, names next to a place where information must be entered * There are places called 'response fields' where information is entered by the user. ...read more.


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 "so that you can get around the system" are perfectly acceptable. System Software James Leong Mook Seng 1 ...read more.

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