1.2 System software is a set of one or more programs, design to control the operation and extend the processing capabilities of a computer system. It designed to operate the computer hardware and to provide and maintain a platform for running application software.
[System software includes Operating system, compilers, servers, windowing systems, utilities, language translator, data communication program, data management program and more like
- Loaders
- Linkers
- Utility software
- Desktop environment / Graphical user interface
- Shells
- BIOS
- Boot loaders ]
The most important types of system software are:
- The operating system (prominent examples being Microsoft Windows, Mac OS X and Linux), which allows the parts of a computer to work together by performing tasks like transferring data between memory and disks or rendering output onto a display device. It also provides a platform to run high-level system software and application software.
- Utility software, which helps to analyze, configure, optimize and maintain the computer.
- Programming Language Translators: Programming language translators are system software, which transform the instructions prepared by programmers in a programming language, into a form, which can be interpreted and executed by a computer system. Programming language translators are: Compilers, Interpreter and Assemblers.
- Communication Software: In a Network environment, communications software enables transfer of data and programs from one computer system to another.
- The computer BIOS and device firmware, which provide basic functionality to operate and control the hardware connected to or built into the computer.
1.2.1: Operating System: It is an integrated set of programs that controls the resources (CPU, Memory, I/O devices etc) of a computer system and provides its users with an interface or virtual machine that is more convenient to use than the bare machine.All computers have operating systems. The most common are the Windows family of operating systems developed by Microsoft, the Macintosh operating systems developed by Apple and the UNIX family of operating systems (which have been developed by a whole history of individuals, corporations and collaborators). There are hundreds of other operating systems available for special-purpose applications, including specializations for mainframes, robotics, manufacturing, real-time control systems and so on.
User Interface: The term “user interface” originated in the engineering environment in the late 1970s. Virtually every one who interacted directly with computers had been engineers and programmers, but a new kind of users, were emerging the non-programming user. These users often reacted more negatively to difficulties in dealing with a machine. New forms of interaction was needed new interfaces, were required attention flowed to “the user interface”.
GUI: It includes tool-kits and frame works. Most of these toolkits are based on object oriented approach. GUI interface has become a standard component of most systems, no standards in windowing systems, imaging models APIs or high level toolkits have emerged.
GUI terms are as follows
i. Bit Mapped Displays: It display made up of tiny dots (pixels) that are independently addressable and much finer resolution than character displays. ii. Pointing devices iii. Windows: that graphically displays what the computer is doing. iv. Menus: it display a list of commands available with in an application. From this menu, the end user can select operation such as file, edit, search etc.
v. Icons: that represents files, directories and other application and system entities.
vi. Desktop Metaphor : In it users are not aware of applications. Users deal with files, folder, drawers, a clip board and an out-box. vi. Dialog boxes, button, sliders check boxes and many other graphical metaphors that let the programmer and user tell the computer what to do and how to do it.
Chapter 1.2 System Software
1.2.(a) 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 of 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 you are using an applications package you are not communicating with the computer hardware, you are communicating with the operating system. Without an operating system, no matter how many programs you have, the computer is useless. The operating system sits between the hardware and the application program or user.
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Applications
Package
1.2.b 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. This meant that the expensive part, the computer, was sitting there doing nothing while the human being decided what to do. There are two simple solutions to this problem, one is to buy more machines and the other is to make the machines work more effectively by taking away the slowest part of the system – the human being. Nowadays we might well opt to buy more machines, but this used not to be an option. This problem gave rise to the development of batch processing.
A batch processing operating system is one that does not allow for interaction between the user and the processor during the execution of the work. Lots of programs or data that need to be run are collected together (to form a batch) and they are sent to the computer. The batch operating system then controls their passage through the computer.
Nowadays, batch processing tends to be used where
· there are large amounts of data to be processed,
· the data is very similar in nature and…
· it requires similar processing,
· the computer system has identifiable times when it is not being used, and so has available processor time
· the application does not require human intervention.
Typical examples of applications which would be done using batch processing include production of bank statements from customer files, production of gas (electricity, telephone) bills from customer records, the compilation of high level language programs where a number of users want programs compiled.
Real-time:
A real-time O.S. is one which can react quickly enough to affect the next input, or process to be carried out. Most real-time systems are based on control of some process in the real world or on information handling. A chemical plant has a reaction vessel where the temperature is critical to the result of the process. The temperature is monitored by a computer which accepts input from a sensor and then makes a decision whether to adjust the heating elements in the vessel. In this example, it would not be sensible for the computer to be running any O.S. that is not real-time because if there was a delay in the decision making process, it might mean that the reaction is corrupted in some way. A robot trolley is controlled by a processor which takes input from a sensor following a black line on the floor, and makes decisions concerning steering to keep the trolley on the black line. If the processor was not controlled by a real-time O.S., the trolley would very soon leave the black line because it would not be steering quickly enough. A catalogue shop processes orders by the code for a product being input and the system then comparing the code with information in its files. When it finds the correct code it can report to the user the number of that item that there are in the store. If there was only one left of a certain item, it would be necessary to record the fact that a shopper had bought it before the next shopper has their request dealt with otherwise the second person might be sold the same item. Because the information on the system must be processed immediately the O.S. needs to be ready to handle input as soon as it comes in. This means that it cannot be using up some of its slack time doing other tasks while it is waiting to be asked to do something. This implies that the computer will not be using its full potential as far as processing is concerned. When this happens it is said to display a high rate of redundancy. Real-time systems tend to display a high rate of redundancy.
Single User:
As the term implies, a single user O.S. is specifically one that is used to control a system which has only one user, and their programs, at any one time. A perfect example of a single user system is the one that you may have at home. Only one person uses it at a time. Most single user systems are also multi-tasking.
Multi-tasking:
This is a type of O.S. that allows several applications to be available simultaneously. On a simple single user system you will probably be used to having a number of things running at the same time. Perhaps one window shows a spreadsheet while another shows a word processing application. You may decide to copy the sheet from the spreadsheet software to the word-processed document. It appears that more than one task is running simultaneously. They aren’t, they just appear to be. The O.S. that most of us use on our own computer systems, Windows, is a multi-tasking O.S.
Multi-user:
Again, as the name implies, this type of O.S. services more than one user simultaneously. There are two types of multi-user O.S.:
1. A network system comprises a number of computers linked together for the purposes of communication and sharing of resources. Normally one of the machines is used to control the rest of the system, this machine is called the server. Networks are important because they allow hardware and software to be shared and also mean that a single copy of the information on a system is needed, and so can be kept up to date relatively easily.
2. A time-sharing system has a single (normally powerful) computer which is connected up to a number of terminals. These terminals are not computers as in the case of the network system, but have a very limited amount of processing power. Again, such a system allows communication between users on the system and also allows sharing of hardware and software across the system.
At the moment it is difficult to tell the difference between the two types of multi-user system, but be careful because a network system is not really a multi user system as each computer is only being used by one person at a time. We shall return to this in chapter 3.1
Distributed:
A distributed system is one that allows software and data files to be distributed around a system. An ordinary network will have a server controlling it and the access to the hard drive, which is connected to the server. A distributed system might store the word processing software on one computer’s hard drive, while the files of work are stored somewhere else, and the spreadsheet software is stored on a third disk drive. This can speed access to files because there is no single bottle neck which all the information must pass through, however the security and maintenance of the system are more complicated. Another type of distributed system is to distribute the entire programs and data to more than one place on the network. This speeds up access to the data but means that if data is updated on one part of the system it may not be on others, which means that the different versions of the data need to be compared and amended on a regular basis.
1.2.c Types of User Interface
A computer is used by a person who needs to communicate with the machine in order to instruct it as to their wishes. The person also receives outputs from the computer. The means of communication between the user and the machine is known as the user interface and consists of both hardware and software. 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
· it has specified areas for the data. For example, boxes for input of coded material like the date or the sex of the customer, and areas to be filled in with textual information
· it has a cursor which moves to the next box to be filled in, sometimes the box is highlighted to make it clear to the operator where the data is to be inserted
· some of the boxes are more important than others and the cursor will not move on until some data has been supplied
· it checks that what has been input is sensible for that box before moving on to the next.
Menu based
Menu based interfaces are used in situations where the operator tends not to know what the options are that are available. Examples of this would be information systems for tourists or users of a particular service. A list of choices is made available followed by a further set of choices based on the first choice, and so on until the result is obtained. Imagine a system at a train station in a popular holiday location. The first screen may ask for the general area of interest (accommodation, trips, shopping, entertainment..), once the choice of accommodation has been made the next screen may offer different standards of hotels. The next screen may offer different price bands, and finally a list of all the available properties that match the previous choices.
Input is often done using a touch screen because of the location of such systems and because the people who use them are often in no way computer literate, meaning that simple systems are essential.
Graphical
Graphical interfaces are called GUI (graphical user interface) or WIMP (windows, icons, menus, pointer). The terms describe what the user sees on the screen. There are many different types, but the user would expect to be able to view different applications or files on the screen, this is done by putting each into its own boarded area known as a window. The user will expect to be able to select options by use of menus of choices and by using small pictures which represent the different options available. Choices are selected by the user by using some sort of pointing device to indicate choice, typically this would be a mouse.
Natural language
Sometimes referred to as a conversational interface, the computer will ask questions which elicit a response which gives the user the impression that they are talking to the computer. The trick is that the system restricts itself to questions to which the only sensible answers are the ones that it knows. If the user leaves the expected responses, a message is produced which makes clear that a further attempt is required.
Command line
Or command based interface is one where the user types a series of commands at the keyboard which tell the computer what their intentions are. The user needs to know what the possible commands are, and also needs to understand the way files are stored on the system. The characteristics of a command based interface are
· the user needs to know what commands are available
· the user needs to understand the commands
· the user needs to understand the way that material is stored in the computer system
Because of the above points there are two very important characteristics about a command based interface. First, 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. The second characteristic is that command based interfaces can only be used by computer literate people because you not only have to understand the commands and their uses but you also need to understand something about how the computer operates, particular how information is stored.
There are many other points to be made about interfaces, especially the fact that the second part of the interface consists of the hardware necessary to put the software interface into operation. These points will be made when the appropriate stage is reached in this course.
1.2. (d) Utility software
Utility programs are part of the operating system of a computer and are routines which carry out important tasks which are necessary from time to time on the system. They do not produce a pretty picture, or a letter which can be sent to someone so they are not application programs, but the types of job that they do are so important that the system could not run without them. There are many examples of utility software but we shall limit ourselves to just a few:
1. The surface of a disk can store so much data that the computer cannot handle it all at once so it needs to be split up so that data stored on it can be found again. When it is new a disk surface is blank so the computer “draws lines” on the surface to split it into small areas. The process is called formatting and it is carried out by a utility program called a disk formatter.
2. When files are to be stored on a disk they need to be managed. This includes arranging for them to be stored in a certain place, finding files again after they have been stored, moving them around to get them in a sensible order and deleting them when they are not needed any more. All of these actions are carried out by utility programs called file handlers.
3. A computer system is made up of lots of different sorts of hardware, each piece of which needs instructions about how to work. These programs are called hardware drivers.
4. Some files are very large. In most files it is possible to find simple ways of reducing the size of the file while keeping all its meaning. This can be very important when files are being sent from one computer to another as the communication is speeded up. The programs that reduce the size of files are called file compressors.
5. When files are being sent from one computer to another it is possible that they may contain a virus which will infect the receiving computer. A virus checker (scanner, killer,..) is a utility program which keeps a constant check on files searching for viruses which it will delete if it finds any. www.muktakaryal.blogspot.com via deeprajalevel
Example Questions.
1. Define what is meant by the term operating system. (2)
A. -A (suite of) programs…
-which run the basic functions of the computer/controls the hardware…
-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. Give two reasons why an operating system is likely to be stored on backing storage rather than in the memory of the computer. (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 “…operating system (OS)…” you can then use OS as often as you like in the rest of your answer.
3. Distinguish between a multi-tasking and a multi-access operating system. (2)
A. - A multi-tasking 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. 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)
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. www.muktakaryal.blogspot.com via deeprajalevel
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)
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. 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)
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.
7. State three different types of utility software and explain why they are necessary in a computer system. (6)
A. - Disk Formatter
- to divide up the surface of a disk so that the computer can use it.
- File handling
- to allow the computer to manage files e.g. storing, and finding them.
- Hardware driver
- to give the instructions necessary for using a piece of hardware.
- File compressor
- to reduce the size of files so that transmission can be done faster.
- Virus checker
- to find and delete viruses on a system before they can damage files.
Note. Lots of answers here, but they are all from the syllabus, none are made up because there is no doubt about these whereas there may be doubts if you do not stick to the accepted ones.
No proprietary brand names are used. Scandisk and Winzip are brand names and will not get the marks.
Be careful about giving different types – file storage, file sorting and file deletion are all utility programs but they are all file handlers, so would only get one pair of marks.
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