Q. 41 Explain the following terms.
Q. 42 What is GUI ? State any four advantages of GUI
Q. 43 What is GUI ? Explain in brief any two features of GUI.
Q. 44 What is meant by GUI ? What are the essential components of GUI ? Explain any three.
Q. 45 Explain in short the function of Menubar and scroll bar components of G.U.I
Q. 46 Explain various controls of G.U.I.
Q. 41 Explain the following terms.
Ans: (1) Locality of reference :
i) The basic principle behind virtual memory is called locality of reference.
ii) This gives some basis to forecast whether a page is likely to be referenced in the near
future or not, depending on its behavior in past.
iii) Thus, it helps to decide whether the page should be thrown out from main memory
to make space for new page or not. )
iv) If this principle is not valid, user can not throw any pages out on the disk from
memory without a possible severe degradation in the performance.
(2) Page fault :
i) In many systems, when a process is executing with only a few pages in memory and
when an instruction is encountered which refers to any instruction or data in some
other page which is outside the main memory i.e. on the disk,la ‘page fault’ occurs.
ii) At this stage, the operating system must bring the required page into the memory
before the execution of that instruction can restart.
(3) Working set :
i) At any time, a process has a number of pages in the physical memory. Not all of these are actively referred.
ii) The set of pages in the physical memory actively referred to at any moment is called working set.
iii) This has a significant bearing on the policy of bringing in pages from the disk to the
main memory, if the operating system follows the “Working set model.”
4) Page replacement policy :
i) As the number of processes and the number of pages in the main memory increase all
the page frames become occupied.
ii) At this time, if a new page is to be brought in, the operating systern has to overwrite some existing page in the memory
iii) The page To be overwritten is selec ted by page replacement policy.
iv) There are a number of ways in which the O.S. selects the page to be overwritten. The
0S, designer chooses one amongst many of such policies and writes corresponding algorithm for it,
(5) Dirty page / Dirty bit
i) The page which is modified after it is loaded in main memory from disk is called as
dirty page
ii) The operating system maintains one bit for each physical page frame to denote whether
a page has become dirty or not. This bit is called dirty bit.
6) Demand paging :
i) In demand paging, a page is brought in only when demanded.
ii) Consider a process is created with no pages in main memory. When the process is dispatched initially, the program counter will have been loaded with the address of first instruction. This address obviously belongs to a page outside the main memory. So a page fault will occur and the O.S. will now bring that page in memory.
iii) In this way as page fault goes on occurring, the O.S. brings new referred pages. This
is called demand paging.
iv) The drawback of demand paging is that a lot of pages which have been used in past,
but which now are not required, remain in memory unnecessarily.
GUI – Graphical User Interface
Q. 42 What is GUI ? State any four advantages of GUI
Ans. : GUI : The interface which replaces cryptic commands by their graphical representation are called Graphical User Interface (GUI).
Windows operating system is GUI based operating system.
Advantages of GUI :
1) With GUI commands are replaced by graphics. Hence it is not necessary to remember the
command and its meaning,
2) With GUI user can run several programs simultaneously.
3) User can communicate and exchange data between programs without transferring or copying
files.
4) Easy to use, consistent GUI for virtually all programs.
Q. 43 What is GUI ? Explain in brief any two features of GUI.
Ans. : GUI: The interface which replace cryptic commands by their graphical representation are called Graphical User Interface (GUI).
Windows operating system is GUI based operating system.
Features of GUI:
1) Replacement of command with icons :
(a) Commands are grouped together in various levels of hierarchy and when the user selects a group, further commands in that group are displayed.
(b) This allows the user to select a command using a cursor and simply clicking on it.
(c) User can select the command and use the application without first having to know about the computer and its working.
(d) The display of these command sequences takes place graphically.
2) Provide on-line HELP :
(a) GUI – based applications provide “HELP” about various features of the application.
(b) HELP can assist the user in knowing everything about the application.
(c) In the windowing environment, if user gets confused at any point, a HELP is readily
available. This makes GUI-based applications more popular and efficient.
Q. 44 What is meant by GUI ? What are the essential components of GUI ? Explain any three.
Ans. : GUI : The interface which replace cryptic commands by their graphical representation are called Graphical User Interface (GUI).
Windows operating system is GUI based operating system.
Essential components of GUI are :
(1) Menu bar
(2) Scroll bar
(3) Controls push button, option button, radio button, check box, list box, Entry box,
Combo box)
(4) Dialogue boxes
(5) Feedback pointer
1) Menu bar:
(i) Menu bar normally appears at the top of the window under the window title.
(ii) Some commonly used menu bar options are File, Edit, View, Help etc.
(iii) When one of these menu is selected, a pulldown menu appears on the screen.
2) Scroll bar:
(i)Scroll bars allow user to scroll window horizontally and vertically.
(i) Scroll bars are generally used to look at information, which is not currently visible in screen, by scrolling window horizontally or vertically.
(iii) A scroll bar consists of a horizontal or vertical scroll area with a slider box and an arrow in a box at each end.
(vi) Slider box gives a hint on size and position of the visible part of object.
3) Dialogue boxes :
(i) Dialogue box is a window, used by the application to interact with the user.
(ii) A dialogue box can also be used to display information or to get user input and also
for a combination of these two functions.
(iii) Dialogue boxes are of two types :
(a) Modal dialogue box
(b) Modeless dialogue box.
(iv) A dialogue box where an application can continue only after the user has responded to the dialogue is called modal dialogue box.
(v) A dialogue box, which allows user to continue without responding to it is called modeless dialogue box.
Q. 45 Explain in short the function of Menubar and scroll bar components of G.U.I
Ans :
(i) Menubar :
i) A menubar consists of different main menus, which can be used in program.
ii) The main menus consists of different submenus. A menu can be selected by clicking it.
iii) A menubar is normally present at the top of the window under the window title.Some of the commonly used menu options are File, Edit, Help etc.
iv)When one of these menu is selected by clicking, a pull down menu list appears on the screen.
v) A pull down menu is a rectangular box, with more specific action listed in the box, out of which one can be selected by clicking a particular menu item.
(ii) Scroll bars :
i) Scroll bars allow user to scroll window horizontally and vertically.
ii) Scroll bars are generally used to look at information, which is not currently visible in screen, by scrolling window horizontally or vertically.
iii) A scroll bar consists of a horizontal or vertical scroll area with a slider box and an
arrow in a box at each end.
iv) Slider box gives a hint on size and position of the visible part of object.
Q. 46 Explain various controls of G.U.I.
Ans. A varity of controls are used in a GUL to enable user to select type of information or to select specific operation to be carried out. That are either buttons or boxes. Some of the control buttons are :
1) Push button :
It is a rectangular button having a label, indicating action to be carried out. This button is used to select an action represented by button. This button normally used when one action is to be selected at of many choices.
For e.g. [SAVE]
2) Option button or radio buttons :
It consists of a graphical image, which is used to select one object out of several possible objects. The currently selected can be distinguished from the others by highlighting on the graphic image :
e.g.
- Workarea
- Modeless
- Apllication
3) Check buttons :
A check button consists of a square box and an accompanying text. This is used for selecting one or more choices from a list of options.
e.g.
☑️ Auto manage
☑️ Default position
☑️ Align
4)The Box controls are list box and entry box :
(i) List box :
A list box is a rectangular box with scroll bars. This allows user to select one item from a scrollable list of choices.
(ii) Entry box :
Entry box is a rectangular box, which allows user to enter some text. An additional hint about the type of text to be entered is provided near the box.
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