Mobile Operating Systems Symbian The Symbian OS home page shows the demand paging. http:// www.symbian.com/symbianos/index.html Developer pages. http://www.forum.nokia.com/info/sw.nokia.com/id/dbb8841d- 832c-43a6-be13- f78119a2b4cb.html Android. Open Handset Alliance --- Android Google mobile OS based on Linux. http:// code.google.com /android/ SW stack http://code.google.com/android/what-is-android.html SDK tools http://code.google.com/android/intro/hello-android.html Hardware -- Paging Paging System for Pentium - - 4K pages and 4Mpages http://www.rcollins.org/ddj/May96/
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Mobile Operating SystemsSymbian
The Symbian OS home page shows the demand paging.http://www.symbian.com/symbianos/index.html
• Access control• File System Mounting• Allocation methods
– Contiguous– Linked– indexed
• Real file systems– FAT– UFS– NTFS
Files
• A file is a named collection of related information that is recorded on secondary storage.– It is the smallest logical storage unit.
• Data to be stored has to be in a file
– It has a certain defined structure, which depends on its type.
• Text files, source files, executable files, object files, etc.
File attributes
• File attributes typically include– Name -- human readable name– Identifier -- non-human-readable name– Type -- is need for those systems that supports
different types of files– Location -- a pointer to the location– Size -- the current size– Protection -- access control information– Time, date, and user identification.
• They are kept in the directory structure.
File Operations
• A file is an abstract data type and is associated with operations.– Basic operations
• Creating a file• Writing a file• Reading a file• Repositioning within a file• Deleting a file• Truncating a file
– Other two common operations• Appending to a file• Renaming a file
• Access control• File System Mounting• Allocation methods
– Contiguous– Linked– indexed
• Real file systems– FAT– UFS– NTFS
Exam
• 5 questions,:-
• Compulsory :• 1 mixed (MJWM, MWD, IMC)
• Choice (2 of 4):• 2 Computer Arch (MJWM)• 1 Networks (MWD)• 1 Operating Systems (IMC)
• Maximum mark obtainable 75
Exam
• What is …. [2]
• State …. [1]
• Briefly describe … . [2]
• Explain …. [5]
• Describe …. [6]
(a) CPU scheduling algorithms are designed to keep a computer system running efficiently in a multiprogramming environment. Probably the best known criterion for judging the success of a particular scheduling algorithm is to measure the CPU utilization, i.e. the percentage of time that the CPU is busy (i.e. not sitting idle). Briefly describe three other criteria that could be used to measure the efficiency of CPU scheduling algorithms.
[6]
(b) Outline a scheduling algorithm that you think would be particularly appropriate for maximizing CPU utilization. Why do you consider it to be suitable? Describe scheduling algorithms that you believe would be suited to multiprogramming environments with efficiency measures based on each of the three other criteria from part (a). [8]
Past Questions
Past Question• (c) Describe the meaning of the term virtual memory? Briefly distinguish
between paging and segmentation, as memory management schemes for computer systems [4]
• (d) Describe the main advantages and disadvantages of using segmentation rather than paging. [3]
• (e) Consider a computer memory management system in which memory contains the following hole sizes in memory order: 10 KB, 4 KB, 20 KB, 18 KB, 7 KB, 9 KB, 12 KB and 15 KB. Which hole is taken for successive segment requests of: 12 KB, 10 KB, 9 KB when each of the following algorithms is used:-
• (i) first fit, [1]• (ii) best fit, [1]• (iii) worst fit and [1]• (iv) next fit. [1]