Tag Archive: OS


This space can be utilized for clearing doubts on the concepts of Advanced Operating System PECS 3409 of BPUT Syllabus. Questions will be added to the topic body and answers will be discussed in the comments.

  1. What is consistency maintenance in distributed system and what are its prime categories?
  2. Discuss the technique by which RPCs can be replaced in threaded environment for increasing performance?
  3. What is Omega Network?
  4. Draw 16 input Omega network
    16OmegaNetwork

    16 input Omega Network

     

See this document for other Answers :

Q h 7thECE2006

A logical address space of 12 pages of 1024 bytes each mapped to a physical memory of 64 frames. What would be the minimum number of bits in logical address?

Q i 7thECE2006

What would be the minimum number of bits in physical address?

Q 2 7thECE2006

A demand paged virtual system has the following parameters

  1. Time to serve page faults:
    • When a new frame is allocated: 12 mili seconds
    • When a modified page is replaced: 20 mili seconds
  2. Memory access time: 200 nano seconds
  3. While serving a page fault:
    • Probability of allocating a new frame: 30%
    • Probability of allocating a modified frame: 70%

Find the maximum page fault rate such that degradation in memory access time is not more than 20%.

The Embedded Battle

Today the PECS 3405 EMBEDDED SYSTEMS paper was over.
Most of the short questions were good; albeit some difficulties in the
longer siblings.


  1. Shorts
    1. List down various hardware and software resources in an embedded computer system.
    2. Why the response time of LINUX is lower that WINDOWS operating system? <<Grammatical Error
    3. What are the parameters used to characterize a real time task?
    4. The performance of hierarchical memory system is faster. Why?
    5. Why embedded systems are realized as real time systems?
    6. Distinguish between hard, soft and firm real time systems?
    7. Distinguish between periodic, aperiodic and sporadic tasks in a RTOS.
    8. List down at least three tools that support the design and development of embedded system.
    9. What do you mean by release time and response time of real-time tasks?
    10. List down various hardware and software drivers used in an embedded system.
  2. Long
    1. Explain the relationship between operating system, computer hardware, system software in an embedded system with the help of a schematic diagram. [4]
    2. What is a system call? Explain the uses of system call in embedded system with an example. [4]
    3. The system calls are implemented as interrupt service routines. Justify. [2]
  3. Long
    1. What do you mean by interface synthesis? Illustrate how the communication time requirements are estimated using process-resource mapping and architectural inputs. [4]
    2. Describe a set of native communication application program interfaces in JAVA for the communication between JAVA and the system-on-chip. [6]
  4. Long
    1. What are various criteria to be considered for processor scheduling in an embedded system? Explain various types of processor scheduling policies with examples. Which of these is followed in LINUX operating system. [5]
    2. Five batch jobs A through E, arrive at a computer center at almost the same time. They have estimated running time of 10, 6, 2, 4 and 8 minutes. Their (externally determined) priorities are 3, 5, 2, 1 and 4 respectively, with 5 being the highest priority. For each of the following algorithms determine the mean process turn-around time, ignore process switching overhead: [5]
      1. Round Robin – assume that the system is multi-programmed and that each job gets its fair share of CPU.
      2. Priority Scheduling – assume that only one job at a time runs, until it finishes. All jobs are completely CPU bound.
      3. First come, first served (run in order 10, 6, 2, 4, 8 ) – ditto –
      4. Shortest job first – ditto –
  5. Long
    1. Discuss the role of tools for the development and debugging of embedded systems. What do you mean by run-control debugging and field debugging. [4]
    2. How does the response time is affected by enabling/disabling interrupts in every kernel service call in a real-time operating system? [3]
    3. Discuss the types of interrupts in embedded C. [3]
  6. Long
    1. A virtual memory system has an address space of 8k words, a memory space of 4k words and page and block sizes of 1k words. The following page reference changes occur during a given time interval. (Only page changes are listed, if the same page is referenced again, it is not listed twice). 4 2 0 1 2 6 1 4 0 1 0 2 3 5 7 Determine the four pages that are resident in main memory after each page reference change if the replacement algorithm used is (i)FIFO (ii)LRU. [5]
    2. Disk requests come into the disk driver for cylinders 10, 22, 20, 2, 40, 6 and 38 in that order. A seek takes 6 msec per cylinder moved. How much seek time is needed for (i) First come, first served, (ii) Closest cylinder next, and (iii) Elevator algorithm (initially moving upward). In all cases the arm is initially at cylinder 20. State advantages and disadvantages for each methods. [5]
  7. Long
    1. Explain briefly different real time operating systems with examples. [4]
    2. What is the primary goal of a real-time operating system? [2]
    3. Why round-robin scheduling policy is appropriate for time-sharing operating systems? Explain with example. [4]
  8. Long
    1. Explain the interprocess communication mechanisms in LINUX. [4]
    2. Discuss the message-based interprocess communication in embedded real-time systems and its appropriate operating system support. [3]
    3. How an optimized communication mechanism can be obtained using message-based interprocess communication. [3]

What do you think?

Yesterday at-least four of my students rang me up for their doubts. It is not unnatural but the stride of their studies are quite disturbing. Approximately after 10 classes from start of the semester, they got themselves indulged in the placement spree. Nevertheless, classes were missed. They made it a custom to miss the day previous to the placement day albeit for preparations; the d’ day for competition and the following day to take rest.

Not to overemphasize, they lost oodles of classes. Now as BPUT started to hammer their heads with the exam time table, they are realizing now what has passed out!

If this much would have been the story then it would have been fine. Still to come; the shock!

A couple of days back I took an abandoned class in the pack-slotted extra classes schedule. To my horror, only a few students were there. From the list of the absentees were many notable faces:-

The CEO of PriyaZeem Productions, The specific students who had handed me problems to solve, regular absentees … -Oh my God! with approx ~10 students I started the discussion.

If they miss regular classes, drop extra classes, whack the class test, what is in store is only a matter of plain guess!

May God Help Them. (Tathastu, Amen, Zumma-ameen)