CS604 Final Term Subjective with References by Faisal

 MUHAMMAD FAISAL  · MIT 4th Semester · Al-Barq Campus (VGJW01) Gujranwala · Reference Short Questions for Final TERM EXAMS · CS604 – OPERATING SYSTEM

Q.No.1 Scan Algorithm is sometimes called the elevator algorithm, why? (Page#244)

The Scan algorithm is sometimes called the elevator algorithm, since the disk arm behaves like an elevator in a building servicing all the requests (people at floors), going up and then reversing to service the requests going down.

Q.No.2 What is basic logic in FIFO page replacement algorithm? (Page#199)

The simplest page-replacement algorithm is a FIFO algorithm. A FIFO replacement algorithm associates with each page the time when that page was brought into memory. When a page must be replaced, the oldest page is chosen.

Q.No.3 What is mounting? Name two types of mounting. Give your answer

with respect to File System? (Page#226)

file system is mounted and accessed. You can mount a file or directory if you have access to the file or directory being mounted and write permission for the mount point

These are the types of mounts:

1. Remote mount
2. Local mount

Q.No.4 Write three main characteristics memory management System? (Page#151)

1. The purpose of memory management is to ensure fair, secure, orderly, and efficient use of memory.
2. The task of memory management includes keeping track of used and free memory space, as well as when, where, and how much memory to allocate and de-allocate.
3. It is also responsible for swapping processes in and out of main memory.

Q.No.5 Summarize the tradeoffs among simple arrays, trees, and hash tables

as implementations of a page table. (Page#173,186)

Arrays: Arrays, lists and tables are often allocated more memory than they actually need. An array may be declared 100 by 100 elements even though it is seldom larger than 10 by 10 elements.

Hash Tables: This is a common approach to handle address spaces larger then 32 bits .Usually open hashing is used. Each entry in the linked list has three fields: page number, frame number for the page, and pointer to the next element

Q.No.6 How to implement hold and wait which can ensure that a deadlock

will not occur? (Page#129)

A process must be holding at least one resource and waiting to acquire additional resources that are currently being held by other processes.

Q.No.7 List down 2 major benefits of virtual memory (Page#186)

1. Virtual Memory is the separation of user logical memory from physical memory. This separation allows an extremely large virtual memory to be provided for programmers when only a smaller physical memory is available.
2. Virtual memory makes the task of programming easier because the programmer need not worry about the amount of physical memory.

Q.No.8 What are the possible system for the input redirection in the

UNIX/LINX system (Page#55)

Linux redirection features can be used to detach the default files from stdin, stdout, and stderr and attach other files with them for a single execution of a command. The act of detaching defaults files from stdin, stdout, and stderr and attaching other files with them is known as input, output, and error redirection.

Here is the syntax for input redirection:

command < input-file or command 0< input-file

Q.No.9 What is the purpose of “stub” in dynamic linking, give answer with respect to memory? (Page#155)

Answer: With dynamic linking, a stub is included in the image for each library-routine reference. This stub is a small piece of code that indicates how to locate the appropriate memoryresident library routine or how to load the library if the routine is not already present. During execution of a process, stub is replaced by the address of the relevant library code and the code is executed .If library code is not in memory, it is loaded at this time.