Monday 17 September 2012

OS Interview Questions-2



1.Define MULTICS?
Ans: MULTICS (Multiplexed information and computing services) operating system was developed from 1965-1970 at Massachusetts institute of technology as a computing utility. Many of the ideas used in MULTICS were subsequently used in UNIX.

2.What is SCSI?
Ans: Small computer systems interface.

3.What is a sector?
Ans: Smallest addressable portion of a disk.

4.What is cache-coherency?
Ans: In a multiprocessor system there exist several caches each may containing a copy of same variable A. Then a change in one cache should immediately be reflected in all other caches this process of maintaining the same value of a data in all the caches s called cache-coherency.

5.What are residence monitors?
Ans: Early operating systems were called residence monitors.

6.What is dual-mode operation?
Ans: In order to protect the operating systems and the system programs from the malfunctioning programs the two mode operations were evolved:
1. System mode.
2. User mode.
Here the user programs cannot directly interact with the system resources, instead they request the operating system which checks the request and does the required task for the user programs-DOS was written for / intel 8088 and has no dual-mode. Pentium provides dual-mode operation.

7.What are the operating system components?
Ans:
1. Process management
2. Main memory management
3. File management
4. I/O system management
5. Secondary storage management
6. Networking
7. Protection system
8. Command interpreter system

8.What are operating system services?
Ans:
1. Program execution
2. I/O operations
3. File system manipulation
4. Communication
5. Error detection
6. Resource allocation
7. Accounting
8. Protection

9.What are system calls?
Ans: System calls provide the interface between a process and the operating system. System calls for modern Microsoft windows platforms are part of the win32 API, which is available for all the compilers written for Microsoft windows.

10.What is a layered approach and what is its advantage?
Ans: Layered approach is a step towards modularizing of the system, in which the operating system is broken up into a number of layers (or levels), each built on top of lower layer. The bottom layer is the hard ware and the top most is the user interface.The main advantage of the layered approach is modularity. The layers are selected such that each uses the functions (operations) and services of only lower layer. This approach simplifies the debugging and system verification.

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