OPERATING SYSTEM IMPORTANT QUESTION ANSWER Part 9

OPERATING SYSTEM IMPORTANT QUESTION ANSWER PART 9

for IGNOU BCA MCA Students

16) What necessary conditions can lead to a deadlock situation in a system?

Deadlock situations occur when four conditions occur simultaneously in a system: Mutual exclusion; Hold and Wait; No preemption; and Circular wait.

17) Enumerate the different RAID levels.

RAID 0 – Non-redundant striping

RAID 1 – Mirrored Disks

RAID 2 – Memory-style error-correcting codes

RAID 3 – Bit-interleaved Parity

RAID 4 – Block-interleaved Parity

RAID 5 – Block-interleaved distributed Parity

RAID 6 – P+Q Redundancy

18) Describe Banker's algorithm

Banker's algorithm is one form of deadlock-avoidance in a system. It gets its name from a         banking system wherein the bank never allocates available cash in such a way that it can no longer satisfy the needs of all of its customers.

19) What factors determine whether a detection-algorithm must be utilized in a deadlock avoidance system?

One is that it depends on how often a deadlock is likely to occur under the implementation of this algorithm. The other has to do with how many processes will be affected by deadlock when this algorithm is applied.

20) Differentiate logical from physical address space.

Logical address refers to the address that is generated by the CPU. On the other hand, physical address refers to the address that is seen by the memory unit.

21) How does dynamic loading aid in better memory space utilization?

With dynamic loading, a routine is not loaded until it is called. This method is especially useful when large amounts of code are needed in order to handle infrequently occurring cases such as error routines.

22) What are overlays?

Overlays are used to enable a process to be larger than the amount of memory allocated to it. The basic idea of this is that only instructions and data that are needed at any given time are kept in memory.

23) What is the basic function of paging?

Paging is a memory management scheme that permits the physical-address space of a process to be noncontiguous. It avoids the considerable problem of having to fit varied sized memory chunks onto the backing store.

24) What is fragmentation?

Fragmentation is memory wasted. It can be internal if we are dealing with systems that have fixed-sized allocation units, or external if we are dealing with systems that have variable-sized allocation units.

25) How does swapping result in better memory management?

During regular intervals that are set by the operating system, processes can be copied from main memory to a backing store, and then copied back later. Swapping allows more processes to be run that can fit into memory at one time.

26) Give an example of a Process State.

- New State – means a process is being created

- Running – means instructions are being executed

- Waiting – means a process is waiting for certain conditions or events to occur

- Ready – means a process is waiting for an instruction from the main processor

- Terminate – means a process is done executing

27) What is a socket?

A socket provides a connection between two applications. Each endpoint of a communication is a socket.

28) What is Direct Access Method?

Direct Access method is based on a disk model of a file, such that it is viewed as a numbered sequence of blocks or records. It allows arbitrary blocks to be read or written. Direct access is advantageous when accessing large amounts of information.

29) When does trashing occur?

Trashing refers to an instance of high paging activity. This happens when it is spending more

time paging instead of executing.