Operating System Past Year Answer
JUNE 2012
PART A
QUESTION 6
Based on Figure 1 below, describe the responsibilities of the resource manager. (5M)
The general form of a resource manager
Figure 1 * As an Internal resource name is an internal name for the resource used by the operating system code. * As total unit are a number of resource units configured into the system. * Available unit is a number of units currently available. * List of available units is a set of available units of this resource type that are available for use by processes. * List of blocked processes is a list of processes that have a pending request for units of this resource type.
QUESTION 7
Pipes are a very simple model introduced by UNIX for accomplishing interprocess communication (IPC). a) Define IPC. (2M)
Inter-process communication (IPC) is a set of methods for the exchange of data among multiple threads in one or more processes.
b) Explain how pipes are used to accomplish IPC. (3M)
Piping is a process where the output of one process is made the input of another.
PART B
QUESTION 2
c) Assume that the list of holes in a variable partitions memory system contains the following entries (in the given order): 400K, 150K, 270K and 500K. Consider the following sequence of requests :
A = 450K, B = 200K, C = 50K and D = 300K.
d) Draw the block of memory diagram using First Fit strategy to show the placement of the block requested. (4M)
450 K
50 K
200 K
50 K
270 K
100 K
200 K
500 K
270 K
150 K
400 K
Balance
Block Size
ii) What is the total size of internal fragmentation? (1M)
200K + 100K + 50K = 350K
iii) What is the total size of the external fragmentation? (1M)
200K + 100K + 50K + 270K = 620K
iv) Distinguish between internal fragmentation and external fragmentation. (4M)
External Fragmentation | Internal Fragmentation | * Occurs when the first free block of memory is insufficient for the next program to use. * It is dynamic memory allocation
PART A
QUESTION 6
Based on Figure 1 below, describe the responsibilities of the resource manager. (5M)
The general form of a resource manager
Figure 1 * As an Internal resource name is an internal name for the resource used by the operating system code. * As total unit are a number of resource units configured into the system. * Available unit is a number of units currently available. * List of available units is a set of available units of this resource type that are available for use by processes. * List of blocked processes is a list of processes that have a pending request for units of this resource type.
QUESTION 7
Pipes are a very simple model introduced by UNIX for accomplishing interprocess communication (IPC). a) Define IPC. (2M)
Inter-process communication (IPC) is a set of methods for the exchange of data among multiple threads in one or more processes.
b) Explain how pipes are used to accomplish IPC. (3M)
Piping is a process where the output of one process is made the input of another.
PART B
QUESTION 2
c) Assume that the list of holes in a variable partitions memory system contains the following entries (in the given order): 400K, 150K, 270K and 500K. Consider the following sequence of requests :
A = 450K, B = 200K, C = 50K and D = 300K.
d) Draw the block of memory diagram using First Fit strategy to show the placement of the block requested. (4M)
450 K
50 K
200 K
50 K
270 K
100 K
200 K
500 K
270 K
150 K
400 K
Balance
Block Size
ii) What is the total size of internal fragmentation? (1M)
200K + 100K + 50K = 350K
iii) What is the total size of the external fragmentation? (1M)
200K + 100K + 50K + 270K = 620K
iv) Distinguish between internal fragmentation and external fragmentation. (4M)
External Fragmentation | Internal Fragmentation | * Occurs when the first free block of memory is insufficient for the next program to use. * It is dynamic memory allocation