COS3721 Long Questions And Verified Detailed Answers!!
Explain why an operating system can be viewed as a resource allocator. - ANSWER A
computer system contains many resources that may be required to solve a problem:
CPU time, memory space, file-storage space, I/O devices, and so on. The operating
system acts as the manager of these resources. It must decide, out of many, possibly
conflicting requests, how resources are allocated to particular programs and users, so
that it can operate the computer system efficiently and fairly.
Explain the purpose of an interrupt vector - ANSWER The interrupt vector is simply a
table of pointers to specific interrupt-handling routines. Since there is a finite number of
interrupts, this table then provides much greater efficiency in the processing of the
interrupts rather than having a general-purpose, interrupt-processing routine.
What is a bootstrap program, and where is it stored? - ANSWER A bootstrap program is
the first program that runs on the computer when it is powered up or rebooted. It
initializes everything in the system, from CPU registers to device controllers to contents
of main memory. It is normally stored in read-only memory (ROM) or electrically
erasable programmable read-only memory (EEPROM), referred to as firmware, in the
computer hardware.
What is the function of device controllers and device drivers in a computer? - ANSWER
A general-purpose computer system contains one or more CPUs and multiple device
controllers connected through a common bus. Each device controller controls one or
more peripheral devices of a particular type. The device controller transfers data
between the peripheral devices under its control and its own local buffer storage.
Typically, operating systems have a device driver for each device controller. This device
driver understands the device controller and presents a uniform interface for the device
to the rest of the operating system.
Why are clustered systems considered to provide high-availability service? - ANSWER
Clustered systems are considered high-availability in that these types of systems have
redundancies capable of taking over a specific process or task in the case of a failure.
The redundancies are inherent due to the fact that clustered systems are composed of
, two or more individual systems coupled together.
Describe the differences between physical, virtual, and logical memory. - ANSWER
Physical memory is the memory available to machines for execution, while virtual
memory is a method of program execution that, by using disk memory as the backing
store for main memory, can be larger than the amount of physical memory present.
Logical memory is an abstraction of the different types of memory of the computer that
provides a simplified view of memory for programmers and applications and frees them
from concern over memory-storage limitations
Describe the two modes of operation of an operating system. - ANSWER To ensure
proper execution of the operating system, most computer systems provide hardware
support to differentiate between user mode and kernel mode. A mode bit is added to the
hardware of the computer that indicates the current mode: kernel 0 or user 1. When a
computer system is running on behalf of an application, then the system is said to be in
the user mode. When an application invokes a request for some service from the
operating system, by means of a system call, it has to switch to the kernel mode to fulfill
that request.
Explain cache coherency. - ANSWER In a multiprocessor environment, the same data
could exist in the local cache of every CPU. Each time any CPU modifies that data, a
different CPU is supposed to see a fresh version of it. Cache coherence simply means
having several caches store an up-to-date copy of stored data.
Why is main memory not suitable for permanent program storage or backup purposes?
What is the major disadvantage to storing information on a magnetic disk drive as
opposed to main memory? - ANSWER Main memory is a volatile memory in that any
power loss to the system will result in erasure of the data stored within that memory.
While disk drives can store more information permanently than main memory, disk
drives are considerably slower.
Describe the compute-server and file-server types of server systems. - ANSWER The
compute-server system provides an interface to which a client can send a request to
perform an action-for example, read data from a database; in response, the server
executes the action and sends back results to the client. The file-server system provides
a file-system interface where clients can create, update, read, and delete files. A
familiar example is a Web server delivering files to Web browsers operating on client
machines
Explain why an operating system can be viewed as a resource allocator. - ANSWER A
computer system contains many resources that may be required to solve a problem:
CPU time, memory space, file-storage space, I/O devices, and so on. The operating
system acts as the manager of these resources. It must decide, out of many, possibly
conflicting requests, how resources are allocated to particular programs and users, so
that it can operate the computer system efficiently and fairly.
Explain the purpose of an interrupt vector - ANSWER The interrupt vector is simply a
table of pointers to specific interrupt-handling routines. Since there is a finite number of
interrupts, this table then provides much greater efficiency in the processing of the
interrupts rather than having a general-purpose, interrupt-processing routine.
What is a bootstrap program, and where is it stored? - ANSWER A bootstrap program is
the first program that runs on the computer when it is powered up or rebooted. It
initializes everything in the system, from CPU registers to device controllers to contents
of main memory. It is normally stored in read-only memory (ROM) or electrically
erasable programmable read-only memory (EEPROM), referred to as firmware, in the
computer hardware.
What is the function of device controllers and device drivers in a computer? - ANSWER
A general-purpose computer system contains one or more CPUs and multiple device
controllers connected through a common bus. Each device controller controls one or
more peripheral devices of a particular type. The device controller transfers data
between the peripheral devices under its control and its own local buffer storage.
Typically, operating systems have a device driver for each device controller. This device
driver understands the device controller and presents a uniform interface for the device
to the rest of the operating system.
Why are clustered systems considered to provide high-availability service? - ANSWER
Clustered systems are considered high-availability in that these types of systems have
redundancies capable of taking over a specific process or task in the case of a failure.
The redundancies are inherent due to the fact that clustered systems are composed of
, two or more individual systems coupled together.
Describe the differences between physical, virtual, and logical memory. - ANSWER
Physical memory is the memory available to machines for execution, while virtual
memory is a method of program execution that, by using disk memory as the backing
store for main memory, can be larger than the amount of physical memory present.
Logical memory is an abstraction of the different types of memory of the computer that
provides a simplified view of memory for programmers and applications and frees them
from concern over memory-storage limitations
Describe the two modes of operation of an operating system. - ANSWER To ensure
proper execution of the operating system, most computer systems provide hardware
support to differentiate between user mode and kernel mode. A mode bit is added to the
hardware of the computer that indicates the current mode: kernel 0 or user 1. When a
computer system is running on behalf of an application, then the system is said to be in
the user mode. When an application invokes a request for some service from the
operating system, by means of a system call, it has to switch to the kernel mode to fulfill
that request.
Explain cache coherency. - ANSWER In a multiprocessor environment, the same data
could exist in the local cache of every CPU. Each time any CPU modifies that data, a
different CPU is supposed to see a fresh version of it. Cache coherence simply means
having several caches store an up-to-date copy of stored data.
Why is main memory not suitable for permanent program storage or backup purposes?
What is the major disadvantage to storing information on a magnetic disk drive as
opposed to main memory? - ANSWER Main memory is a volatile memory in that any
power loss to the system will result in erasure of the data stored within that memory.
While disk drives can store more information permanently than main memory, disk
drives are considerably slower.
Describe the compute-server and file-server types of server systems. - ANSWER The
compute-server system provides an interface to which a client can send a request to
perform an action-for example, read data from a database; in response, the server
executes the action and sends back results to the client. The file-server system provides
a file-system interface where clients can create, update, read, and delete files. A
familiar example is a Web server delivering files to Web browsers operating on client
machines
