Operating System Interview Questions and Answers
What's OPERATING SYSTEM?
An Operating System, or OS, is a software program that
enables the computer hardware to communicate and operate
with the computer software. Without a computer Operating
System, a computer would be useless.
OPERATING SYSTEM TYPES
As computers have progressed and developed so have the
types of operating systems. Below is a basic list of the
different types of operating systems and a few examples
of Operating Systems that fall into each of the
categories. Many computer Operating Systems will fall
into more than one of the below categories.
GUI - Short for Graphical User Interface, a GUI
Operating System contains graphics and icons and is
commonly navigated by using a computer mouse. See our
GUI dictionary definition for a complete definition.
Below are some examples of GUI Operating Systems.
Multi-user - A multi-user Operating System allows
for multiple users to use the same computer at the same
time and/or different times. See our multi-user
dictionary definition for a complete definition for a
complete definition. Below are some examples of
multi-user Operating Systems.
Mac OS X
Multiprocessing - An Operating System capable of
supporting and utilizing more than one computer
processor. Below are some examples of multiprocessing
Mac OS X
Multitasking - An Operating system that is
capable of allowing multiple software processes to run
at the same time. Below are some examples of
multitasking Operating Systems.
Mac OS X
Multithreading - Operating systems that allow
different parts of a software program to run
concurrently. Operating systems that would fall into
this category are:
Mac OS X
What are the basic functions of an operating system?
- Operating system controls and coordinates the use of
the hardware among the various applications programs for
various uses. Operating system acts as resource
allocator and manager. Since there are many possibly
conflicting requests for resources the operating system
must decide which requests are allocated resources to
operating the computer system efficiently and fairly.
Also operating system is control program which controls
the user programs to prevent errors and improper use of
the computer. It is especially concerned with the
operation and control of I/O devices.
Why paging is used?
-Paging is solution to external fragmentation problem
which is to permit the logical address space of a
process to be noncontiguous, thus allowing a process to
be allocating physical memory wherever the latter is
While running DOS on a PC, which command would be used
to duplicate the entire diskette?
What resources are used when a thread created? How do
they differ from those when a process is created?
When a thread is created the threads does not require
any new resources to execute the thread shares the
resources like memory of the process to which they
belong to. The benefit of code sharing is that it allows
an application to have several different threads of
activity all within the same address space. Whereas if a
new process creation is very heavyweight because it
always requires new address space to be created and even
if they share the memory then the inter process
communication is expensive when compared to the
communication between the threads.
What is virtual memory?
Virtual memory is hardware technique where the system
appears to have more memory that it actually does. This
is done by time-sharing, the physical memory and storage
parts of the memory one disk when they are not actively
What is Throughput, Turnaround time, waiting time and
Throughput – number of processes that complete their
execution per time unit. Turnaround time – amount of
time to execute a particular process. Waiting time –
amount of time a process has been waiting in the ready
queue. Response time – amount of time it takes from when
a request was submitted until the first response is
produced, not output (for time-sharing environment).
What is the state of the processor, when a process is
waiting for some event to occur?
What is the important aspect of a real-time system or
Mission Critical Systems?
A real time operating system has well defined fixed
time constraints. Process must be done within the
defined constraints or the system will fail. An example
is the operating system for a flight control computer or
an advanced jet airplane. Often used as a control device
in a dedicated application such as controlling
scientific experiments, medical imaging systems,
industrial control systems, and some display systems.
Real-Time systems may be either hard or soft real-time.
Hard real-time: Secondary storage limited or absent,
data stored in short term memory, or read-only memory
(ROM), Conflicts with time-sharing systems, not
supported by general-purpose operating systems. Soft
real-time: Limited utility in industrial control of
robotics, Useful in applications (multimedia, virtual
reality) requiring advanced operating-system features.
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