NAME: SHANAZ N KANDIRA
STUDENT NUMBER: B211025B
COURSE CODE: SWE 111
COURSE NARRATION: OPERATING SYSTEMS CONCEPTS
LEVEL: 1.2
ASSIGNMENT 1
(1a) An interrupt is an event that alters the sequence in which the
processor executes instructions. An interrupt might be planned
(specifically requested by the currently running program) or
unplanned (caused by an event that might or might not be related to
the currently running program). It is a change in program defined
flow of execution. When it occurs, the hardware executes the
instructions at a specified address instead of following the normal
flow. Interrupts fall into classes which include:
(i)Timer
-Generated by a timer within the processor. This allows the
operating system to perform certain functions on a regular basis.
(ii) Input or Output (I/O)
-Generated by an I/O controller, to signal normal completion of an
operation or to signal a variety of error conditions
(iii) Hardware Failure
- Generated by a failure such as power failure or memory parity
error.
(iv) Program
-Generated by some condition that occurs as a result of an
instruction execution, such as arithmetic overflow, division by zero,
attempt to execute an illegal machine instruction, or reference outside
a user’s allowed memory space.
(bi) Keeps track of all memory locations free or allocated and if
allocated, to which processes and how much.
(ii) To decide memory allocation policy like which process should get
how much memory when and where.
(iii) To use various techniques and algorithm to allocate or de-allocate
memory locations.
(c) User mode is the mode in which the applications are running whilst
kernel mode is the privileged mode to which the computer enters when
accessing hardware resources.
-This distinction allows the user to select the appropriate mode as
kernel mode can access both user programs as well as kernel programs
there are no restrictions unlike in user mode.
(d) One gains the advantage of local spooling and rendering of print
jobs and those jobs go directly from the workstation to the printer. This
is the most efficient way of printing and reduces overall network traffic.
A driver issue or a job stuck in the queue will only affect one user.
Printing directly to the printer is a slower process than spooling.
(2)a Swapping is a mechanism in which a process can be moved
temporarily out of main memory (or swapped) to secondary storage
(disk) and make that memory available to other processes. At some
later time, the system swaps back the process from the secondary
storage to main memory.
(bi) fixmbr command is a recovery console command that writes a new
master boot record to the hard disk drive that you specify.
(ii) chkdsk is a command that displays a status report for a volume such
as a disk, and can correct any errors found in that volume.
(c)
(4a) I. Locate the file to be examined, right-click on the icon, and select
properties.
2. This opens a new window initially showing basic information about
the file. Navigate the second tab in the window, labeled permissions.
3. There, you will see that the permission for each file differs according
to three categories: ….owner (the user who created the file/directory).
…..group (to which the owner belongs to).
….others (all other users).
--for each file, the owner can grant or restrict access to users according
to the categories they fall in.
(b) one needs to make use of the usermod command.
-: gain root in the terminal with sudo –s or su, to modify your
username.
-: run the usermod command below, and replace newlogin and
oldlogin.
-Newlogin should be the new username you would like to have, and
oldlogin should be the old one.
(c) to add user to a certain group, use the usermod command. To add a
user to a group, specify the –a-G flags. These should be followed by the
name of the group to which you want to add a user and the user’s
username.
To remove a member from supplementary group, execute the
usermod command listing the supplementary groups that you want the
user to remain a member of, where user-name is the user name.
(d) linux kernel is the heart of the operating system. Without the
kernel, we simply cannot perform any task, since it is mainly
responsible for the software and hardware of our computer working
correctly and can interact with each other.
