2015816
Description
Mind Map by bubblesthelabrad, updated more than 1 year ago
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Created by bubblesthelabrad
almost 10 years ago
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Operating Systems
- Modes of
operating
systems
- Single-User
Single Process
- allow the machine to be
operated by only one user at
a time with at most one
application program loaded
into main memory.
- It can only deal
with one set of
input devices
- Operating systems for
handheld devices and
also DOS
- allow the machine to be
operated by only one user at
a time with at most one
application program loaded
into main memory.
- Multi-Programming
- Permits multiple
programs to be active at
once with the operating
system allowing each one
a small ‘time-slice’ of
processor time in turn
- Virtual memory
divides each program
into pages. However,
only a few pages of
the program stored in
memory at any one
time
- A multi-programming
operating system
balances the sharing of
the processor among the
application programs in
order to achieve a good
service to all.
- Permits multiple
programs to be active at
once with the operating
system allowing each one
a small ‘time-slice’ of
processor time in turn
- Multi-Tasking
- Modern operating
systems are
multi-tasking
- The user can
switch between
one application
and another
- The computer is still only
processing one thing at a
time, but use of time slices
makes it appear to the
user that it is happening
simultaneously
- Multi-tasking is
the concurrent
execution of two
or more tasks
- Modern operating
systems are
multi-tasking
- Batch-Processing
- In batch-processing
mode, processing is
carried out from
beginning to end
without user
interaction.
- Jobs prepared in this
way have all their
processing
requirements
defined in advance.
- By using multiprogramming,
a batch of several jobs can
be loaded so that when
executed over the same time
period the processor is kept
as busy as possible by
switching between the jobs
as and when necessary
- Increases throughput
- The total number of jobs
completed per unit time, and
reduces the turnaround time
- The total number of jobs
completed per unit time, and
reduces the turnaround time
- Allows sharing of
computer resources
among many users
and programs
- Keeps costs down
- Moves the time
of job processing
to when the
computing
resources are less
busy
- Increases throughput
- Examples are:
Deleting temporary
files or unused
desktop icons.
Archive and
compression of old
emails. Scheduled
virus scans
- In batch-processing
mode, processing is
carried out from
beginning to end
without user
interaction.
- Multi-Access
- A number of users
are connected to a
central computer
and seemingly have
individual control
- The central
computer (server)
determines which
user is waiting for
processing
(polling).
- Polling is checking the
status of a device, as
part of a repeated
cycle.
- Each user is
allocated a
time-slice of
processing time
- Polling is checking the
status of a device, as
part of a repeated
cycle.
- A number of users
are connected to a
central computer
and seemingly have
individual control
- Single-User
Single Process
- Scheduling
- The method by which
threads, processes or data
flows are given access to
system resources
- Usually done to load
balance and share
system resources
effectively or achieve a
target quality of service
- Usually done to load
balance and share
system resources
effectively or achieve a
target quality of service
- The method by which
threads, processes or data
flows are given access to
system resources
- Types of the
operating
system
- Interactive Processing
- User supplies
commands
and data
- User supplies
commands
and data
- Real Time
- Handles events
in parallel,
responds within a
set time
- Handles events
in parallel,
responds within a
set time
- Disk operating system
- Organises
drives, folds and
files
- Organises
drives, folds and
files
- File Managment
- Manages files,
storage, and
access rights
- Manages files,
storage, and
access rights
- Network
- When a
number of
computers are
interconnected
- When a
number of
computers are
interconnected
- Batch Processing
- Doing several
jobs without user
interaction
- Doing several
jobs without user
interaction
- Interactive Processing
- Buffers
- A buffer is an
area of reserved
memory which
temporarily stores
data that is in
transit.
- Buffers are
used for input
and output of
data.
- Data is input
from a file
(e.g. from a
hard drive)
one block at a
time.
- When data is to be
output to a file, it is
stored in a buffer, and
is only transferred to
the file when the
buffer is full.
- Keeps the number
of transfers to a
minimum and saves
time
- Needs some
memory space
for the buffer
- Overcome the problem
of different speeds of
peripherals and
processors - processors
operate thousands of
times faster than
printers
- Interrupts are important in bufers.
As well as messages about buffer
overflow interrupts can be
between any peripheral device and
the processor. It might be a
message from a device saying
there is a hardware failure
- Keeps the number
of transfers to a
minimum and saves
time
- A buffer is an
area of reserved
memory which
temporarily stores
data that is in
transit.
- Operating
systems
Functions
- Process
managment
- Memory
Managment
- I/O
Control
- File
Managment
- Process
managment
- Scheduling
- B = Ready and A = Running
- B = Running and A = Blocked
- B = Running and A = Ready
- B = Running and A = Ready
- B = Running and A = Blocked
- Tries to
maximize as
many jobs as
possible
- Maximize
the user
processes
- Avoid the low
priority jobs staying
at the back of the
queue
- Avoid the low
priority jobs staying
at the back of the
queue
- B = Ready and A = Running
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