OPERATING SYSTEM AND ITS FUNCTIONS
GROUP 6
SCENARIO
• When a brand new computer comes off the factory
assembly line, it can do nothing. The hardware needs
software to make it work. We don’t mean just application
software(e.g. Ms Word)
WHY NOT?
• Because an applications software cannot communicate
directly with the hardware.
THEN HOW DOES A
COMPUTER WORK?
WITH THE OPERATING SYSTEM
An operating system works by allowing hardware to communicate
with software.
It lies between applications software and the computer hardware like
a translator.
DEFINITION
• It is a system software.
• It runs in the background of a
computer system
• It makes communication possible
between software and hardware
• Without and OS the computer
will be hard to use.
WHAT ARE THE
FUNCTIONS OF THE OS?
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Memory management
Provides user- computer interface
Processor management for multitasking
Batch processing
Real time processing
Interrupt handling
Error handling
Controls inputs/outputs
Management of hardware /peripherals
Security
Running /loading of software
File utilities
MEMORY MANAGEMENT
• When you load an application, the OS will copy the application to
the RAM.
• It will ensure that each program that loads has its own space on the
RAM.
• This stops other programs reading and writing to the memory area
for another application.
• It is also responsible for managing virtual memory.
Provides computer-user interface
• The word interface means ‘coming together’.
• In computers, an interface enables a user to
interact with a computer.
• Operating Systems provide users with an interface
so that they can interact with the computer.
• Operating systems will usually offer one of two
major types of interface:
- Graphical User Interface (GUI)
- Command Line Interface
TYPES OF USER INTERFACES
• Graphical User Interfaces
Uses windows, icons, menus and pointers (WIMP) to
control the computer.
• Command Line Interface
Used to be the only way to interact with a computer
(pre-80s) and is still used today by ‘Linux users’ and
other professionals with technical knowledge. With
this kind of interface ‘written commands’ control
computers.
PERIPHAL MANAGEMENT
• Peripherals are devices that are attached to a computer such as a printer or
speakers.
• The operating system controls these devices and gives programs access to them.
e.g. When you print a document, the program doesn’t know how to talk to the
printer, it doesn’t even know if one is installed. It passes this data to the operating
system which in turn passes it to the printer.
MULTITASKING
• As we know, a CPU works one process at a time.
User
• An operating system manages the CPU’s processes so
that several programs can run at once.
Operating System
• On old computers, a CPU would focus on the
processes of one program.
App
App
App
• On a multi-tasking operating system, many programs
can run at the same time.
• The operating system enables this by:
• either allowing processes to happen in turns, one by one
• or getting the shortest job done first
• It switches between the programs many times.
• Because CPU’s are so quick now-a-days, it appears to be
simultaneous and allows many programs to be used at once.
BATCH PROCESSING
• Batch processing is a technique in which an Operating System
collects the programs and data together in a batch before
processing starts.
An operating system does the following
activities related to batch processing −
• The OS defines a job which has predefined sequence of commands,
programs and data as a single unit.
• The OS keeps a number a jobs in memory and executes them without any
manual information.
• Jobs are processed in the order of submission, i.e., first come first served
fashion.
• When a job completes its execution, its memory is released and the
output for the job gets copied into an output spool for later printing or
processing.
REAL TIME PROCESSING
• Real-time data processing is the execution of data in
a short time period, providing near-instantaneous
output.
• The processing is done as the data is inputted, so it
needs a continuous stream of input data in order to
provide a continuous output
ERROR HANDLING & INTERRUPT MANAGEMENT
• When an error is detected, the operating systems performs checks
on the hardware, software and the activities of the user on the
computer to identify error.
• A interrupt is a signal sent from a device or software to the
processor. This will cause the processor to temporarily stop what it is
doing and service the interrupt. This can happen when ;
• disk drive is ready to receive more data
• Hardware/software error has occurred (e.g. paper jammed in the printer)
• <ctrl><Alt><Del> buttons are pressed
• An interrupt handler takes into account all of these signals and
prioritizes them in a queue in order to figure out which one to deal
with first.
ERROR HANDLING
SECURITY
• Operating systems manage computer users and ensure that
a user’s data is only seen by them and not by others.
• They give users ‘usernames’ and ‘passwords’ so that data is
kept secure.
• They also give different users different permissions.
• This means that one user may be given permission to install
new programs whereas others cannot.
• FILE UTILITIES:
• COPY,PASTE, SAVE, SORT, DELETE
• LOADING /EXECUTING PROGRAMS:
• A program is loaded in the memory before it can be executed. Operating system
provides the facility to load programs in memory easily and then execute it.
• INPUT/OUTPUT CONTROL:
The OS must ensure that the devices are used correctly and fairly by the executing
programs.
• For example, a printer must be managed so that the outputs from two different
programs are not mixed together. A disk drive must be managed so that all programs
get fair use of the disk for reads and writes.
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• A device like a microwave has just a
dedicated OS and a microprocessor.
• This is because it;
• preforms one task
• Has very straightforward inputs
• Has simple never changing hardware
THANK YOU
PRESENTATION BY:
JB
DANIEL
CHARITY
CHIBUIKEM