Transcript operating systems

What is an Operating System?
An operating system is the
software that makes everything in
the computer work together
smoothly and efficiently.
Functions of Operating Systems
Operating systems have three
basic jobs they must do:
Control Hardware
Run Applications
Manage data and files
Functions of Operating Systems
Control Hardware
they control access to and allocation of
resources. Imagine if your printer
received print instructions from two
different programs and began printing
from both of them simultaneously.
Functions of Operating Systems
 Run Applications
The operating system determines which
programs will have access to the CPU
and under what conditions. Similarly,
the operating system controls which
program can write data to a disk, or
draw something on the screen.
Functions of Operating Systems
Manage Data and Files
The third characteristic of operating systems
is the they create a user interface through
which the user interacts with the computer. In
the earliest computers, the interface
consisted of things like punched cards and
paper tape, created by specialized keyboard
devices.
Types of Operating Systems
Windows 95/98 - This is what
you will find on most new PC's
today. It is a very popular OS, and
there are many applications that
run on it. It has an easy-to-use
Graphical User Interface (GUI).
Types of Operating Systems
Windows NT - Windows NT is
another Microsoft operating
system that is beginning to really
catch on because of it's networking
capabilities. Microsoft is trying to
slowly phase out Windows 95/98
and replace it with some form of
NT.
Types of Operating Systems
Macintosh System 7/8 - This is
the operating system found on the
Macintosh brand of computers.
This was one of the first GUI's to
become popular. Macs have the
history of being easy to use, and
coming equipped with all the
hardware you'll need.
Types of Operating Systems
UNIX is a command prompt OS,
much like the now defunct
Microsoft DOS operating system.
Unix is by far the oldest of the
operating systems, having been in
existence for a good 20 years.
MS-DOS Operating
System
is a command line user interface.
MS-DOS 1.0 was released in 1981 for
IBM computers and the latest version of
MS-DOS is MS-DOS 6.22 released in
1994.
While MS-DOS is not commonly used by
itself today, it still can be accessed from
Windows 95, Windows 98 or Windows
ME.
Operating SystemsClassification
Operating systems can be classified as follows:
multi-user : Allows two or more users to run programs
at the same time. Some operating systems permit
hundreds or even thousands of concurrent users.
multiprocessing : Supports running a program on
more than one CPU.
multitasking : Allows more than one program to run
concurrently.
multithreading : Allows different parts of a single
program to run concurrently.
real time: Responds to input instantly. Generalpurpose operating systems, such as DOS and UNIX,
are not real-time.
Operating SystemsClassification
Multi-user
Refers to computer systems that support two
or more simultaneous users.
All mainframes and minicomputers are multiuser systems, but most personal computers
and workstations are not.
Another term for multi-user is time sharing.
Operating SystemsClassification
Multiprocessing
Refers to a computer system's ability to
support more than one process (program) at
the same time.
Multiprocessing operating systems enable
several programs to run concurrently.
UNIX is one of the most widely used
multiprocessing systems.
Refers to the utilization of multiple CPUs in a
single computer system. This is also called
parallel processing.
Operating SystemsClassification
Multitasking
The ability to execute more than one task at
the same time, a task being a program.
The terms multitasking and multiprocessing
are often used interchangeably, although
multiprocessing sometimes implies that more
than one CPU is involved.
In multitasking, only one CPU is involved, but
it switches from one program to another so
quickly that it gives the appearance of
executing all of the programs at the same
time.
Operating SystemsClassification
Multithreading
The ability of an operating system to
execute different parts of a program,
called threads, simultaneously.
The programmer must carefully design
the program in such a way that all the
threads can run at the same time
without interfering with each other.
Operating SystemsClassification
Real time
They are used for such tasks as navigation, in
which the computer must react to a steady
flow of new information without interruption.
Real time can also refer to events simulated
by a computer at the same speed that they
would occur in real life.
In graphics animation, for example, a realtime program would display objects moving
across the screen at the same speed that
they would actually move.