INTRODUCTION
SYSTEMS
TO
OPERATING
Basic Knowledge
Name- Ankit Rawat
Course- BCA
Section- B
Class Roll no.-8
Student Id.- 21041257
What is an Operating System?
An Operating system is basically a intermediary agent between the user
and the computer hardware.
Manages the computer’s resources (hardware, abstract resources,
software)
It’s a resource allocator.
It is also used to control programs to prevent errors and improper
computer use.
It is interrupt driven.
Operating System Benefits
Simplifies hardware control for applications
Enforcer of sharing, fairness and security with the goal of better overall
performance
Trade-off between fairness and performance
Trade-off between optimal algorithms and lean algorithms – OS is
overhead.
Provides abstract resources
Sockets
Inter-process communication
History of Operating Systems
Earliest computers had no Operating System
Batch Processing
A typical computer in the 1960s and 70s was a large machine. Its processing
was managed by a human operator. The operator would organize various jobs
from multiple users into batches.
Timesharing
A timesharing system allows multiple users to interact with a computer at the same time
Multiprogramming allowed multiple processes to be active at once, which gave rise to the
ability for programmers to interact with the computer system directly, while still sharing its
resources
In a timesharing system, each user has his or her own virtual machine, in which all system
resources are (in effect) available for use
System Concepts: Processes
Processes are a very important concept in Operating Systems and lie at the heart of most
of its tasks. A process, which is a program in execution, goes through the cycle of starting,
performing its task and then exiting.
When are processes created?
1. On system startup. Daemons, or background processes, are
automatically started by the Operating System when the system is
initialized and they work in the background either listening for events
to occur or maintaining some part of the system.
2. On system calls. A process that is already running may wish to give
birth to additional processes to help it in a particular task. The latter
processes are known as child processes and the former is the parent. It
is common to have such a hierarchy of processes.
3. On user requests. Double clicking on a program icon or executing it
via the command line automatically creates a process for that program.
It is more than likely that it will then generate child processes
When are processes terminated?
1. When they're done.
After it completes its tasks, a process
voluntarily exits.
2. When an error occurs.
If an error occurs that the process
cannot ignore or avoid, it voluntarily exits.
3. When a fatal error occurs.
A program directly referencing
memory (in a language such as C, which allows this) may be
referring to data that is nonexistent. In such a case, the system
has no option but to kill the process to prevent it from corrupting
other processes' data.
Operating System Concepts: Memory Management
Memory management is an extremely important part of an Operating
System's responsibilities. Memory is a limited resource, and as such, it
has to be carefully managed. The OS must:
1. Keep track of memory that's in use and memory that isn't.
2. Allocate and deallocate memory to processes that require it.
3. Swap data between main memory and disk when main memory fills
up.
There are three types of memory in every system:
1. Volatile: Fast, expensive and small cache memory, made up of the
same material as the CPU.
2. Volatile: Medium-speed and medium-size Random Access Memory
Operating systems must accomplish the following tasks:
Processor management. The operating system needs to
allocate enough of the processor's time to each process and
application so that they can run as efficiently as possible. This
is particularly important for multitasking. When the user has
multiple applications and processes running, it is up to the
operating system to ensure that they have enough resources
to run properly.
Memory storage and management. The operating system
needs to ensure that each process has enough memory to
execute the process, while also ensuring that one process does
not use the memory allocated to another process.
Device management. Most computers have additional hardware, such as
printers and scanners, connected to them. These devices require drivers,
or special programs that translate the electrical signals sent from the
operating system or application program to the hardware device. The
operating system manages the input to and output from the computer. It
often assigns high-priority blocks to drivers so that the hardware can be
released and available for the next use as soon as possible.
Application interface. Programmers use application program interfaces
(APIs) to control the computer and operating system. As software
developers write applications, they can insert these API functions in their
programs. As the operating system encounters these API functions, it
takes the desired action, so the programmer does not need to know the
details of controlling the hardware.
User interface. The user interface sits as a layer above the operating
system. It is the part of the application through which the user interacts
with the application. Some operating systems, such as Microsoft Windows
and Apple Macintosh, use graphical user interfaces. Other operating
systems, such as Unix, use shells.
The most popular operating system today is Microsoft's Windows
operating system.
Macintosh computers have their own operating system, the most
recent of which is called Mac OS X.
There are also open source operating systems such as Linux.