INTRODUCTION TO OPERATING SYSTEM
SEMAPHORES
A semaphore, in its most basic form, is a protected integer variable that can facilitate and restrict access
to shared resources in a multi-processing environment.
In 1965, Dijkstra proposed a new and very significant technique for managing concurrent
processes by using the value of a simple integer variable to synchronize the progress of
interacting processes. This integer variable is called semaphore.
PROGRAM-A set of instruction that instruct a computer on what to do in a given time to
meet a given objective.
PROCESS-This is program in execution. Refers to a program executing
RACE CONDITION-This is a shared program executing and determining which process
sharing will write first.
SYSTEM CALL-This is a request made by a process to an operating system. Or a request
made to an operating system by a process
MONITORS
Monitors are a synchronization construct that were created to overcome the problems caused by
semaphores such as timing errors.
Monitors are abstract data types and contain shared data variables and procedures. The shared data
variables cannot be directly accessed by a process and procedures are required to allow a single
process to access the shared data variables at a time.
SHELL
A shell is a primary interface between the operating system and users
Definition: The operating system is the most important program that is on a computer. The
operating system basically runs the computer and allows other programs to run as well. The
operating system does all the basic things that a computer needs to do, such as recognizing inputs
from the mouse or the keyboard. It keeps track of where all the files are on the computer. It
allocates resources to the various programs that are running and it prevents unauthorized access to
the computer.
, An operating system, abbreviated OS, is a product, software type that is part of a system,
equipment or computerized equipment, which deals with management and coordination of its
activities. The computerized system may be a computer, a workstation, a server, a PC, a notebook, a
smartphone, a road navigation device or another system with "intelligence" of its own. The
operating system plays the role of host for all applications running on the equipment (hardware).
OPERATING SYSTEM FUNCTIONS
To act as interface between hardware and users, an operating system must be able perform the
following functions:
1. Enabling startup application programs. Thus, the operating system must have:
- A text editor
- A translator
- An editor of links
2. The allocation of resources needed to execute programs is done by identifying: the programs that
are running, the need for memory, peripheral devices and data protection requirements.
3. Facilities for data compression, sorting, mixing, cataloging and maintenance of libraries, through
utility programs available.
4. Plan implementation works according to certain criteria, for efficient use of central processing
unit.
5. Assisting implementation of programs through computer-user communication system, at both
hardware and software level.
Examples of operating systems: MS-DOS, LINUX, SOLARIS, MAC OS, UNIX, WINDOWS
Definition: An operating system (OS) is a set of computer program that manages the hardware and
software resources of a computer. At the foundation of all system software, the OS performs basic
tasks such as controlling and allocating memory, prioritizing system requests, controlling input and
output devices, facilitating networking, and managing files. It also may provide a graphical user
interface for higher level functions. Various services performed by operating systems are discussed
below.
Process management: It deals with running multiple processes. Most operating system allows
a process to be assigned a priority which affects its allocation of CPU time. Interactive operating
systems also employ some level of feedback in which the task with which the user is working
receives higher priority. In many systems there is a background process which runs when no other
process is waiting for the CPU.
SEMAPHORES
A semaphore, in its most basic form, is a protected integer variable that can facilitate and restrict access
to shared resources in a multi-processing environment.
In 1965, Dijkstra proposed a new and very significant technique for managing concurrent
processes by using the value of a simple integer variable to synchronize the progress of
interacting processes. This integer variable is called semaphore.
PROGRAM-A set of instruction that instruct a computer on what to do in a given time to
meet a given objective.
PROCESS-This is program in execution. Refers to a program executing
RACE CONDITION-This is a shared program executing and determining which process
sharing will write first.
SYSTEM CALL-This is a request made by a process to an operating system. Or a request
made to an operating system by a process
MONITORS
Monitors are a synchronization construct that were created to overcome the problems caused by
semaphores such as timing errors.
Monitors are abstract data types and contain shared data variables and procedures. The shared data
variables cannot be directly accessed by a process and procedures are required to allow a single
process to access the shared data variables at a time.
SHELL
A shell is a primary interface between the operating system and users
Definition: The operating system is the most important program that is on a computer. The
operating system basically runs the computer and allows other programs to run as well. The
operating system does all the basic things that a computer needs to do, such as recognizing inputs
from the mouse or the keyboard. It keeps track of where all the files are on the computer. It
allocates resources to the various programs that are running and it prevents unauthorized access to
the computer.
, An operating system, abbreviated OS, is a product, software type that is part of a system,
equipment or computerized equipment, which deals with management and coordination of its
activities. The computerized system may be a computer, a workstation, a server, a PC, a notebook, a
smartphone, a road navigation device or another system with "intelligence" of its own. The
operating system plays the role of host for all applications running on the equipment (hardware).
OPERATING SYSTEM FUNCTIONS
To act as interface between hardware and users, an operating system must be able perform the
following functions:
1. Enabling startup application programs. Thus, the operating system must have:
- A text editor
- A translator
- An editor of links
2. The allocation of resources needed to execute programs is done by identifying: the programs that
are running, the need for memory, peripheral devices and data protection requirements.
3. Facilities for data compression, sorting, mixing, cataloging and maintenance of libraries, through
utility programs available.
4. Plan implementation works according to certain criteria, for efficient use of central processing
unit.
5. Assisting implementation of programs through computer-user communication system, at both
hardware and software level.
Examples of operating systems: MS-DOS, LINUX, SOLARIS, MAC OS, UNIX, WINDOWS
Definition: An operating system (OS) is a set of computer program that manages the hardware and
software resources of a computer. At the foundation of all system software, the OS performs basic
tasks such as controlling and allocating memory, prioritizing system requests, controlling input and
output devices, facilitating networking, and managing files. It also may provide a graphical user
interface for higher level functions. Various services performed by operating systems are discussed
below.
Process management: It deals with running multiple processes. Most operating system allows
a process to be assigned a priority which affects its allocation of CPU time. Interactive operating
systems also employ some level of feedback in which the task with which the user is working
receives higher priority. In many systems there is a background process which runs when no other
process is waiting for the CPU.
