Multitasking Operating Systems (Windows)
Introduction:
A multitasking operating system (OS) is designed to execute multiple tasks or
processes simultaneously or in a way that gives the illusion of simultaneous
execution. In a multitasking OS like Windows, the system allows users to run
multiple programs at the same time, improving productivity, efficiency, and
resource utilization. Windows is a highly efficient multitasking operating system
that manages CPU, memory, and other resources to ensure smooth operation of
multiple applications and background processes concurrently.
Types of Multitasking in Windows:
1. Preemptive Multitasking:
o Preemptive multitasking is the core mechanism used by modern
versions of Windows (starting from Windows NT). It enables the
operating system to control when and how processes are executed.
In this model, the operating system’s kernel decides when to pause
or resume a process.
o The CPU time is divided into small slices, and each running task or
process is given its turn based on the priority levels set by the OS. A
process can be interrupted or "preempted" by the system to allow
higher-priority processes to execute.
o This approach improves system responsiveness and ensures that no
single process can dominate the system, contributing to better
overall stability.
2. Cooperative Multitasking (Legacy Windows):
o Cooperative multitasking was used in older versions of Windows,
such as Windows 3.x. In this model, each process voluntarily gives up
control of the CPU after completing its task. While this worked well
for basic applications, it was unreliable and prone to crashes.
o If one application failed to release the CPU, the entire system could
freeze. As a result, Windows transitioned to preemptive multitasking
in Windows 95 to improve system stability and responsiveness.
, Key Features of Multitasking in Windows:
1. Task Scheduling:
o Task scheduling is a critical aspect of multitasking. Windows uses a
task scheduler to manage the allocation of the CPU to different
tasks. The scheduler is responsible for determining which process
runs next based on its priority, resource requirements, and fairness.
o Priority Levels: Each process has an associated priority level,
determining how much CPU time it should receive relative to other
tasks. Higher-priority tasks are given more CPU time, while lower-
priority tasks may be delayed if system resources are limited.
o Windows employs several scheduling algorithms, such as round-
robin scheduling, which allocates CPU time in small slices to each
process, and priority-based scheduling, where high-priority
processes are allocated CPU time before lower-priority ones.
2. Process Management:
o In a multitasking environment, each running program or application
is treated as a process. Windows creates a Process Control Block
(PCB) for each process, which contains important information like
the process’s current state, memory usage, and CPU registers.
o The Task Manager in Windows provides users with a graphical
interface to monitor and manage running processes. It allows users
to view the CPU and memory usage of each process and terminate
unresponsive or unwanted applications.
3. Context Switching:
o Context switching is the process by which the operating system
saves the state of a currently running task and loads the state of
another task. Each task has its own context, which includes its
current position in the program, its register values, and other
relevant information.
o Windows performs context switching whenever the CPU switches
between processes, which happens frequently in a multitasking
system. This enables the operating system to give the illusion of
simultaneous execution, even on systems with a single processor.
Introduction:
A multitasking operating system (OS) is designed to execute multiple tasks or
processes simultaneously or in a way that gives the illusion of simultaneous
execution. In a multitasking OS like Windows, the system allows users to run
multiple programs at the same time, improving productivity, efficiency, and
resource utilization. Windows is a highly efficient multitasking operating system
that manages CPU, memory, and other resources to ensure smooth operation of
multiple applications and background processes concurrently.
Types of Multitasking in Windows:
1. Preemptive Multitasking:
o Preemptive multitasking is the core mechanism used by modern
versions of Windows (starting from Windows NT). It enables the
operating system to control when and how processes are executed.
In this model, the operating system’s kernel decides when to pause
or resume a process.
o The CPU time is divided into small slices, and each running task or
process is given its turn based on the priority levels set by the OS. A
process can be interrupted or "preempted" by the system to allow
higher-priority processes to execute.
o This approach improves system responsiveness and ensures that no
single process can dominate the system, contributing to better
overall stability.
2. Cooperative Multitasking (Legacy Windows):
o Cooperative multitasking was used in older versions of Windows,
such as Windows 3.x. In this model, each process voluntarily gives up
control of the CPU after completing its task. While this worked well
for basic applications, it was unreliable and prone to crashes.
o If one application failed to release the CPU, the entire system could
freeze. As a result, Windows transitioned to preemptive multitasking
in Windows 95 to improve system stability and responsiveness.
, Key Features of Multitasking in Windows:
1. Task Scheduling:
o Task scheduling is a critical aspect of multitasking. Windows uses a
task scheduler to manage the allocation of the CPU to different
tasks. The scheduler is responsible for determining which process
runs next based on its priority, resource requirements, and fairness.
o Priority Levels: Each process has an associated priority level,
determining how much CPU time it should receive relative to other
tasks. Higher-priority tasks are given more CPU time, while lower-
priority tasks may be delayed if system resources are limited.
o Windows employs several scheduling algorithms, such as round-
robin scheduling, which allocates CPU time in small slices to each
process, and priority-based scheduling, where high-priority
processes are allocated CPU time before lower-priority ones.
2. Process Management:
o In a multitasking environment, each running program or application
is treated as a process. Windows creates a Process Control Block
(PCB) for each process, which contains important information like
the process’s current state, memory usage, and CPU registers.
o The Task Manager in Windows provides users with a graphical
interface to monitor and manage running processes. It allows users
to view the CPU and memory usage of each process and terminate
unresponsive or unwanted applications.
3. Context Switching:
o Context switching is the process by which the operating system
saves the state of a currently running task and loads the state of
another task. Each task has its own context, which includes its
current position in the program, its register values, and other
relevant information.
o Windows performs context switching whenever the CPU switches
between processes, which happens frequently in a multitasking
system. This enables the operating system to give the illusion of
simultaneous execution, even on systems with a single processor.
