The document outlines the role of interrupts in operating systems, detailing how they allow the CPU to respond to signals from hardware or software, manage device communication through interrupt service routines (ISRs), and facilitate task scheduling and resource management. It explains the process of handling interrupts, including interrupt generation, execution of ISRs, and the resumption of the interrupted program. Key functions of interrupts include handling asynchronous events, managing I/O operations, and addressing error conditions.

1. ASSIGNMENT NO :1
SUBMITTED TO: Ms.Saima
SUBMITTED BY: Ali jan
SUBJECT: Operating system
Department: CS&IT
CLASS: 4th Evening Session (B)

2. 1. Interrupt Handling:
Interrupts are signals sent by hardware or
software to the CPU to request its attention.
When an interrupt occurs, the CPU temporarily
stops its current execution and transfers
control to a specific interrupt handler routine.
The operating system manages these interrupt
handlers.

3. 2- Interrupt Service Routines (ISRs):
 These are small segments of code within the
operating system that handle specific types of
interrupts. When an interrupt occurs, the CPU
looks up the appropriate ISR and executes it.
ISRs typically handle tasks such as servicing
I/O devices, handling timer events, or
managing errors

4. 3-Device Drivers:
 Device drivers are software components
within the operating system that enable
communication between the operating
system and peripheral devices such as
keyboards, mice, disks, and network
interfaces. When an interrupt is generated by
a device, the corresponding device driver's
ISR is invoked to handle the interrupt and
perform any necessary actions.

5. 4-Interrupt Prioritization and Handling:
 The operating system manages interrupt
prioritization to ensure that critical tasks are
handled promptly. It may prioritize interrupts
based on their importance and the needs of
the system. The operating system may also
employ techniques such as interrupt masking
and interrupt nesting to manage multiple
interrupts efficiently.
5-Context Switching:
Interrupts can trigger context switches, where
the CPU switches from executing one process
to another. The operating system is
responsible for managing the state

6. of the interrupted process, saving its context,
and restoring the context of the newly
scheduled process.
6-Resource Management:
 The operating system coordinates access to
system resources among different processes
and devices. Interrupts play a crucial role in
resource management by allowing devices to
signal when they need attention or when data
is ready to be processed.

7.  Interrupts "drive" the actions of the operating
system by serving as triggers for various
essential tasks and events.
1-Asynchronous Events Handling:
 Interrupts allow the operating system to handle
asynchronous events generated by hardware
devices or other software processes. For
example, when a keyboard sends a signal
indicating that a key has been pressed, an
interrupt is generated, prompting the operating
system to read and process the input.

8. 2-Task Scheduling:
 Interrupts play a crucial role in task
scheduling by allowing the operating system
to preempt the currently executing task and
switch to another task when necessary. For
instance, a timer interrupt can trigger a
context switch to ensure that multiple
processes receive fair access to the CPU.
3- I/O Operations:
 Interrupts are essential for managing
input/output operations. When a peripheral
device completes an I/O operation or requires
attention, it generates an interrupt,
prompting the operating system to initiate or
complete the corresponding I/O operation.

9. 4-Error Handling:
 Interrupts are used for error handling and
recovery within the operating system. When
hardware errors or exceptional conditions occur,
interrupts can notify the operating system,
enabling it to take appropriate corrective actions
or generate error messages.
5-Resource Management:
 Interrupts facilitate resource management by
allowing devices to signal when they require
attention or when data is available for
processing. This helps the operating system
efficiently manage system resources such as CPU
time, memory, and I/O devices.

10. 1-Interrupt Generation:
 Hardware Interrupts: Hardware devices such as
timers, I/O controllers, or other peripherals
generate hardware interrupts to signal events
requiring the CPU's attention. For example, when
a key is pressed on the keyboard, the keyboard
controller may generate an interrupt.
 Software Interrupts: Software interrupts, also
known as traps or exceptions, are generated by
the CPU in response to exceptional conditions
detected during program execution, such as
division by zero or invalid memory access

11. 2-Interrupt Handling by the CPU:
 When an interrupt occurs, the CPU temporarily
suspends the execution of the currently running
program.
 The CPU saves the current state of the program,
including the program counter (PC) and other
relevant registers, onto the stack or in
designated memory locations.
 The CPU then determines the type of interrupt
that occurred and identifies the corresponding
interrupt handler routine to execute. This
involves consulting an interrupt vector table or a
similar data structure that maps interrupt
numbers or types to the addresses of the
corresponding interrupt handler routin

12. 3-Execution of Interrupt Service Routine (ISR):
The CPU transfers control to the appropriate
interrupt handler routine, also known as the
Interrupt Service Routine (ISR) or Interrupt Handler.
The ISR performs the necessary actions to handle
the interrupt. This may involve tasks such as
servicing the hardware device that triggered the
interrupt, updating system state, or initiating I/O
operations.
The ISR may interact with device drivers, perform
data transfer operations, or communicate with
other system components as needed to handle the
interrupt.

13. 4-Interrupt Acknowledgment:
In some systems, especially in older architectures,
the CPU may need to send an acknowledgment
signal to the interrupt controller or the interrupting
device to confirm receipt of the interrupt request.
This step may involve acknowledging the interrupt
at the hardware level to prevent the same interrupt
from being re-triggered.
5-Resumption of Program Execution:
After the ISR completes its execution, the CPU
restores the saved state of the interrupted program,
including the program counter and register values.
The CPU resumes execution of the interrupted
program from the point where it was interrupted,
allowing the program to continue its execution as if
the interrupt had not occurred.