Computer Interrupts and System Calls

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Questions and Answers

What is the primary purpose of time sharing in computing?

To improve the performance of a single-user system.

To let multiple users share the same computer system concurrently. (correct)

To allow multiple users to use different computer systems simultaneously.

To enable a single user to access multiple systems without delay.

How does buffering work in the context of speed differences between operations?

It slows down faster operations to match the slower ones.

It prevents slower operations from causing delays in faster operations. (correct)

It eliminates the need for any operational delays.

It exclusively allows the faster operation to proceed without interruption.

Which scenario best illustrates zero capacity buffering?

A cashier pausing while the bagger finishes their first item.

A cashier scanning items without a bagger present. (correct)

A cashier placing items into a full basket, waiting for space.

A cashier continuously scanning while the bagger works at their pace.

What does bounded capacity refer to in buffering?

A buffer that has limited space and can become full. Signup and view all the answers

What happens with unbounded capacity buffering?

The cashier can operate without interruptions no matter the bagger's speed. Signup and view all the answers

In the example of buffering, who represents the CPU?

The cashier who scans items quickly. Signup and view all the answers

What would be a consequence of having zero capacity buffering during a checkout?

The cashier would have to wait for the bagger to finish each item. Signup and view all the answers

What is a key characteristic of time sharing that distinguishes it from simple multiprogramming?

It permits simultaneous access of multiple users to a single computer system. Signup and view all the answers

What is the primary function of an operating system?

To manage a computer’s resources. Signup and view all the answers

What happens first in the sequence of interrupts when a key is pressed?

The keyboard sends an interrupt to the CPU. Signup and view all the answers

What does the CPU do after acknowledging the keyboard interrupt?

It saves the current state of the task. Signup and view all the answers

In the context of interrupts, what does the interrupt vector do?

It contains the keycode for the specific interrupt. Signup and view all the answers

What is the final step in the sequence of interrupts?

The CPU returns to the original task. Signup and view all the answers

What occurs during a supervisor call?

The operating system performs tasks requiring its authority. Signup and view all the answers

What is the role of interrupts in a computer system?

To allow the CPU to manage urgent tasks. Signup and view all the answers

Which of the following best describes how a CPU processes an interrupt from a keyboard?

It saves the state, processes the interrupt, then returns. Signup and view all the answers

What is the first step the operating system takes when a file copy command is issued?

Ask the OS to find the file. Signup and view all the answers

In which mode can applications run with limited permissions to avoid affecting critical system parts?

User Mode Signup and view all the answers

What analogy describes the OS checking permissions for accessing a file?

A librarian checking if you can borrow a book. Signup and view all the answers

What is the primary function of spooling in operating systems?

To queue documents for printing. Signup and view all the answers

Why is it important for the OS to keep programs from running in kernel mode at all times?

To prevent accidental or malicious system damage. Signup and view all the answers

What is meant by multiprogramming in the context of operating systems?

Simultaneously handling different programs by switching between them. Signup and view all the answers

What does the term 'monitor mode' refer to in operating systems?

A state where the OS has full control and hardware access. Signup and view all the answers

How does the OS ensure that the CPU is always engaged when performing multiple tasks?

By switching between actively waiting programs. Signup and view all the answers

Study Notes

Interrupts

Interrupts are signals that interrupt the CPU's current task to handle something more urgent.
They are often triggered by Input/Output (I/O) devices like keyboards, mouse or other peripherals.

Interrupt Sequence

Device Sends Interrupt - An I/O device notifies the CPU of an event, e.g., a key press.
CPU Acknowledges - The CPU pauses its current task and acknowledges the interrupt.
Device Sends Interrupt Vector - The device sends a code (interrupt vector) identifying the specific event, e.g., a keyboard keycode.
CPU Saves Current State - The CPU saves the state of its current task to restore it later.
CPU Processes the Interrupt - The CPU handles the event, e.g., displays the pressed letter on screen.
Interrupt Handled, Return to Original Task - The CPU resumes its previous task after handling the interrupt.

Supervisor Calls (System Calls)

Supervisor calls happen when a program requests the operating system to perform tasks that require privileged access, like interacting with hardware or accessing files.
OS performs tasks like:
- Checking permission
- Locating the file
- Copying the file

Execution Modes

User Mode - Programs run with limited permissions. They cannot access critical system resources directly.
Kernel Mode (Monitor Mode) - The operating system runs in this mode, allowing full access to hardware resources and system functions.

Multiprogramming

Multiprogramming allows the CPU to switch between multiple tasks quickly, ensuring it is always busy. This improves system efficiency.

Spooling

Spooling allows a device like a printer to handle jobs sequentially by storing them in a queue (the spool) while it is busy with the current job.

Time sharing allows multiple users to access the same computer system simultaneously by switching between them quickly. Each user gets a small time slice of the computer's resources, creating an illusion of individual access.

Buffering

Buffering is temporary storage for data that balances speed discrepancies between two operations.
Zero Capacity - No buffer, the faster process waits for the slower one.
Bounded Capacity - Limited buffer space, slower process has to wait if the buffer fills up.
Unbounded Capacity - Infinite buffer space, faster process can continue uninterrupted regardless of the slower process speed.

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Description

This quiz explores the concepts of interrupts and supervisor calls in computer systems. Learn how the CPU manages different tasks and responds to I/O device signals. Test your knowledge on interrupt sequences and the role of system calls in operating systems.