Chapter 2 Flashcards
What is single user system
Such a system that allows single to operate at a time. It means there can be multiple users but only one user can operate it at a time.
What are batch systems
Batch processing is the execution of a series of programs (“jobs”) on a computer without manual intervention. Jobs are set up so they can be run to completion without human interaction.
What are multi programmed system
Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them.
What is time sharing system
It is interactive, multi-user, multi-process system. It has online file system. It is real time system. Linux is also its example.
What are 2 types of real time system
- Hard real time system (When given input, output must be produce)
- Soft real time system (e.g. virtual reality, sign boards) (When given input, output should be given but if there is not output then there should not be catastrophic failure)
Where we keep data in real time system
in ROM or RAM. Not on disk
What are interrupts
An event generated by a device in a computer to get attention of the CPU
What is trap
An event generated by the CPU itself as it executes a program. CPU send message for example in some alarming situation like division by zero.
What is signal
An event generated by a user
In what situation System saves CPU state
Trap Or Interrupt
Interrupt
Does signal also called soft interrupt
Yes
What is ISR and TSR
In case of interrupt or trap, the CPU invokes a piece of code in the OS to service it, known as interrupt service routine (ISR) or trap service routine (TSR).
What are 3 possible actions in case of signal
1- Default action as defined by OS
2- Ignore signal
3- Programmed specified action
What is dual mode operation
There are 2 modes
1. user mode: executes on behalf of a user
2. monitor mode: execution done on behalf of OS.
When fault occurs CPU switches to monitor mode.
What are privileged instructions
Privileged instructions can only run in monitor mode by default. Sometimes CPU allows those instructions to run which are not allowed to execute in user mode which causes problem.
