Week 2 Flashcards
What is the dual mode of operation
The dual mode operations is a software in the operating systems used to protect the operating systems from illegal users.
This is accomplished by designating some of the system instruction as privileged instructions
Example of privileged instruction
Command to switch to user mode.
monitoring I/O,
controlling timers
handling interruptions
Modes of operating system
User mode
Kernel mode
What is the mode bit of the user mode and kernel mode
user mode: 1
kernel mode : 0
Describe user mode
DMAIR
Definition: User mode is a restricted mode, which the application programs are executing and starts.
Modes: User mode is considered as the slave mode or the restricted mode
Address space: In user mode, a process gets its own address space.
Interruption: In user mode, if an interrupt occurs, only one process fails.
Restrictions: In user mode, there are restrictions to access kernel programs. Cannot access them directly.
Describe Kernel Mode
DMAIR
Definition: Kernel mode is the privileged mode which the computer enters when accessing hardware resources. It is the core of the OS and has complete control over everything in the system.
Modes: Kernel mode is the system mode, master mode or the privileged mode.
Address space: In user mode, a process gets a single address space.
Interruptions: If an interrupt occurs, the whole operating system might fail.
Restrictions: Both user programs and kernel program can access.
What is system call
System call is executed when a user process becomes a kernel process
What are the function of a kernel
Access computer resource: It acts as a bridge between user and the resources of the system.
Resource management: It is the duty of a kernel to efficiently share the resources between various process
Memory management: It is the job of the kernel to allocate and deallocate memory space for every each process.
Device management: The peripheral devices connected in the system are used by the processes. So, the allocation of these device is managed by the kernel.
Mention Kernel Design approaches
Monolithic kernels
Microkernels
Hybrid kernels
Nanokernels
Exokernels
Mulitkernels
Describe Monolithic kernel
An operating system architecture where the entire operating system is working in kernel space.
Features of monolithic systems
Simple structure:
Works for smaller task:
Communication between components:
Fast operating system:
Advantages of monolithic kernel
The execution of the monolithic kernel is quite fast as the services such as memory management are implemented under the same address space
- A process runs completely in a single address space
- It is a static single binary file.
Disadvantages of monlithic kernel
If any service fails in the monolithic kernel, it leads to failure of the entire system.
The entire OS needs to be modified by the user to add any new service.
Describe microkernel
This is a software or code which contains the required minimum amount of functions, data and features to implement an operating system. it only contain the core functionalities of the system.
The minimum functionalites are:
Memory management
Processor scheduling
Inter-process communication
