L-1.10: User mode and Kernel mode in operating system in hindi

Summary

In this educational video, the presenter explores the concepts of user mode and kernel mode in operating systems. They explain that user mode is where applications run, while kernel mode handles core system functionalities and hardware control. The video uses a relatable bank analogy to illustrate the necessity of system calls for user processes to access hardware. It emphasizes the importance of this dual-mode operation for resource management and security, suggesting its relevance in competitive exams.

Takeaways

• 💻 **User Mode Definition**: User mode refers to the state where users interact with applications on their computers.
• 🛠️ **Kernel Mode Definition**: Kernel mode is where the core functionalities of the operating system, major drivers, and hardware interactions occur.
• 🔄 **Mode Switching**: The processor switches between user mode and kernel mode to perform different tasks.
• 📝 **Example with Text Editor**: When using a text editor to write a C program that reads from and writes to a file, the process involves a system call.
• 📖 **System Call Usage**: The 'read' system call is used to access the file on the hard disk, which is managed by the kernel.
• 🚀 **Transition to Kernel Mode**: Upon executing a system call like 'read()', the system transitions from user mode to kernel mode.
• 🔒 **Hardware Access Control**: Users cannot directly access hardware; they must go through the kernel for such operations.
• 🏦 **Bank Analogy**: The script uses a bank analogy to explain the separation between user mode and kernel mode, emphasizing the need for system calls to access hardware.
• 🔙 **Return to User Mode**: After the system call is executed, the system returns to user mode, completing the task without direct hardware access.
• 🔁 **Dual Mode Operation**: The operating system constantly switches between user mode and kernel mode to manage resources and ensure system integrity.
• 📈 **Relevance in Exams**: The concept of user mode vs kernel mode is important for competitive exams and understanding threads in operating systems.

Q & A

What is user mode in the context of operating systems?

User mode refers to the state in which a user interacts with applications on their computer. It is the default mode when using applications, and it does not have direct access to hardware components.

What is kernel mode and how does it differ from user mode?

Kernel mode is a privileged mode in an operating system where core functionalities, major drivers, and hardware controls are executed. It differs from user mode by having direct access to hardware and system resources, which user mode lacks.

Why does a processor switch between user mode and kernel mode?

A processor switches between user mode and kernel mode to manage resources and ensure system security. This prevents user applications from directly accessing hardware, which could lead to system instability or security issues.

What is a system call and how is it used in the context of user mode and kernel mode?

A system call is a mechanism that allows user mode applications to request services from the kernel. It is used to access hardware indirectly, ensuring that user applications do not directly manipulate hardware components.

Can you explain the example given in the script about using a text editor in Linux?

In the example, when a user opens a text editor to write a C program, they are in user mode. If the program needs to read or write a file, a system call (like 'read()') is used to transition to kernel mode, where the operation is performed, and then the system returns to user mode.

What happens when a system call is made to read data from a file?

When a system call to read data from a file is made, the processor transitions from user mode to kernel mode, where the kernel reads the data from the hard disk and then returns control back to the user mode application.

How is the transition from user mode to kernel mode represented in terms of mode bits?

The transition from user mode to kernel mode is represented by a change in mode bits. In the script, it's mentioned that the mode bit changes from 1 (user mode) to 0 (kernel mode) when a system call is made.

What is the real-life analogy used in the script to explain the concept of user mode and kernel mode?

The script uses the analogy of a bank where the user (customer) is in user mode and the bank clerks are in kernel mode. The customer must request services through a teller, similar to how a user application makes system calls to access kernel services.

Why is it important for the operating system to manage resources and govern access to hardware?

Managing resources and governing access to hardware is crucial for the operating system to maintain system stability, prevent unauthorized access, and ensure that applications do not interfere with each other or the system's core functions.

How does the concept of user mode and kernel mode apply to other processes like printing output to a monitor?

When a user wants to print output to a monitor, a system call is generated to transition to kernel mode, where the operating system handles the output to the monitor. This ensures that user applications do not directly control hardware like monitors.

What is the significance of understanding user mode and kernel mode in competitive exams?

Understanding user mode and kernel mode is significant in competitive exams because it tests the candidate's knowledge of operating system fundamentals, which is a core concept in computer science and essential for many technical roles.

Outlines

00:00

💻 Understanding User Mode vs Kernel Mode

This paragraph introduces the concepts of user mode and kernel mode in operating systems. User mode refers to the state where regular applications run, and users interact with the system without direct access to hardware. Kernel mode, on the other hand, is the privileged state where the operating system's core functionalities and drivers execute. The processor switches between these modes to manage resources and ensure system stability. An example using a Linux text editor is provided to illustrate how a user process, like a C program, needs to make a system call to read or write to a file on the hard disk, which is managed by the kernel. The paragraph explains the transition from user mode (mode bit 1) to kernel mode (mode bit 0) through a system call and the importance of this dual-mode operation for resource management and security.

05:04

🔄 Switching Between User and Kernel Modes

The second paragraph elaborates on the continuous switching between user mode and kernel mode that occurs during normal operation. It explains that most applications run in user mode, but when a task requires hardware interaction, such as printing output to a monitor, a system call is made, causing a switch to kernel mode. The paragraph uses the analogy of a bank to illustrate the separation between user mode and kernel mode, emphasizing that users cannot access hardware directly without going through the kernel. It concludes by highlighting the importance of this dual-mode operation for maintaining system integrity and preventing unauthorized hardware access, and it encourages viewers to engage with the video by liking, sharing, and subscribing.

Keywords

💡User Mode

User mode refers to the state in which a computer operates when it is running applications or tasks initiated by a user. In the video, the user mode is exemplified by the act of using a text editor to write a C program. It's the default mode when users interact with applications on their computers. The video emphasizes that user mode is limited in terms of accessing system hardware directly, which is a crucial aspect of maintaining system security and stability.

💡Kernel Mode

Kernel mode is the privileged mode of operation in an operating system where the processor executes code with the highest level of access to system resources. The video explains that all core functionalities, major drivers, and hardware operations are managed in kernel mode. It's the mode the system enters when performing tasks that require direct hardware access, such as reading from or writing to a hard disk, which is illustrated in the video through the example of a C program needing to read and write files.

💡System Call

A system call is a request from a program for a service offered by the kernel. In the video, the concept of system calls is central to the discussion of how user mode applications interact with the kernel mode to perform operations that require higher privileges. The 'read' system call is used as an example to show how a user mode application requests the kernel to read data from a file on the hard disk.

💡Processor Modes

Processor modes refer to the different states a processor can be in, which dictate the level of access to system resources. The video discusses the switching between user mode and kernel mode as the processor handles different tasks. This dual-mode operation is essential for protecting system integrity and ensuring that user applications do not inadvertently or maliciously harm the system.

💡Hardware Access

Hardware access in the context of the video refers to the ability of a program or process to interact with the physical components of a computer, such as the hard disk. The video explains that user mode applications cannot directly access hardware; they must go through the kernel via system calls. This is illustrated by the necessity of a system call when a user mode application needs to read from or write to a file on the hard disk.

💡Operating System

The operating system is the software that manages computer hardware, software resources, and provides services to computer programs. In the video, the operating system is likened to a bank that manages resources and governs access to hardware, ensuring that user mode applications do not directly interfere with hardware operations, which is a critical function for maintaining system security and performance.

💡API (Application Programming Interface)

APIs are sets of routines, protocols, and tools for building software applications. In the video, the text editor is mentioned as an application that uses APIs to allow users to write programs and codes. APIs provide a way for applications to request services from the operating system without needing to access the hardware directly.

💡Trap

A trap in computer terminology is a type of interrupt that is triggered by the execution of an instruction. In the video, a trap is mentioned as the mechanism that shifts the processor from user mode to kernel mode when a system call is made, such as when a program needs to read from a file. This transition is crucial for the security and proper functioning of the system.

💡Dual Mode

Dual mode refers to the capability of a processor to switch between user mode and kernel mode. The video emphasizes the importance of this feature for the proper functioning of an operating system, as it allows for the secure execution of tasks that require different levels of access to system resources.

💡Mode Bit

The mode bit is a part of the processor's status register that indicates the current mode of operation. In the video, the mode bit is used to illustrate the change in processor state when switching between user mode (1) and kernel mode (0). This bit change is a fundamental aspect of the processor's operation in managing access to system resources.

Highlights

User mode is the default mode when using applications on a computer.

Kernel mode handles core functionalities, major drivers, and hardware interactions.

Processors switch between user mode and kernel mode to manage tasks.

An example of using a text editor in Linux to write a C program illustrates user mode.

Accessing hardware, like reading from a file on a hard disk, requires kernel mode.

System calls are used to access kernel mode and interact with hardware.

The 'read' system call is used to access data from a file in kernel mode.

Kernel mode is entered by generating an interrupt or trap from user mode.

Executing a system call in kernel mode allows reading data from the hard disk.

After system call execution, the processor returns to user mode.

A real-life analogy compares user mode to a bank customer and kernel mode to bank staff.

Direct hardware access by users is prohibited to prevent system instability.

The operating system's responsibility is to manage and govern system resources.

User mode is used for everyday applications like listening to music or using Microsoft Office.

Kernel mode is required for tasks that involve hardware, like printing output to a monitor.

The concept of user mode and kernel mode is important for understanding system operations.

The dual mode switching is crucial for system security and resource management.

Understanding user mode vs kernel mode is beneficial for competitive exams.

The video will also cover threads and their relation to user and kernel mode.

Transcripts

Hello friends, Welcome to Gate Smashers

In this video we are going to discuss user mode vs kernel mode in operating system

So what does user mode means? As the name says, user mode

Here we are talking about user, like we are users,

we turns on over laptop and PCs and we use some application there,

so whenever we are using some application, then by default we are in the user mode

But all core functionalities of operating system, all major drivers,

all works and executes in the kernal mode

And the processor keeps switching between user mode and kernel mode

Now let me tell you with a very simple example Let's say if I'm using a Linux operating system

And in lunix operating system I opened text editor

means text editor is an application where you can write programs and codes

So I opened text editor, means I'm using API and I'm writing a C program through it

Now when I wrote that program, Let's say it is written in that program that you have to read a file

and write some data into a file, means I have to read some file and update some value in it

So here you have to focus that this file is in the hard disk

and hard disk is a hard ware component of our system

And all the hardware are in control of kernel, operating system

So user can't access the hardware directly, it needs kernel

So when I started executing the program, so here I wrote user process executing

User process means that C program is executing and now I have to read some file in that program

So reading that file means now I have to use system call here

System call is a way to access kernel,

means we have to access hardware through kernel, System call is a way to access it

so which system call will get used here by default?... Read system call

Read system call means that I have to read data from some particular file

So when it'll be get system call Which system call??... Read()

there my system will go in which mode? It'll go in kernel mode

And kernel mode's bit is zero

Means first we were in Mode 1,

The moment we came in read system call from Mode1 there generates an interrupt or a trap

A trap will generate... trap means you got shifted from other mode to kernal mode

The moment you got shifted in this mode, you mode bit changed from 1 to 0

Now what you should do is... execute the system call

Means you are reading the data, means whatever file you wanted to read in the hard disk

You'll read the data from the hard disk and after reading the data, you'll use write system call there

You read the data and wrote it also now you'll again go back to your user mode

Because we as user, we are just working in the user mode,

so I have to come back from system call to our user mode

So here, again mode bit will change from 0 to 1

So If I would relate it with real life example, so let's say if I goes to some bank,

Let's take a bank, bank is acting as a computer

Now if I want to withdraw money from the bank, then I'm user mode so I went to the bank

And working in user node, but those clerk and PO sitting behind the window they can work in kernel mode

Can you do this like you went to the bank and directly near their window

and took the money from the back side... NO, this will never going to happen

Because you are user mode and it's kernel mode, you can't access directly

If you'll go to the bank and will just take out the money from the drawer,

then there'll be no function of kernel mode, you are accessing the hardware directly

So this can create a very big problem,

you are overwriting directly and taking all hardware in your control

And this is the major responsibility of operating system, to manage the resources

And to govern the resources.... so you would fill the form

and give it to them through the little window and they'll give you the money,

so that mode where you are going from 1 to 0

and when you got the money then you are going from 0 to 1

So you got the money back means your work is done and process is executed

then you can leave from there, So we are using the same logic here in the system also

Whatever application we are using by default, whether we are listening songs or watching a video

Whether you are working in Microsoft office No matter what application you are using

That application works in user mode by default

and your processor keeps switching between both of these modes

But when in some process,

If you want to write a C program where you have to do 2+2 = 4

So you don't need kernel to do 2+2 = 4

But if you want that output 4 to get printed on the monitor

Then you writes print + F Then what is print + F??...

Then print + f means you want to print some output on the monitor

So monitor is in whose hands?... In operating system's hands

Then system call will get generated there

and that system call will print the value on the monitor

This way our system keeps changing between user mode and kernal mode

It's called dual mode so it's very important otherwise there'll be so much problem

You are accessing the hardware and system, so we are working on user mode

Operating system works on kernel mode and switching keeps happening here

Although this is a theoretical topic but many times theory questions comes from it in competitive exams

And after this we'll discuss about threads so in threads also the concept that we use

So this is all about the difference between user mode and kernel mode

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Thank You!