L-1.7: System Calls in Operating system and its types in Hindi

Summary

This video script explains the concept of system calls, which are essential for transitioning from user mode to kernel mode in operating systems. It covers the necessity of system calls for accessing hardware devices and files, and categorizes them into file-related, device-related, information-related, process control, and inter-process communication system calls. The script also touches on system calls for security and protection, emphasizing their importance in operating systems.

Takeaways

• 🔒 **User Mode vs Kernel Mode**: Applications run in user mode, but to access OS functionalities, they must switch to kernel mode.
• 📲 **Purpose of System Calls**: System calls are the programmatic method to transition from user mode to kernel mode.
• 💻 **System Calls in Programming**: In languages like C, system calls (e.g., read, write, open) are used to interact with the kernel for tasks like file handling or device access.
• 🌐 **Variety in System Calls**: Different operating systems have different sets of system calls; for instance, Windows has around 700 system calls.
• 📁 **File-Related System Calls**: These are used for creating, opening, reading, and writing files, requiring kernel privileges.
• 🖥️ **Device-Related System Calls**: Necessary for accessing hardware devices like hard disks, printers, or monitors.
• 📊 **Information-Related System Calls**: Used to retrieve metadata about processes, devices, and system information like time and date.
• 🔄 **Process Control System Calls**: Facilitate process loading, execution, and control, including the creation of child processes with fork.
• 🔗 **Inter-Process Communication (IPC)**: System calls like Pipe() and Shmget() enable communication between processes.
• 🛡️ **Security and Protection**: System calls such as chmod and umask are used to manage file and system security.

Q & A

What is the primary purpose of a system call?

The primary purpose of a system call is to allow a program running in user mode to request services from the operating system's kernel, thus transitioning from user mode to kernel mode.

Why can't user mode applications directly access hardware or system resources?

User mode applications cannot directly access hardware or system resources because they do not have the necessary privileges to do so. Direct access must be mediated by the operating system's kernel through system calls to ensure security and proper resource management.

What is the difference between user mode and kernel mode?

User mode is a restricted environment where applications run, while kernel mode is a privileged mode that gives the operating system direct access to hardware and system resources. System calls are used to transition from user mode to kernel mode to perform operations that require higher privileges.

Can you provide an example of a system call in a C program?

Yes, in a C program, system calls such as 'read', 'write', 'open', 'close', and 'fork' are used to perform operations like reading from or writing to a file, opening or closing a file descriptor, or creating a child process.

How does the concept of system calls vary across different operating systems?

The concept of system calls remains the same across different operating systems, but the specific system calls available and their implementation can vary. For example, Linux has a different set of system calls compared to Windows, which has around 700 system calls.

What is the role of APIs in the context of system calls?

APIs (Application Programming Interfaces) provide a higher-level abstraction for developers, allowing them to perform operations without directly using system calls. APIs often internally call system calls to execute the required tasks.

What are file-related system calls and why are they necessary?

File-related system calls are used to perform operations on files, such as creating, opening, reading, and writing files. They are necessary because they allow user mode applications to interact with files on the disk through the kernel, which manages file access and permissions.

How do device-related system calls enable access to hardware?

Device-related system calls enable access to hardware by allowing user mode applications to request the kernel to perform operations on devices like hard disks, printers, or monitors. This is done to ensure that hardware access is controlled and secure.

What is the significance of the 'fork' system call in creating a multiprocessing environment?

The 'fork' system call is significant because it allows a process to create a child process, effectively duplicating itself. This is the foundation for multiprocessing, where multiple processes can run concurrently and perform different tasks.

What are inter-process communication (IPC) system calls and why are they used?

Inter-process communication system calls are used to allow two or more processes to communicate with each other. They are used for data exchange and synchronization between processes, and can involve mechanisms like pipes, shared memory, or message queues.

Can you explain the role of 'getpid' and 'getppid' system calls?

Yes, 'getpid' is used to obtain the process ID of the current process, while 'getppid' retrieves the process ID of the parent process. These system calls provide information related to process identification, which can be useful for process management and tracking.