Jawaharlal Nehru Technological University Hyderabad B.Tech IV REAL-TIME SYSTEMS Previous Question Paper (July/August - 2022 - R16)

In UNIX, everything is treated as a file. The primary types are:

• Ordinary Files: These contain user data, such as text, source code, or binary executables. They are the most common file type.
• Directory Files: These act as containers that store lists of filenames and their corresponding inode numbers, providing the hierarchical structure of the file system.
• Character Device Files: These provide a raw, unbuffered interface to hardware devices that process data as a stream of characters, such as terminals or serial ports.
• Block Device Files: These provide a buffered interface to hardware devices that store data in fixed-size blocks, such as hard drives or USB storage.
• Symbolic Links: These are special files that act as pointers or shortcuts to another file or directory, allowing multiple names for the same data.
• Named Pipes (FIFOs): These are used for inter-process communication, allowing processes to exchange data in a first-in, first-out manner.
• Sockets: These are specialized files used for network communication between processes, potentially across different machines.

Process control in UNIX involves managing the lifecycle, execution, and state of processes using specific system calls and commands:

• fork(): This system call creates a new process (child) by duplicating the calling process (parent). The child receives a unique process ID (PID).
• exec(): This family of functions replaces the current process image with a new program, allowing a process to execute a different binary while retaining its PID.
• wait(): This command allows a parent process to pause execution until one of its child processes terminates, preventing the creation of zombie processes.
• exit(): This terminates the calling process, releasing its resources and notifying the parent process of its completion status.
• kill(): This command sends a signal (such as SIGTERM or SIGKILL) to a process, typically used to request or force the termination of a running process.
• ps and top: These commands are used to monitor the status, resource usage, and hierarchy of currently active processes in the system.