Ans:

• The group ID of the new file can be the effective group ID of the process
• The group ID of the new file can be the group ID of the directory in which the file is being created.

Ans:

• Regular file
• Directory file
• Character special file
• Block special file
• FIFO
• Symbolic link
• Socket

Ans: A program is a executable file residing in a disk file. An executing instance of a program is called a process. Every UNIX process has a unique numeric identifier called the process ID. The process ID is always a non negative integer.

Ans: A directory is a file that contains directory entries. The directory entry containing a file name along with structure of information describing the attributes of the file. The names in a directory are called filename. The only two characters that cannot appear in a file name are / and null character.

Ans: UNIX is the most popular operating system on multi-user systems. This operating system originated as a single-user system. It started off on a cast-off DEC PDP-7 at Bell laboratories in 1969. Ken Thompson, with ideas and help from Dennis Ritchie, and others, wrote a small, general-purpose operating system.

Ans: message queue Message queue is a linked list of messages. It is used to make a communication between the related or unrelated processes.

Ans: A session is a collection of one or more process groups. A process establishes a new session by calling setsid function. This function returns process group id if OK.

Ans: Pwd.

Ans:

• Password protection
• File permissions
• Encryption.

Ans: Kernel is core part of UNIX o/s. It is a group of hundreds of system calls.