Explanation: Unix is an operating system developed in the early 1970’s at Bell Labs by Dennis Ritchie, Ken Thompson, and others. It is a multiuser, multitasking and timesharing operating system. The power of Unix is derived from its commands and their multiple options.

Explanation: The UNIX shell is both an interpreter and scripting language. We can also say that shell can be interactive or non-interactive. When we log in to our system, interactive shell presents a prompt and wait for our requests while a non-interactive shell is managed by an interactive shell while executing a shell script.

Explanation: UNIX was originally written in Assembly language but Dennis Ritchie and Ken Thompson wanted an operating system which could run on more than one type of hardware. So in 1973, they rewrote the whole operating system in C language due to which one of the strongest features i.e. portability was added to the operating system.

Explanation: It doesn’t matter what kind of work we are doing on a UNIX system, we always need an editor to edit some system files or ordinary files. For this purpose, vi editor is used in UNIX. Currently, vim (vi improved) is an improved version which is supported by LINUX systems.

Explanation: The kernel is the heart of the operating system while the shell is the utility which processes our requests. While system calls are a handful of functions which are used to interact with the kernel and make available the services provided by the operating system. A Graphical user interface (GUI) is available in UNIX, but the traditional UNIX interface is the command line only.

Explanation: The kernel is the core of the operating system. It is a collection of routines written in C which directly communicates with the hardware. User programs that need to interact with the hardware access the services of the kernel. There is only one kernel running on a system, unlike shells which can be multiple.

Explanation: UNIX provides us with a facility of man command, which is used for getting documentation of any command. For example, to seek help on wc command simply type man wc. This will simply display all the possible operations, options, description, synopsis of wc command. The POSIX specification requires only one available option with man command i.e. -k, which prints a one-line description of the command. whatis command is also available on many UNIX systems which also displays a one-line description of the command. man -f emulates the behavior of whatis command.

Explanation: Since UNIX is a multiuser system, it requires a password from every user who wants to log in to the system to help ensure that all the data and files of the user are secure from hackers and errant users. A user can simply change his/her login password by using the passwd command. Simply type this command on the terminal and then enter the old password, which after successful verification would allow the user to input a new password for his login.

Explanation: To delete all files in a directory, use (*) with rm command. It acts as a meta-character and delete all files without displaying any message on the terminal. So use this command cautiously.