Linux is a Unix like operating system. It is open source and free. A user can interact with Linux either using a ‘graphical interface’ or using the ‘command line interface’.

What are core components of Linux?

1. The Programs- Set of instructions. When a program is launched, it creates processes. Program or process will be used interchangeably.

2. The Kernel-The kernel of Linux is the hub of the operating system: it allocates time and memory to programs and handles the filestore and communications in response to system calls.

3. The Shell-The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called the shell. The shell is a command line interpreter (CLI). It interprets the commands the user types in and arranges for them to be carried out.

Linux- Files and processes

Everything in Linux/Unix is either a file or a process.

Process
When you run a program, a process is created. Every process is identified by a number called process ID, given by Operating System. To check the processes you are running, execute “ps” command on the shell. It may be different at different execution of the same program.

File
A file is a sequence of data. A file could be created by users using word processors or text editors or by the program to keep the information. A program is kept in the form of a file and when it is run by the kernel, it loads as a process.
A file is generally written on the disk so that it exists even after the computer restarts. A file is identified by a name called file path. In Unix, everything is represented as file.