Lesson 1: Introduction to Unix:
UNIX is a multi-user, multi-tasking operating system, thus UNIX supports multiple users, each running mutiple processes simultaneously.
UNIX operating system is made up of 3 parts; (1) Kernel (2) Shell (3) Files and Processes.
(1) Kernel:
The kernel of UNIX is the center of the operating system. It allocated time and memory to programs. The Kernel allows system calls request different services such as file open File: open close, read, write, link, or execute a file;
(2) 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
(3) Files and Processes:
Everything in UNIX is either a file or a process. A process is an executing program identified by a unique PID .
Unix organized information into files, Every directory and file is listed in its parent directory. A directory is a file that contains a table listing the files contained within it.
An inode is a special file designed to be read by the kernel to learn the information about each file. It specifies the permissions on the file, ownership, date of creation etc.
In Unix all files are grouped together in a hierarchical structure of directories where the top of the directory is called root.
NB: UNIX is case sensitive, so you must type lower case or upper case
exactly as indicated for commands and filenames.
There are numerous version of Unix (HP, SOLARIS, LINUX)
Telnet is a program that allows you to connect your PC to a UNIX
computer through the network and control programs on the UNIX computer.
