Computer Operating System

A Computer Operating system is a set of programs which performs a set of tasks that include:

• Peripheral control
• Job loading
• Job execution
• Multiprogramming
• Time sharing
• Batch processing
• Time sharing
• File management

The computer operating system acts as the interface between man and machine. A Computer Operating system has become a necessity owing to the complex nature of hardware and application programs.

Examples of Operating Systems

There exist many computer operating systems today. In this article, we look at two computer operating systems and the important commands to use in its applications.

1. Disk Operating Systems (DOS)
2. Linux

1. Disk Operating System

As a command-based Operating system of the 80s to late 90s, Disk operating system (D.O.S) runs from the hard disk drive. Unlike most predecessor operating systems regarded as user friendly, easier to use because of graphical user interface (GUI), DOS is a command-based and you need to know the commands to operate.

DOS Commands

Command	Description
DIR	Directory Lists all files in the current directory
Dir/P	Displays one page at a time
CLS	Clear Screen
Time	Displays or changes system time
Date	Displays or changes system date
CD	Change Directory To go into a directory, you press CD (space) To get out of a directory you press CD (space)
Tree	Used to display the directory structure graphically Type Tree/F to see the true structure and all files inside the structure
Ren	Used to rename a file Type Ren space old file name. ext space new filename.exe
Ver	Used to display the Ms Dos version
Label	Displays change or delete the volume label in your disk. Type label space a:
Type	Shows the content of a text file Text file - (files saved in ASCII code, can be read by use of type command) e.g Doc,  Bat, Txt and Prn Binary file- ( is a file saved in machine code using the type command. Displays control characters.
SCANDISK	Used to scan and correct disk errors Type scandisk (space) a:
Move	Used to display one screen at a time Type space Readme.txt: more
Wild cards	Used to denote any one character ?
Asteriks	Used to denote a combination of characters * e.g., any name with an extension *.*

2. Linux

Linux is an operating system based on Linux kernel. Common Linux distributions include Ubuntu, Fedora and Debian Linux.

Commercial and popular uptake

Linux operating systems is a popular OS used in computing including embedded systems and supercomputers. Linux operating system is greatly used in Smartphone mobile devices and wearable consumer market. Through immergence of Valve, Linux operating system is used in Linux gaming

Hardware support

The Linux kernel is a port OS kernel that available from a wide range of devices. It can run on different types of computer architecture. Also available are other special distributions and kernel for less mainstream architectures including ELKS and fork. They can run on systems in the absence of a memory management unit

How to add users in Linux

The major tool used to add new users on Linux system is useradd command. It enables one to create another user account and be able to configure the users $HOME directory structure. By combining both the system default settings and command line parameters, the useradd creates a new user account. To view the system default values on Linux distribution, one needs to use the command useradd and chose option D To be able to set up useradd command, the default settings /etc/default/useradd file is used. For additional security settings, additional definitions are in /etc/login.defs file. If you need to change the default security behavior, you can do so by editing the files. Here is a list of some default values that are used by useradd command when you do not explicitly specify them on the command line at the time of creating a new user on the Linux system.

• A new user will be assigned to a group ID 100.
• The directory /home/username $HOME is created for a new user.

Account is terminated when the password expires.

• There will not be an expiry date set
• The default shell for the new account will be the bash shell

The /etc/skel directory contents are copied to the user's $HOME directory.

• The Linux system will create in the mail directory a user account to receive mail.

Creating a $HOME Directory

Using the useradd command, an administrator can create a $HOME default directory configuration and the directory for the new user’s $HOME is created using the configuration as a template. This makes it easier to add system default files automatically to every new user’s $HOME directory. The default startup files for the login shell environment are zsh, bash,fsh e.t.c. New user created results in the system to automatically copy default files into their $HOME directory. You  view this by creating another new user account within the systems default settings, and checking the new user’s $HOME directory files. By default, the useradd program doesn't create a $HOME directory in most Linux distributions. The -m command line option instructs the system to do so and can be edited in the /etc/login.defs file. Use the useradd command-line to modify a default value or behavior at the time of creating a new user.

Linux commands

Command	Description
d dir_name	Specifies a name different from login name credential for the HOME directory.
m	Creates the user’s HOME directory.
M	Disables the creation of a user's HOME directory
N	Not to duplicate or create a group with the same name as the user
p pass	It’s for encrypted password of a new account.
U	Helps one create a group with the same name as the user.
s SHELL	For Login shell of the new account.
r	Helps in creating a system account.

You can check for more information for useradd command help (useradd --help) or use manual - man useradd for more options you can interact with. Kindly use the comment section to share your thoughts on this topic and tell us about your experience with other types of operating systems. Your engagement and positive criticism help us to keep writing and sharing our knowledge in this diverse area.

The writer is a Business Management and Information Technology student from the prestigious Kabarak University.

Quote:

"If future generations are to remember us more with gratitude than sorrow, we must achieve more than just the miracles of technology. We must also leave them a glimpse of the world as it was created, not just as it looked when we got through with it". -Lyndon B. Johnson, Former President of the United States of America