# Introduction to Information Technology/Operating Systems
## Major Operating Systems
### Microsoft Windows
### Apple OS

History
The Apple operating system currently known as OS X originated at a company called NeXT after Steve Jobs left apple. The original system, known as NeXTSTEP, and soon after OPENSTEP and was launched in 1989. When Apple purchased NeXT and re-hired Steve Jobs in 1996, they used OPENSTEP as the basis for the first Apple OS. Steve Jobs begin to head the transformation of a more programmer based OPENSTEP into a more, home user and business friendly version under a project called Rhapsody and then renamed Apple OS X. Apple released the first version of OS X for consumers in 2001. Since its release, OS X has gone through several versions, most of which named after big cats such as Lion and Snow Leopard. Since the release of the iPhone Apple has made OS X more compatible with iOS, the iPhone and iPad OS. OS X has also received many of its design aspects from iOS. Today OS X users make up over 10% of the Computer using population.

### Linux

Linux is the best-known and most-used open source operating system. As an operating system, Linux is software that sits underneath all of the other software on a computer, receiving requests from those programs and relaying these requests to the computer's hardware.

#### Distributions
##### Ubuntu

Known by many as the most user friendly kernel of Linux, Ubuntu is a Debian-based operating system used for personal, smartphone, and corporate use. Ubuntu finds its popularity from its user friendly UI know as Unity. Ubuntu is currently used and distributed for free by Canonical Ltd.

##### RedHat

Red Hat, Inc. is an American multinational software company providing open-source software products to the enterprise community. ... Red Hat has become associated to a large extent with its enterprise operating system Red Hat Enterprise Linux and with the acquisition of open-source enterprise middleware vendor JBoss.

## File Systems

File Allocation Table (FAT):
A file allocation table is a type of file system that the operating system maintains on a storage device. The FAT provides a map of the clusters that contain each file. It works by splitting a file disk into different clusters. There are two types of clusters on a FAT file:
* Data Clusters: hold the file contents
* Directory Clusters: contain metadata for all files (file names, timestamps and starting cluster for the file)
After each cluster is given a unique ID number, the FAT file uses a table to track what part of a file was stored in each cluster.
New Technology File System
New Technology File System or NTFS is a common journaling file system used for Microsoft Windows. It can recover disk errors which can be read. NTFS is necessary for Windows to perform improved reliability, to support a large amount of spaces, and to provide data encryption for sensitive files. NTFS can store files in a disk space more than 16 terabytes (TB). Unicode character set is supported and you can create a long name for storing files in a NTFS disk space.

## Giving Commands to an Operating System

ls is the common format that all Linux commands follow. "ls" stands for "list" because when you type ls in the Linux command line, your're asking the computer to list something. A regular ls command will list the basic files and directories. A ls command with a - and a letter after it will list other things depending on the letter. For instance " ls -a" will list all the files in the directories.