Operating systems

1. Mac

1.1. Made by Apple

1.2. First introduced in1984

1.3. Recent versions

1.3.1. Mac OSX 10.9

1.3.2. Mac OSX 10.10

1.3.3. Mac OSX 10.11

2. General info

2.1. Essential system software

2.2. Intermediary between hardware and software

2.3. Found on many devices that contain a computer

3. Windows

3.1. Made by Microsoft

3.2. First introduced in 1983

3.3. Recent versions

3.3.1. Windows 7

3.3.2. Windows 8

3.3.3. Windows 10

4. Linux

4.1. Based on Unix

4.2. First introduced in 1991

4.3. Made by the community (open source)

4.3.1. Released by Linus Torvalds