OpenOS is a basic operating system available in OpenComputers. It is required to boot up a computer for the first time, and can be crafted by placing an empty floppy disk and an OpenComputers manual inside a crafting table.
Once crafted, the floppy disk can be placed inside a disk drive connected to a correctly configured computer system, which will allow the computer to boot up OpenOS. Once booted, it is advisable to install OpenOS to an empty hard drive, foregoing the need for a floppy disk and to gain access to a read-write file system (the OpenOS floppy disk and other "loot" disks are read-only). A tier 3 computer case does not require a disk drive, as it has a slot built in for the floppy disk.
OpenOS can be installed by simply running install, and following the on-screen prompts to complete the installation. The floppy disk may be removed once the system has been rebooted. OpenOS can be installed on all devices except drones and microcontrollers (both of which require manually programming an EEPROM to provide functionality, because they have no built in file system).
OpenOS has many built in functions, the most useful of them is the lua command, which opens up a Lua interpreter. This is a good testing space for trying out various commands, and experimenting with component API, before writing the commands into a .lua script. Take note of the information displayed when starting the interpreter, it will tell you how to show results of the commands you enter, and how to exit it.
For more information on programming, refer to the Lua Programming page. To run Lua scripts, simply type in the name of the file and hit enter (for example, script.lua can be run by typing the script command in the terminal).