operating software
There is someone selling one of these on ebay, the instructions are with it, just a thought.
The "Operating System" or OS
Fan not working
operating sytem
Standard Operating Procedures (SOPs)
put the disk in, and follow instructions.
Standard Operating Procedures
An operating or maintenance instruction manual.
Computer
Disk Operating System -DOS
Basically, any operating system is simply instructions written in code the computer understands.