Operating system                An  operating system  ( OS ) is  system software  that manages  computer hardware  and  software  resources and provides common  services  for  computer programs . All computer programs, excluding  firmware , require an operating system to function.   Time-sharing  operating systems  schedule tasks  for efficient use of the system and may also include accounting software for cost allocation of  processor time ,  mass storage ,  printing , and other resources.   For hardware functions such as  input and output  and  memory allocation , the operating system acts as an intermediary between programs and the computer hardware, [1] [2]  although the application code is usually executed directly by the hardware and frequently makes  sys...