operating system vs software

operating system

noun
  • Software for controlling the allocation and use of various hardware resources (memory, CPU time, disk space, input and output devices) to tasks and remote terminals. 

software

noun
  • Encoded computer instructions, usually modifiable (unless stored in some form of unalterable memory such as ROM). 

  • Hyponyms: application software, data-oriented software, kitchen table software, on-premises software, malware, schlockware, shareware, shovelware, spyware, system software 

  • The human beings involved in warfare, as opposed to hardware such as weapons and vehicles. 

How often have the words operating system and software occurred in a corpus of books? (source: Google Ngram Viewer )