Chief information officer (CIO), chief digital information officer (CDIO) or information technology (IT) director, is a job title commonly given to the most senior executive in an enterprise responsible for the information technology and computer systems that support enterprise goals.
CIOs manage a business’s IT systems and functions, creates and delivers strategies and policies, and places great emphasis on internal customers.
A chief technology officer (CTO), sometimes known as a chief technical officer, is an executive-level position in a company or other entity whose occupation is focused on scientific and technological issues within an organization
CTOs place emphasis on the external customers to the organization and focus on how different technology can make the company more profitable.
The COO is responsible for the daily operation of the company, and routinely reports to the highest ranking executive, usually the chief executive officer (CEO). The COO is usually the second in command at the firm, especially if the highest ranking executive is the Chairman and CEO.
As DevOps is closing the gap between several disciplines, e.g. Development, Operations, Quality Assurance one could argue that the CIO is accountable for DevOps as all these parties are internal customers. However, as a CTO is also focused on the outside world, one could also say that the CTO is accountable as he or she could implement DevOps because he or she heard in the outside world that this discipline was beneficial for some companies.