A system should be defined by its boundaries - the limits that identify its components, processes and interrelationships when it interfaces with another system. For example, in a 'computer system' there is a boundary for the number of bits, the memory size etc. that is responsible for different levels of accuracy on different machines (like 16-bit, 32-bit etc.). The interface in a 'computer system' may be a CUI (Character User Interface) or a GUI (Graphical User Interface).