9.6. What an Implementation is Allowed to “Ignore” In order to make the REXX language implementable on as many machines as possible, the REXX standard allow implementation to ignore certain features. The existence of these features are recommended, but not required. These features are: [Floating point numbers] Are not required; integers will suffice. If floating points are not supported, numbers can have not fractional or exponential part. And the normal division will not be available, i.e. the operator “/” will not be present. Use integer division instead. [File operations] Are defined in REXX, but an implementation seems to be allowed to differ in just about any file operation feature.