#CMS lacks I/O redirection (Unix-like facilities have been added to #Theos); so CMS’s #EXEC has an unusual workaround that Theos retained: the #STACK and BEGSTACK keywords.

STACK (actually, &STACK, because all EXEC keywords and variables are prefixed with an ampersand) places a single line of text on a stack, which has precedence overthe keyboard puffer. When an EXEC script or other Theos program requests data from the keyboard, data placed by the STACK directive is read instead.

STACK, as its name suggests, is cumulative. For the really big jobs, a block of text can be surrounded by BEGSTACK and END keywords. An entire session with an application can be driven in this way. (t y)