A variable which is only referred to once in a piece of code, probably Because of a programming mistake. To Be useful, a variable must Be set and read from, in that order. If it is only referred to once then it cannot Be both set and read. There are various exceptions. C-like {assignment operators}, e.g. "x += y", read and set x and return its new value (they are abbreviations for "x = x+y", etc). A functionargument may Be passed only for the sake of uniformity or to support future enhancements. A good compiler or a syntax checker like lint should report singleton variables but also allow specific instances to Be marked as deliBerate by the programmer. (1997-12-20)