Similar (but opposite ?!) to Reverse Polish Notation, in that operators act on the next two expressions (for binary operators).

Eg 5 + (6 * 7) is expressed in prefix notation as

  • 5 * 6 7

However, as RPN uses a "stack" of intermediate values it is easier to implement as when you parse an operator you already have your operands available.

LISP is probably the best known language to use prefix notation.