'Our neo-Piagetian perspective leads us to view the curriculum for programming as comprising two dimensions. On one dimension are the nuts and bolts of how programming languages work. That dimension is emphasised in today’s classroom. The other and more neglected dimension comprises the skills for reasoning about programs, sometimes referred to as the notional machine (du Boulay, 1989), but which we think of in neo-Piagetian terms. This dimension is often not explicitly taught, especially in the first few weeks learning to program. We believe that, with every increment along the “nuts and bolts” dimension (i.e. with every new programming construct taught), all the neo-Piagetian stages of reasoning need to be explicitly reprised.'