Actually I think the "ve" comes from some math notation when illustrating +/- values.

"+ve" is shorthand for "positive". (label shown on the + branch of a +/- value)

"-ve" is shorthand for "negative". (label shown on the - branch of a +/- value)

In this book I don't think you'll see any "ve" in the code section, just as an abbreviation for "positive" and "negative" on illustrations.

- Michael