Pass-D-Fail
Columbia used to offer a Pass-Fail option, but this has since been superseded by the Pass-D-Fail option. Under Pass-D-Fail, you can choose one course each semester for which you'll receive a grade of either P, D, or F. If you got a P grade, Registrar will also inform you of your original grade, which you can then choose to "reveal".
The new policy is designed to encourage students to actually work for their Pass-D-Fail course. First, if you do no work as many students did under Pass-Fail, you run the risk of narrowly missing a C or C- and instead getting a D. Second, if you're doing well up to the Pass-D-Fail deadline, you might as well continue to do well for another month and get a good grade in the course as a whole.
That said, Pass-D-Fail introduces a new dilemma. If, say, you get some mediocre grade like a B or B+, do you choose to reveal it, or do you keep it hidden behind the P?