The PhD program is intended for full-time on-campus students. Applicants who expect to spend any or all of their time during the academic years employed outside the department are strongly discouraged. Summer internships elsewhere, however, are usually acceptable and often encouraged. Students fully funded by Columbia are not permitted to hold outside positions during the periods of their appointment; very limited consulting may be permitted only in cases where the student is otherwise making satisfactory progress.
If a self-funded or employer-funded applicant must work externally during the early portion of the PhD program, it is strongly recommended that the applicant enroll instead in either the terminal Master of Science or professional Computer Systems Engineer degree program. The faculty advisors of such MS and CSE students may petition the PhD Chair for permission for such students to undertake some of the doctoral program requirements prior to formal enrollment in the PhD program (certain previously completed requirements count automatically, such as breadth requirement courses taken here at Columbia).
Then, once formally enrolled for the PhD later on, the student is expected to spend a minimum of two full academic years full-time on-campus, beyond the MS or CSE degree. In very rare cases, students may conduct their research off-campus in an industry or government laboratory, or at another academic institution, with the permission of the faculty advisor and the concurrence of the PhD Chair.
It is not unusual, albeit not recommended, for PhD students who have completed all of their requirements except the dissertation defense and deposit, known as "ABD" for "all but dissertation", to accept full-time positions elsewhere while writing the dissertation, normally after most if not all of the research has been completed.
As of Fall 2013, it is possible to enroll in the DES (but not PhD) program through the Columbia Video Network, for further information see http://www.cvn.columbia.edu/doctoral_cs.php.Last updated on July 9, 2014.