# Subject numbering

Starting with fall 2022, EECS will be using new numbers for almost all of its subjects. This page explains the new system and the reasons for the change, and answers some common questions.

To go straight to the renumbering, use this link:

Reason for the change. The old Course 6 numbering scheme had become overgrown, crowded, and arbitrary, and didn’t reflect the new structure of the EECS department (which now has three parts: EE, CS, and AI+D) or recent changes to curricula (6-2, 6-3, and the new 6-4). The new numbering defragments the space and brings related areas together in a consistent scheme that hopefully makes more sense to everybody. There are more details about the reasons and process for renumbering in a slide presentation.

All 3-digit numbers (6.xxx) have become 4-digit numbers (6.yyyy). If you see a number with 3 digits after the decimal point, then it is probably an old number. If you see a number with 4 decimal places, then it is probably a new number. The only 4-digit exceptions in the old system were 6.0001, 6.0002, 6.1151, 6.1311, and 6.9021/A/B. There are no 3-digit numbers in the new system.

Lettered subjects (6.UAR, 6.UAT, 6.THM, 6.Axx, 6.Sxxx, 6.Cxx, etc.) are unchanged. Only subjects that have a digit after the decimal point were renumbered.

Where possible, the old number is still shown in a subscript, like 6.new[6.old]. EECS websites (including EECSIS and Who’s Teaching What) will use this notation to show both new and old numbers during the transition period. MIT-wide websites (including Websis, Canvas, and the final exam schedule) will use only the new numbers.

Most new numbers end with 0. Most new numbers have the form 6.xxx0. When you are talking about the subject out loud, you can usually ignore the trailing zero and just read the first three digits as significant. For example, 6.2500[6.012] might be read as “six-two-fifty,” and 6.1210[6.006] as “six-one-two-one.” The trailing 0 is important to distinguish between new numbers and old numbers, and MIT’s systems will expect the full 4-digit number.

Numbers ending 6.xxx1 or 6.xxx2 are variants of a base subject 6.xxx0. For example, 6.5830/6.5831[6.830/6.814] are the graduate and undergraduate versions of Database Systems, taught together, and the combination might be read simply as “six-five-eight-three.” The last digit indicates the level: 6.xxx1 is an undergraduate variant of a typically graduate-level base subject, while 6.xxx2 is a graduate variant of an undergraduate base subject.

Numbers ending 6.xxxA/B/L are submodules. For example, 6.100A[6.0001] and 6.100B[6.0002] are the first and second half-semester parts of Introduction to Computer Science and Programming.

Subjects are organized by level and subarea. 6.1xxx-6.4xxx are introductory and undergraduate subjects. 6.5xxx-6.8xxx are graduate or advanced undergraduate. Each of these ranges is divided into corresponding subareas as shown below.

Introductory subjects are found at the start of a subarea. Here are the new numbers for the most common entry points into Course 6:

Degree requirements can be satisfied by both old and new numbers. If you took a subject under an old number, it can be used to satisfy degree requirements that show the new number, and vice versa. This is just a renaming.

Your transcript will show the number in effect when you took the subject. For 6.new[6.old], if you took the subject prior to fall 2022, then your transcript will show its number as “6.old.” If you take the subject in fall 2022 or later, your transcript will show “6.new.”