Important update underlined below, July 30, 2018 - Please read below if you are an undeclared junior!
Special Notice for 2018-2019. SYMSYS 1, which is usually taught in the Autumn Quarter, will be taught in the Winter in 2018-2019. This means that if you are an undergraduate who wants to declare Symbolic Systems as your major and have not yet taken SYMSYS 1, you will need to wait until after the add/drop deadline in Winter Quarter before you can declare, at which point you must be enrolled in SYMSYS 1. However, because the scheduling of SYMSYS 1 is a break from our usual pattern, we recognize that some juniors who were planning to take SYMSYS 1 in the fall and then declare may be unable to take the course in the Winter because they have already committed to going away during Winter Quarter (e.g. to an overseas campus).
If you are a junior with an enrollment hold for not declaring a major, you can declare during the Autumn Quarter and your declaration will be approved if you provide a letter of admission to another campus for Winter Quarter. This only applies to juniors under a registration hold for not yet declaring (or students declared in another major who entered Stanford in 2016 or earlier), who can establish that they will not be on campus in the Winter. Undeclared Juniors who are considering majoring in Symbolic Systems but who have not yet taken SYMSYS 1, and who are *not* going to be away for Winter Quarter, can meet with their UAR Advisor (AAD or AARC Advisor) to discuss their academic plans prior to enrollment for Winter Quarter in order to have their enrollment hold released. They may then declare and get approval for a major in Symbolic Systems after the add/drop deadline for Winter Quarter if they are enrolled in SYMSYS 1 at that point.
Our current intention is to resume teaching SYMSYS 1 in the Autumn in 2019-2020, so we are hoping the accommodation for undeclared juniors going overseas in Winter will only be necessary in 2018-2019.
For more info see General Questions, Declaring, and Academic Advising for Undergraduate Majors.