In Harry Potter do people choose their dorm mates?

Answer 1

Oxford University does not have "dorms" in the American sense: students belong to "colleges" - self-governing institutions of the University which vary considerably in size (although never more than a few hundred undegraduate students) & character. Students almost always have individual rooms in their colleges, although some may share "outside" accommodation (eg rented houses) for their final undergrad year.

Typically, Oxford colleges consist of a cluster of buildings centred around a quadrangle (sometimes 2 or more linked "quads"- St John's has 7!), including lecture/ teaching rooms, a college library (distinct from University Libraries), a Hall (usually also the dining area) & kitchens, plus admin & accommodation buildings, common rooms (for junior - ie undergrad - & senior college members), & usually a chapel.

The main entrances to colleges are typically pretty imposing: often arched gateways; usually "guarded" by senior college staff ("servants" in the older more traditional colleges, who often wear formal attire & black bowler hats. There are also University "Proctors"- a small private police force - who are informally called "Bulldogs"!) who control access. The quadrangles (typically beautifully maintained; "historic"; calm & dignified) are so attractive that most students love living "in college", & value highly the other exclusive facilities available to them therein: all part of the "Oxford Experience"!

Some colleges are very traditional, & have formal dining halls where students wear gowns at meals, & are waited on by college servants; Latin graces are said, & all sorts of Medieval customs observed. Most these days are, however, less "stuffy": formal dinners only occur once a month or so, & on a day to day basis meals in hall are cafeteria/ self-service style, usually paid for with "swipe" cards etc..

Oxford University undergraduate students usually live in their colleges throughout their degree courses. They do not share rooms: typically a student has a room on a "staircase" leading up from doorways facing out on the central quad. There are variations on this (eg at Keble students live in rooms off "landings" not "staircases"), especially in the newer/ more modern colleges, but students nearly always have individual rooms.

Room sizes vary: in some of the older, wealthier, grander colleges (eg Christ Church) students may have "sets" of 2-3 rooms. That stated, many rooms in the older colleges tend, by modern standards, to be quite small - eg 10 x 10 feet. Generally, bathroom & other facilities (eg small kitchens) are shared by students living on the same "staircase", but the more modern college rooms (usually larger than Medieval "cells") often have such facilities "en suite". NB Irrespective of how "Medieval" they may be, all Oxford student rooms are these days wired for internet access.

Most Oxford colleges also own substantial properties in adjacent streets. Often these are rented to their students: typically graduate students or married students with families. Sometimes, however, senior undergraduates may also live in such houses - usually groups of friends who've opted to share in preference to spending their final year in a traditional room on a staircase in college.

Answer 2

No. The Sorting Hat divides up the 1st years into their houses. Each of the years is put into their own dorm room with their house mates.