1 2 3The source listing is preceded by a cross-reference that lists every defined 4constant, struct, global variable, and function in xv6. Each entry gives, 5on the same line as the name, the line number (or, in a few cases, numbers) 6where the name is defined. Successive lines in an entry list the line 7numbers where the name is used. For example, this entry: 8 9 swtch 2658 10 0374 2428 2466 2657 2658 11 12indicates that swtch is defined on line 2658 and is mentioned on five lines 13on sheets 03, 24, and 26. 14