[U]

[..]
  1. UCHAR_MAX
  2. UESP
  3. UINT_MAX
  4. ULONG_MAX
  5. UNBLK_FIRST
  6. UNBLK_SECOND
  7. USED
  8. USHRT_MAX
  9. UTS_MACHINE
  10. UTS_NODENAME
  11. UTS_RELEASE
  12. UTS_SYSNAME
  13. UTS_VERSION
[..]