! # % & * + - / 8 : < = > ? @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [ \ ^ _ ` { | ~
            
- uc
    
- Character classes
    - uc
- ul
    
- Character classes
    - ul
- unanchored
    
- unanchored
- unattached
    
- global, local, constant, field
- unbuffered
    
- buffered, unbuffered
- underscore
    
- _ (string continuation)
- Unicode
    
- Character set encoding
    - Unicode (OMUNICODE)
    - unicode.block-boundaries
    - unicode.block-name
    - unicode.general-category
    - unicode.omunicode-version
- unicode.block-boundaries
    
- unicode.block-boundaries
- unicode.block-name
    
- unicode.block-name
- unicode.general-category
    
- unicode.general-category
- unicode.omunicode-version
    
- unicode.omunicode-version
- union
    
- union
- Unix
    
- Platforms
- unless
    
- do when, do unless
    - when, unless
- unlock file
    
- vfs.unlock
    - vfsUnlock
- unprefixed
    
- import, supply, prefixed by, unprefixed, use
- updating records in a table
    
- db.update
    - dbTableUpdate
- uppercase
    
- uc
    - ul
- upto
    
- Pattern matching
- up-translate
    
- Aided translation types
    - Managing coroutines
    - up-translate
- URI
    
- URI handling (OMURI)
- URI manipulation
    
- uri.canonical
    - uri.collapse
    - uri.extend
    - uri.relative
- URI validation
    
- uri.parse
- use
    
- import, supply, prefixed by, unprefixed, use
- usemap
    
- usemap
- user defined data type
    
- record, declare record
    - Records
    - Records, extended
- user input
    
- User input, receiving
- using
    
- Attribute aliases
    - using
    - using group
    - using input as
    - using nested-referents
    - using output as
    - using referents
- using attributes
    
- Attribute aliases
    - using attributes
- using group
    
- Groups
    - using group
- using input as
    
- Input
    - Input scopes
    - using input as
- using nested-referents
    
- Referents
    - using nested-referents
- using output as
    
- Output
    - Output scopes
    - output
    - using output as
- using referents
    
- using referents
- UTF-16
    
- UTF-16 (OMFFUTF16)
    - utf16.omffutf16-version
    - utf16.reader
    - utf16.writer
- utf16-input-file
    
- utf16-input-file
- utf16-output-file
    
- utf16-output-file
- UTF-32
    
- UTF-32 (OMFFUTF32)
    - utf32.omffutf32-version
    - utf32.reader
    - utf32.writer
- UTF-8
    
- Character encodings, international (OMEFIO)
    - Character set encoding
- UTF-8 encoding function library
    
- utf8.byte-order-mark
    - utf8.char
    - utf8.code-point
    - utf8.encoding
    - utf8.invalid-code-point
    - utf8.length
    - utf8.multi-byte-char
    - utf8.overlong-sequence
    - utf8.single-byte-char
- UTF-8 text processing legacy library (UTF8PAT)
    
- multi-byte-utf8-char
    - single-byte-utf8-char
    - UTF-8 text processing (UTF8PAT legacy)
    - utf8-char
    - utf8-char-number
    - utf8-encoded
- Utilities legacy library (OMUTIL)
    
- Utilities (OMUTIL legacy)
    - UTIL_Env
    - UTIL_ExpRand
    - UTIL_GetEnv
    - UTIL_GetMilliSecondTimer
    - UTIL_GetProcessId
    - UTIL_IsVersionCompatible
    - UTIL_LibraryVersion
    - UTIL_Rand
    - UTIL_Sleep
    - UTIL_SortIntegersByKey
    - UTIL_SortIntegersByValue
    - UTIL_SortStreamsByKey
    - UTIL_SortStreamsByValue
    - UTIL_SortSwitchesByKey
    - UTIL_Srand
    - UTIL_UniformRand
- Utilities library (OMUTIL)
    
- util.environment
    - util.millisecond-time
    - util.omutil-version
    - util.process-id
    - util.sleep
    - util.system-temporary-directory
    - Utilities (OMUTIL)