EDIT Character Combinations The dotted circle serves as a placeholder that can be replaced by another basic character.
In a textfile, the base-character is stored first, followed by the combining mark.
 
EDIT Font Implementation In a vector-font (e.g. TrueType) the combining characters have a width of 0, therefore the curser is on the same position regardless of if it is located before or after the character.

A good font-rendering program will adjust the size and position of the combining marks to match the base-character.
 
U+20D0U+20D1U+20D2U+20D3U+20D4U+20D5U+20D6U+20D7U+20D8U+20D9U+20DAU+20DBU+20DCU+20DDU+20DEU+20DFU+20E0U+20E1U+20E2U+20E3U+20E4U+20E5U+20E6U+20E7U+20E8U+20E9U+20EAU+20EBU+20ECU+20EDU+20EEU+20EFU+20F0 NOT ASSIGNEDU+20F1 NOT ASSIGNEDU+20F2 NOT ASSIGNEDU+20F3 NOT ASSIGNEDU+20F4 NOT ASSIGNEDU+20F5 NOT ASSIGNEDU+20F6 NOT ASSIGNEDU+20F7 NOT ASSIGNEDU+20F8 NOT ASSIGNEDU+20F9 NOT ASSIGNEDU+20FA NOT ASSIGNEDU+20FB NOT ASSIGNEDU+20FC NOT ASSIGNEDU+20FD NOT ASSIGNEDU+20FE NOT ASSIGNEDU+20FF NOT ASSIGNED
U+20D0 COMBINING LEFT HARPOON ABOVE
U+20D1 COMBINING RIGHT HARPOON ABOVE
U+20D2 COMBINING LONG VERTICAL LINE OVERLAY
U+20D3 COMBINING SHORT VERTICAL LINE OVERLAY
U+20D4 COMBINING ANTICLOCKWISE ARROW ABOVE
U+20D5 COMBINING CLOCKWISE ARROW ABOVE
U+20D6 COMBINING LEFT ARROW ABOVE
U+20D7 COMBINING RIGHT ARROW ABOVE
U+20D8 COMBINING RING OVERLAY
U+20D9 COMBINING CLOCKWISE RING OVERLAY
U+20DA COMBINING ANTICLOCKWISE RING OVERLAY
U+20DB COMBINING THREE DOTS ABOVE
U+20DC COMBINING FOUR DOTS ABOVE
U+20DD COMBINING ENCLOSING CIRCLE
U+20DE COMBINING ENCLOSING SQUARE
U+20DF COMBINING ENCLOSING DIAMOND
U+20E0 COMBINING ENCLOSING CIRCLE BACKSLASH
U+20E1 COMBINING LEFT RIGHT ARROW ABOVE
U+20E2 COMBINING ENCLOSING SCREEN
U+20E3 COMBINING ENCLOSING KEYCAP
U+20E4 COMBINING ENCLOSING UPWARD POINTING TRIANGLE
U+20E5 COMBINING REVERSE SOLIDUS OVERLAY
U+20E6 COMBINING DOUBLE VERTICAL STROKE OVERLAY
U+20E7 COMBINING ANNUITY SYMBOL
U+20E8 COMBINING TRIPLE UNDERDOT
U+20E9 COMBINING WIDE BRIDGE ABOVE
U+20EA COMBINING LEFTWARDS ARROW OVERLAY
U+20EB COMBINING LONG DOUBLE SOLIDUS OVERLAY
U+20EC COMBINING RIGHTWARDS HARPOON WITH BARB DOWNWARDS
U+20ED COMBINING LEFTWARDS HARPOON WITH BARB DOWNWARDS
U+20EE COMBINING LEFT ARROW BELOW
U+20EF COMBINING RIGHT ARROW BELOW
U+20F0 
U+20F1 
U+20F2 
U+20F3 
U+20F4 
U+20F5 
U+20F6 
U+20F7 
U+20F8 
U+20F9 
U+20FA 
U+20FB 
U+20FC 
U+20FD 
U+20FE 
U+20FF 
CHARACTER  < BLOCK > 
U+20D0 – U+20FF Combining Diacritical Marks for Symbols
DEUTSCH : ENGLISH