In ISO/IEC 646 (commonly known as ASCII) and related standards including ISO 8859 and Unicode, a graphic character is any character intended to be written, printed, or otherwise displayed in a form that can be read by humans. In other words, it is any encoded character that is associated with one or more glyphs.
In ISO 646, graphic characters are contained in rows 2 through 7 of the code table. However, two of the characters in these rows, namely the space character SP at row 2 column 0 and the delete character DEL (also called the rubout character) at row 7 column 15, require special mention.
The space is considered to be both a graphic character and a control character in ISO 646; this is probably due to it having a visible form on computer terminals but a control function (of moving the print head) on teletypes.
The delete character is strictly a control character, not a graphic character. This is true not only in ISO 646, but also in all related standards including Unicode. However, many modern character sets deviate from ISO 646, and as a result a graphic character might occupy the position originally reserved for the delete character.
In Unicode, Graphic characters are those with General Category Letter, Mark, Number, Punctuation, Symbol or Zs=space. Other code points (General categories Control, Zl=line separator, Zp=paragraph separator) are Format, Control, Private Use, Surrogate, Noncharacter or Reserved (unassigned).[1]