the ascii character set is barely large enough for us english use and lacks many glyphs common in typesetting, and far too small for universal use. many more letters and symbols are desirable, useful, or required to directly represent letters of alphabets other than english, more kinds of punctuation and spacing, more mathematical operators and symbols (× ÷ ⋅ ≠ ≥ ≈ π etc.), some unique symbols used by some programming languages, ideograms, logograms, box-drawing characters, etc. for years, applications were designed around the 64-character set and/or the 95-character set, so several characters acquired new uses. for example, ascii lacks "÷", so most programming languages use "/" to indicate division.