True Type 同 Open Type有分別嗎?

當然有, 參考以下文章,
基本上 OpenType 是源自於 MS 的 TrueType Open 字型，而 TrueType Open 字型是源自於 TrueType 字型，所以這些字型可以說是系出同門，基本的 container 格式是相同的。

TrueType Open font 和 TrueType font 最大的不同是：
增加了 GSUB(Glyph Substition), GPOS(Glyph Position), BASE(baseline), JSFF(Justification), GDEF(Glyph Definition) 等五個 table 來控制字的置放、取用機制。

OpenType font 和 TrueType Open font 最大的不同是：
引進 CFF table 來存放 ps outline 資料，這相當於 TTF 的 glyf table，這些都是主要的字型實體資料。
所以，在 OpenType font 會有兩種不同字型實體資料的字型出現：

TrueType format with TrueType outline(*.ttf, *.ttc)
TrueType format with PS outline(CFF)(*.otf) 或稱為 CFF OpenType font。
因此，並不是說 *.ttf 就不是 OpenType font。主要還是要看裡頭的 table。會以 *.otf 做延伸檔名的，通常就是 CFF OpenType，不同的地方是字型實體資料是 CFF(Compact Font Format) table，而不是原來 TTF 的 glyf table。
其他補充：

OpenType font 包括了 Adobe CID-Keyed font 的技術，像目前 AR6/7 所附上的 OpenType font，其實是 CID-Keyed font 但穿上了 TrueType 的衣服（因為 CFF 本來就可以含 CID-Keyed font）。
只要判斷出字型含有 DSIG(Digital Signature) table，大致上就可以判定他是 OpenType font。然後再來判斷是含有 CFF table 或是 glyf table 就可以判斷是 CFF outlines 或是 TrueType outlines。

http://en.wikipedia.org/wiki/TrueType
TrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript. The primary strength of TrueType was originally that it offered font developers a high degree of control over precisely how their fonts are displayed, right down to particular pixels, at various font heights. (With widely varying rendering technologies in use today, pixel-level control is no longer certain.)

http://en.wikipedia.org/wiki/OpenType

OpenType is a scalable computer font format initially developed by Microsoft, later joined by Adobe Systems. OpenType was first announced in 1996, with a significant number of OpenType fonts starting to ship in 2000–2001. Adobe completed conversion of its entire font library to OpenType around the end of 2002. As of early 2005, there were around 10,000 fonts available in OpenType format, with Adobe's library making up under a third of the total. As of 2006, every major font foundry and many minor ones were developing fonts in OpenType format.

2007-05-07 15:36:48 補充：
TrueType- AppleOpenType- Microsoft