名词文件扩展名
1. 文件后缀名：file-by-file compression 文件压缩 | filename extension 文件后缀名 | fill pattern 填充模式
noun
1. a string of characters beginning with a period and followed by one or more letters
the optional second part of a PC computer filename
e.g. most applications provide extensions for the files they create
most BASIC files use the filename extension .BAS
Synonym: extension file name extension