File extension

File extension
Used to recognize file type.
.mp3 - audio file
.Mp4 - video file
.text - text file
.exe - executable file
.gif - graphical interchange format
.jpeg - joint photographic expert group
.doc - document file of ms word
.xls - excel file
.ppt - presentation file
.html - html file
.mdb - access file
.zip - compressed file