File Juicer
File Juicer for macOS
Overview of Formats

Search & Extract

Images

jpg jpeg 2000 gif png pdf wmf emf tiff eps pict bmp

Video

mov mpeg avi wmv

Sound

mp3 wav System 7 au aiff

Text

ascii rtf html

From:

avi cab cache chm dmg doc emlx exe ithmb m4p mht mp3 pdf pps ppt raw swf wps xls zip and other formats

.app - Mac Applications

Mac applications does not show the file extension ".app". To see this you select it in Finder and use "Get Info" from the File Menu.

To see what is inside an application you can open it with Finder. Select it with a single click with the mouse and choose "Show Package Contents" from the "Gear" (menu)button. Now you can browse the folders inside tha applications to see what's inside.

An application is a special kind of "Bundle". See API for using a Bundle

If you want to make an application, a simple way is to use Swift