Graphics and Interaction
A 2-bit colour bitmap which is used to store the shape of another bitmap. Masks are the same size as their related bitmap. A zero bit in a mask means that the related bitmap is transparent there, a one means that the other bitmap is not transparent in that pixel.
Read This First
Multipurpose Internet Mail Extensions. A way of associating foreign (non-EPOC) files to their correct type and application.
Files which are foreign to EPOC are recognised by MIME recognisers located in System\Recogs\ under ER5. OPL applications can register themselves as being able to handle a given kind of MIME-recognised file using the ER5 OPL MIME keyword.
This is in addition to the standard UID-based recognition of files provided by EPOC.
See also OPL and MIME 
and OPL applications.
Introducing OPL
One or more procedures for OPL to follow. Each OPL module is stored in a single program file.
Advanced Topics
An EPOC picture file or MBM. MBMs can contain one or more bitmaps and their masks.