This format was developed by Apple for storing vector and bitmap images with metadata. It was the main format for the QuickDraw graphics software. PCT supports 32-bit and 24-bit images. At the moment, the format is obsolete and has been superseded by more functional solutions.
This format is a vector images file in the Sketch Drawing program, which serves to edit and create interface designs, applications and software shells. SK-files contain objects and layers which can be edited independently of each other.