The Style property identifies the size of the icon and must be 'Large' or 'Small'. The former specifies a 32x32 icon and is the default; the latter specifies a 16x16 icon. The size of the icon is not embedded within the icon data, so it is essential to specify Style correctly. Note that a single file may contain both sizes of an icon. Style is only relevant when loading an Icon from file.

If the value of the File property is set by ⎕WS, no immediate action is taken, but the corresponding file may subsequently be read or written using the FileRead or FileWrite methods.

16-bit icons contain fewer than 256 colours and each pixel is either transparent or opaque. The images in such Icons are represented by the Bits, Mask and CMap properties.

32-bit icons are 24-bit images with an 8-bit alpha channel which specifies the degree of transparency of each pixel. The pixels in these Icons are represented by the CBits property.

CBits is a rank-2 numeric array whose dimensions represent the rows and columns of pixels in the Icon. The values in CBits represent the colour and of each pixel and also its transparency.

Bits is an integer matrix whose elements define the colours of each pixel in the icon in terms of their (0-origin) indices into CMap. When the icon is displayed on the screen, the way in which these colours combine with those currently displayed on the screen (the background) is specified by Mask. This is a Boolean matrix of the same size as Bits. The following table shows how the colour of each resulting pixel is determined.

Bits	Colour	0	Colour
Mask	0	1	1
Pixel	Colour	Background	New Colour

If an element of Mask is 0, the corresponding element of Bits defines the colour of the resulting pixel that is displayed on the screen. If an element of Mask is 1, the resulting pixel that is displayed on the screen is either the current background colour or is a new colour chosen by MS-Windows to be visible against the background. A non rectangular icon is obtained by setting those elements of Bits and Mask that you want to exclude from the shape to be 0 and 1 respectively.

The size of Bits is restricted by the capabilities of the current display driver. Mask must have the same shape as Bits.

An Icon is used by setting the IconObj property or Picture property of another object to its name or ref.