BMP is a standard image file format which was historically used by computers running the Windows operating system. The format is more commonly know as Bitmap files. The term bitmap was originally coined in computer programming to refer to a map of bits. Historically when you saved an image on your home PC you might have saved it as a .bhp file, this is becoming less common with .jpeg the preferred image file format with the advent of digital cameras.
Bitmap files are housed in a device-independent bitmap (DIB) format. The term device independent means that the bitmap specifies pixel color in a form independent of the method used by a display to represent color. This enables Windows to show the bitmap on any type of display device - such as your monitor.
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The .ico file extension is a file format that is used by Microsoft Windows to display an image to represent computer icons, such as programs, shortcuts, Start Menu items or directories. To associate an image with a file in Microsoft Windows a .ico file must be used. An example of an icon is the small computer image associated with 'My Computer' or the Notepad icon that is associated with the Notepad.exe application within Microsoft Windows.
The .ico file type was introduced by the first edition of Windows and has slowly evolved in terms of maximum pixel size and the level of colour support. Windows 7 currently supports icon sizes up to 256 x 256 pixels at 32 bit (comprising 24 bit colour, and 8 bit transparency). However to ensure backwards compatibility with previous versions of Windows 8 bit versions are recommended.
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