.bmp (Bitmap Image File) The .bmp format, also known as bitmap, is a raster graphics image file format used to store digital images. This format was developed by Microsoft for use on Windows, and it is widely supported on both Windows and macOS systems. BMP files are typically large because they contain a detailed, uncompressed representation of the image data. This format is suitable for storing high-quality digital photos, though it's not as commonly used for web or email due to its large file size compared to formats like JPEG or PNG.

PGM file format was developed alongside the open-source Netpbm package of graphics program. Developed by Jef Poskanzer in 1988, PGM was a format for storing grayscale images and supporting bitmap. The PGM file format is forward compatible with recent graphics editing software like Corel PaintShop Pro X4, ACDSee Photo Manager 14, and ACD Systems Canvas 15. Being a plain text format, PGM can be edited using any available text editor, and thus survives the quintessential changes that image files undergo when transmitted via email. PGM files come in two types, only differentiated by magic numbers – P2 and P5, which helps graphics editor software identify the data encryption standard.