A BMP is a kind of computer file that holds a picture. The letters come from bitmap: a picture built from many tiny dots, each one a little bit of colour. Windows computers have used this type of file for a long time. BMP files are often large, because they tend to keep every dot instead of squeezing the picture to save space. You still meet them on older computers and in some drawing programs, but phones and websites more often use JPEG or PNG. You usually see .bmp at the end of the file name. People say the three letters, B-M-P.

BMP 檔；點陣圖檔。台灣說「點陣圖」，中國大陸較常說「位圖」。