In computer graphics, the X Window System uses XBM (X BitMap), an ASCII monochrome , for storing cursor and icon bitmaps used in the X GUI. XBM files differ markedly from most image files in that they take the form of C language source files. This means that they can be compiled directly into an application without any preprocessing steps, but it also makes them far larger than their raw pixel data would be (each byte of image data takes 6 bytes in a XBM file).