MS Paint

Paint (formerly Paintbrush for Windows) is a simple graphics painting program that has been included with all versions of Microsoft Windows. It is often referred to as MS Paint or Microsoft Paint. The program opens and saves files as Windows bitmap (24-bit, 256 color, 16 color, and monochrome, all with the .bmpextension), JPEG, GIF (without animation or transparency, although the Windows 98 version, a Windows 95 upgrade, and the Windows NT4 version did support the latter), PNG (without alpha channel), and TIFF(without multiple page support). The program can be in color mode or two-color black-and-white, but there is no grayscale mode. For its simplicity, it rapidly became one of the most used applications in the early versions of Windows—introducing many to painting on a computer for the first time—and still has strong associations with the immediate usability of the old Windows workspace.

Source: Wikipedia