What does HackerNews think of minifb?
MiniFB is a small cross platform library to create a frame buffer that you can draw pixels in
Language:
C
MiniFB is also nice for this purpose: https://github.com/emoon/minifb
GLFW+GL provides a portable way to do this though. Otherwise you'd need to mess with platform-specific window systems.
(something like minifb would be a more minimal option though: https://github.com/emoon/minifb)