The original post explains why... http://www.lysator.liu.se/c/duffs-device.html http://www.lysator.liu.se/c/duffs-device.html The VAX C compiler compiles the

The original post explains why... http://www.lysator.liu.se/c/duffs-device.html http://www.lysator.liu.se/c/duffs-device.html The VAX C compiler compiles the loop into 2 instructions (a movw and a sobleq, I think.) As it turns out, this loop was the bottleneck in a real-time animation playback program which ran too slowly by about 50%.