Users create this software themselves and often overlook how important it is. In some types of embedded systems, the application software and the operating system software may be indistinguishable to the user, as in the case of software used to control a VCR, DVD player or Microwave Oven.
You can jam milk through pretty small holes with force like that. Before homogenization, fat globules range in size from 1-10 microns (a micron = ~0.00004 inch). After, the size range is reduced to 0.2-2 microns.
It is entirely possible to have milk that has been homogenized but not pasteurized, or pasteurized but not homogenized. If both processes are to be performed, however, homogenization typically comes last, since the heat of the pasteurization tends to make the fat breakdown easier.