Simulation Program allows any sample developed for PV machines in Series 2 and 3 to be checked through very quickly and efficiently. This operation is carried out on a PC and therefore does not tie up the knitting machine in slow and expensive trials. Is is capable of revealing all the errors that may have been made in programming and which would set off one of the machine's alarms, (such as the needle detection stopmotion). It displays the program row by row, using a very straightforward system of graphics representation, showing the movement of all the needles an all the yarn feeders on the machine, thus allowing any knitting problems to be identified very quickly. It can also establish the production time for the piece with a high degree of accuracy and can help the operator to calculate the production time for the whole batch.