The used coordinate system is based on the classical model having its coordinate origin at the lower left. The zero of the horizontal X coordinate is situated on the left edge of the sheet. Its value increases in the right direction. The zero of the vertical Y coordinate is situated on the lower edge of the sheet. Its value increases in the up direction. The unit distance corresponds to the width of the item (icon), i.e. 32 graphic pixels. This makes it possible to use the coordinates easily (The indexing of the squares 0, 1, 2 ... corresponds to their coordinates) maintaining the possibility of working with fine graphics (using decimal numbers). This coordinate system is used by all functions of the Peter system.