Effectiveness of G-code

One block in the G-code contains all the executable G and M-commands that are in a combined line. A line break signifies the end of a block.

A characteristic of most G-commands is that their instruction remains for the next blocks. They "take effect modally". For certain control commands, there are G-commands with an opposite instruction with which the original instruction can be reversed. For instance, there is a modal command for activating path control operation (switch on blending) and another modal command to deactivate path control operation (switch off blending).

However, a characteristic of some G-commands is that their instruction becomes effective only for the current block. For the following blocks, the modal setting automatically takes effect again. They are "effective in blocks".