Siemens SINUMERIK 808D ADVANCED Programming And Operating Manual page 98

See the following illustration for start of the tool radius compensation with G42 as example:
The tool tip goes around the left of the workpiece when the tool runs clockwise using G41; the tool tip goes around the right
of the workpiece when the tool runs counter-clockwise using G42.
Information
As a rule, the block with G41/G42 is followed by the block with the workpiece contour. The contour description, however,
may be interrupted by 5 blocks which lie between them and do not contain any specifications for the contour path in the
plane, e.g. only an M command or infeed motions.
Programming example
N10 T1
N20 G17 D2 F300
N25 X0 Y0
N30 G1 G42 X11 Y11
N31 X20 Y20
M30
After the selection, it is also possible to execute blocks that contain infeed motions or M outputs:
N20 G1 G41 X11 Y11
N21 Z20
N22 X20 Y20
98
; Correction number 2, feed 300 mm/min
; P0 - starting point
; Selection right of contour, P1
; Starting contour, circle or straight line
; Selection to the left of the contour
; Infeed movement
; Starting contour, circle or straight line
Programming and Operating Manual (Milling)
6FC5398-4DP10-0BA1, 01/2014