1. meaning of letters in NC program
O: Program number
N: Program segment number, set program sequence number
G: Preparation function
X/y/z: dimension character, axis movement command
A/b/c/u/v/w: additional axis movement command
R: Arc radius
I/j/k: arc center coordinate (vector)
F: Feed, set feed rate
S: Spindle speed, set spindle speed
T: Tool function, set tool number
M: Auxiliary function, on / off control function
H/d: tool offset number, set tool offset number
P/x: delay, set delay time
P: Program number instruction, set subprogram sequence number (e.g. subprogram call: m98p1000)
50: Repeat, set subroutine or fixed cycle repetition times (e.g.: M98 P1000 L2, omitting l stands for L1)
P/w/r/q: parameters, parameters for fixed recycling (such as tapping g98/ (G99) g84 x_ Y_ R_ Z_ P_ F_)
