1. Pause instruction: G04X(U)_/P_ refers to the pause time of the tool (the feed stops, the spindle does not stop), and the value after the address P or X is the pause time. The value after X should have a decimal point, otherwise it will be calculated in one thousandth of this value, in seconds (s). The value after P cannot have a decimal point (that is, expressed as an integer), and is in milliseconds (ms). However, in some hole machining commands (such as G82, G88 and G89), in order to ensure the roughness of the hole bottom of the CNC machining center, when the tool is processed to the bottom of the hole, a pause time is required. At this time, only the address P can be used. Indicates that if it is represented by address X, the control system of the CNC machining center regards X as representing the coordinate value of the X axis for execution. 2. The difference and connection between M00, M01, M02, M03: 1) M00: This is an unconditional pause command for the program. When the program is executed, the feed stops and the spindle stops. To restart the program, you must first return to the JOG state, press CW (spindle forward rotation) to start the spindle, and then return to the AUTO state, press the START key to start the program. 2) M01: Program selective pause command. Before the program is executed, the OPSTOP key on the control panel must be turned on to execute it. The effect after execution is the same as M00, and the program must be restarted as above. 3) M02 is the main program end instruction. When this instruction is executed, the feed will stop, the spindle will stop, and the coolant will be shut off. But the program cursor of the CNC machining center stops at the end of the program. 4) M30 is the end command of the main program. The function is the same as M02, but the difference is that the cursor returns to the program head position, regardless of whether there are other blocks after M30. M00 and M01 are often used: When the CNC machining center processes the workpiece to the middle, it will inspect the size of the workpiece or remove chips.