M0 is the _______ command.

M0 is known as a command used in CNC programming that signifies a program stop. When this command is encountered in a program, it instructs the CNC machine to halt its operation until the operator manually resumes the process. This command is particularly useful in situations where an operator needs to inspect the workpiece, perform maintenance, or make adjustments.

Using M0 does not affect any program variables or positions; it simply pauses the execution. This contrasts with other types of commands that may initiate, resume, or repeat sequences in a program. M0 serves as a safety and control feature, providing flexibility during machining operations while ensuring the operator can verify the machining process without risking errors or accidents.