Display device, and display method

A display device comprising a processor, the processor being configured to:

• acquire tool position data;
• acquire a machining program;
• save the acquired tool position data and an index of the machining program in association with each other;
• calculate a tool machining trajectory from the acquired tool position data and displays the tool machining trajectory;
• select a portion on the machining trajectory from the displayed tool machining trajectory
• select a program block of the machining program corresponding to the index of the machining program saved in association with the portion, which has been selected, on the machining trajectory;
• and
• display, on the displayed machining program, the selected program block differently from other character strings,
• wherein the processor acquires an index of the machining program every time the processor acquires the tool position data, and separately acquires the machining program independently of acquisition of the tool position data, and
• the processor saves, at each point of time of acquisition, the acquired position data and the acquired machining program index in association with each other.