PLT (plotter) and CNC (computer numerical control) programming are both used to control machines that cut or shape materials, but they are used for different types of machines and serve different purposes.

PLT programming is used to control plotters, which are machines that use a pen or marker to draw or write on a surface. These machines are typically used for cutting or drawing large format graphics, such as signs or posters. The programming language used is HPGL (Hewlett-Packard Graphics Language) and the program is typically created using a CAD software.

CNC programming, on the other hand, is used to control CNC machines, which are machines that use cutting tools to shape or cut materials. These machines are typically used for manufacturing or prototyping parts, and can include lathes, mills, routers, and other types of machines. The programming languages used for CNC machines are typically G-code or M-code, and the program is typically created using a CAD and CAM software.

In summary, CNC programming is used to control machines that shape or cut materials, while PLT programming is used to control machines that draw or write on a surface.