LD

These initials stays for Ladder Diagram

PLC

These initials stays for Programmable Logic Controller

bold

Bold text denotes menus, menu items, or dialog box buttons or options. In addition bold text denotes LD input and output parameters.        

Italic

Italic text denotes emphasis, a cross reference, or an introduction to a key concept.

Bold italic

Bold italic text denotes a note, caution or warning.

Courier

Courier font denotes text or characters that you enter using keyboard. Selections of code, programming examples, syntax examples, and messages and responses that the computer automatically prints to the screen also appear in this font.

Courier Bold

Courier Bold denotes file names

This symbol leads you through nested menu items and dialog box options to a final action. The sequence  OptionsColors directs you to pull down the Options menu and select the Color option entering the appropriate dialog box.