Basic Programming Terms – CNC Structure in 4 Steps

1. Character

A character is the smallest unit in CNC programming. It may be a letter, digit, or symbol. Characters combine to form words in the CNC language.

CNC programs use letters from the alphabet and digits from 0 through 9. Numbers may be written with or without decimal points, depending on the programming mode and machine control.

Common symbols include the decimal point, parentheses, minus sign, and percent sign. The available symbols depend on the control.

2. Word

A word is a combination of characters. It typically consists of a capital letter followed by a number and, when required, a symbol. Words specify information such as spindle speed, feed rate, position, commands, and other machine functions.

3. Block

A block, also called a sequence block, contains one or more words. While an individual word supplies one piece of information, a block combines instructions into a complete command or cycle.

Blocks are written on separate lines and terminated by an end-of-block code.

4. Program

A CNC program is an ordered collection of blocks that directs the machine through the operations required to produce a part. Every block must contain the correct characters and words for its command to work properly.

A program generally begins with a program number, arranges its blocks in machining order, and finishes with a program-stop or cancellation code.

CNC Program Structure

Character → Word → Block → Program