HEIDENHAIN SW 54843x-03 DIN Programming - Manual (Page 37)

HEIDENHAIN MANUALplus 620, CNC PILOT 640 37
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Elements of an NC program
An NC program consists of the following elements:
 Program name
 Program section codes
 Units
 NC blocks
 Commands for program structuring
 Comment blocks
The program name begins with "%" followed by up to 40 characters
(numbers, uppercase letters or underscore; no diacritical marks) and
the extension "nc" for main programs or "ncs" for subprograms. The
first character must be a number or a letter.
Program section codes: When you create a new NC program, certain
program section codes are already entered. You can add new codes
or delete existing ones, depending on your program requirements. An
NC program must contain at least the MACHINING and END section
codes.
The unit begins with this keyword followed by the identification of
the unit (ID"G..."). The following lines contain the G, M and T
functions of this machining block. The unit ends with
END_OF_UNIT followed by a check digit.
NC blocks begin with an N followed by a block number (with up to five
digits). The block numbers do not affect the sequence in which the
program blocks are executed. They are only intended for identifying
the individual NC blocks.
The NC blocks of the HEADER and TURRET sections are not included
in the block number organization of the editor.
You can use program jumps, repeats and subprograms to structure
a program (example: machining the beginning/end of a bar, etc.).
Input and output: With "input" you can influence the flow of the NC
program. Using "output," you can communicate with the machinist.
Example: The machinist is required to check measuring points and
update compensation values.
Comments are enclosed in brackets "[...]." They are located at the end
of an NC block or in a separate NC block. Press the key combination
CTRL+K to convert an existing block into a comment (and vice versa).
You can also enclose more than one program line in square brackets
to mark them as a comment. To do this, enter a comment containing
the character "[" and conclude the section by entering another
comment containing the character "]".