4 9 ▁commands , ▁but ▁follow ▁neither ▁the ▁Ex cell on ▁nor ▁the ▁IP C - NC - 3 4 9 ▁specification . ▁Comm ands ▁are ▁not ▁used ▁properly , ▁or ▁are ▁used ▁in ▁a ▁s ynt act ically ▁incorrect ▁way , ▁and ▁binary ▁data ▁objects ▁may ▁be ▁included . ▁Sometimes ▁the ▁historic ▁E IA ▁or ▁E BC D IC ▁character ▁encoding ▁is ▁used . ▁Usually ▁the ▁header ▁is ▁incomplete : ▁the ▁scale ▁or ▁the ▁tool ▁diam eters ▁is ▁missing . ▁Sometimes ▁there ▁is ▁no ▁header ▁at ▁all , ▁and ▁the ▁file ▁only ▁contains ▁tool ▁numbers , ▁with ▁an ▁un spec ified ▁diameter , ▁and ▁X , Y ▁coordinates , ▁in ▁an ▁un spec ified ▁unit . ▁They ▁are ▁often ▁called ▁Ex cell on ▁files ▁although ▁they ▁are ▁und ef in ite ▁NC ▁files . ▁▁ ▁No ▁specification ▁exists . ▁It ▁is ▁not ▁always ▁clear ▁what ▁the ▁purpose ▁of ▁these ▁st unted ▁files ▁is . ▁ ▁An ▁example : ▁▁▁ ▁% ▁▁ ▁T 0 1 ▁▁ ▁X 0 0 6 2 7 2 Y 0 0 1 0 9 2 ▁▁ ▁X 0 0 6 3 5 4 Y 0 0 1 0 9 3 ▁▁ ▁X 0 0 6 6 5 3 Y 0 0 1 0 9 2 ▁▁ ▁... ▁▁ ▁T 0 2 ▁▁ ▁X 0 0 8 0 9 1 Y 0 0 1 7 5 4 ▁▁ ▁X - 0 0 2 0 2 8 ▁▁ ▁M 3 0 ▁ ▁The ▁tool ▁diam eters ▁and ▁how ▁to ▁interpret