I suggest you DON"t try to read NC.ARC files. --these file designed for archive --back up only. 

this also Siemens suggestion. something like you can use Win Word, why you need to know the source code of it.

other member already answer you  the contents of NC.arc--I make it simple --NC.arc is contents all parameters which stored in NC memory, which will be lost when battery is low.  

AutoGen_497010

Hello Experts, 

We do have Siemens 840 D PL NC ARC files.  I would like to know how to read these files specially understand instructions written in these files.  

Any help or manual suggestion is highly requested. 

Thanks in advance 

 all you mentioned are NC Programming instructions inside Program, like other NC program CODE--G01 F500 X-12... and so on, . when making NC archive. all NC Program loaded in the NC memory will be all archived --you no need to worry about them. again NC.arc is only for back up.

Tips: if you want to know how to back up NC Program, which  can be back UP AND READIBLE 

You need to know the NC Program location--example using "NC_Program.MPF" when 1st generated, it will be in the HDD (IF Your machine has PCU50) . when you load it to run , it will be transfer to NC memory (no longer in HDD) --so there are 2 ways to save/back up NC program:

#1--unload  from NC memory, they will be back to HDD

#2--in Service area, back up (not Archive ) NC Program only in Tape format, from NC memory to HDD (possible further transfer out to external devices, such as USB storage or using RS232 interface) 

AutoGen_497010

Hello, 

Thank you very much for your reply. 

What I want to understand is instructions like,  SBOLF,  JUMPF,  ZSD,  C97,  ISFILE, STOPRE,  etc.  etc.  used in NC arc files. 

Hope it is clear now. 

Thanks in advance.