Jerome Fine replies: I looked at the arguments for SPLIT and you are correct, but unfortunately, the octal arithmetic: 47311 = 104270 - 34757 seems to be the problem, aside from the fact that an octal value can not include the digits 8 or 9. When you posed this question on alt.sys.pdp11, I noticed that you also received the error message: ?Split-E-Input error This would probably be due to a bad block somewhere in the last portion of the "JUL28.DSK" file. Finding that block will not be impossible, but when you do so, there are methods to copy the bad block it can be recovered by repeated attempts to read it ONE block at a time. That attempt can sometimes be accomplished by: MOUNT LD0: JUL28.DSK/NOWRITE COPY/DEVICE/IGNORE LD0: DU1: Finding the actual block that is bad is not trivial, but BINCOM can help if you then do a binary search when comparing the portions of LD0: which can be read. If you don't understand, please ask! I presume that you have more than ONE RT-11 partition to work with although your sample syntax does not demonstrate that possibility. I presume that since every RT-11 partition has a MAXIMUM of 65536 blocks and placing all 3 portions of a 35000 block file on the same RT-11 partition would require 70000 blocks - which exceeds that capacity of the RT-11 partition. Thus, even if you had not encountered a bad block in the "JUL28.DSK" file, there would have been insufficient space to output the last portion. If you have any other RT-11 questions or require more help, please ask. Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.