Formatted and Binary Modes

ENDF tapes received from a distribution point, be they ENDF/B, JEF, JENDL, CENDL, or BROND, come in a formatted ASCII mode that can be easily read or printed. However, this is not the most efficient form to use for communicating between different processing modules in NJOY. Binary files are much more efficient because it is not necessary to repeatedly convert the data between the binary forms used in memory and the ASCII forms.

Although the ENDF format specifies a standard binary mode, NJOY uses a special blocked-binary mode that divides each ENDF "record" into one or more blocks of data of bounded size. The NJOY subroutines that read and write ENDF records know how to handle the binary mode and how to convert back and forth between binary and ASCII. NJOY normally uses a page size of 326 words for these binary blocks, which is small enough to use conveniently and large enough to reduce the total number of I/O operations to a reasonable value.

NJOY contains a special module called MODER for converting back and forth between the ASCII and binary forms. It uses negative unit numbers to indicate binary files. Therefore, the previous example of NJOY data flow would like like this when using binary mode:

       [copy an ENDF file onto "tape20"]

       20 -21
       -21 -22
         ...specific input for RECONR...
       -21 -22 -23
         ...specific input for BROADR...
       -21 -23 0 -24
         ...specific input for GROUPR...
       -24 25 -23 26
         ...specific input for DTFR...

       [copy tape25 to the DTF library]

MODER also has other capabilities. See the MODER Input Instructions.


23 January 2013 T-2 Nuclear Information Service