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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:
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