BSEGY and SU (before XDR) share many headers. However, if SU is compiled with XDR, the data and headers become byte swapped. SU with XDR is referred as SUXDR.
bswp infile idfc npts
infile = input file name (4char minimum)
Data format
idfc 1=4 byte floating point
2=4 byte integer
3=2 byte integer
npts =number of samples per trace