To define a record sequential file with fixed-length records:
 file-control.
     select recseq
         assign to "recseq.dat"
         organization is record sequential.
...
 file section.
 fd recseq
    record contains 80 characters.
 01 recseq-fd-record   pic x(80).
You could simply use ORGANIZATION IS SEQUENTIAL, as record sequential is the default for sequential files, as long as the SEQUENTIAL Compiler directive is not set.