Areas allow input and output of complete lists of based variables as one unit, to and from RECORD files. On output, the area extent, together with the 16 bytes of control information, is transmitted, except when the area is in a structure or union and is not the last item in it--then, the declared size is transmitted. Thus the unused part of an area does not take up space on the data set.
Because the extents of areas can vary, varying length records should be used. The maximum record length required is governed by the area length (area size + 16).