Section classification is accomplished by means of a system of segment-numbers. The segment-number is included in the section header.
The segment-number must be an integer ranging in value from 0 through 99.
If the segment-number is omitted from the section header, the segment-number is assumed to be 0.
Sections in the declaratives must contain segment-numbers less than 50.
The segment-number must be a signed integer, but must not be a floating-point literal.
All sections which have the same segment-number constitute a program segment. All sections which have the same segment-number need not be physically contiguous in the source program.
Segments with segment-number 0 through 49 belong to the fixed portion of the object program.
Segments with segment-number 50 through 99 are independent segments.
Structure of Program Segments