Screen Section - COBOL

The syntactic structure of the Screen Section resembles that of the Working-Storage Section. That is, it consists of a section header followed by zero, one, or more entries, each of which consists of a required level number followed by a series of optional clauses.

The entries specify the appearance of a rectangular display area called a screen. The maximum meaningful horizontal and vertical dimensions of the screen are determined by the hardware characteristics of the terminal associated with the run unit. The common limit for the horizontal dimension is 80 character positions, and the common limit for the vertical dimension is 25 lines.

Screen entries may be used to define all or any portion of the physical screen, and the entire screen or any subregion of it may be redefined as many times as is needed by the program.

Level numbers are used in the same way as in the other sections of the Data Division. That is, level 77 entries are used to describe screen items not part of a larger structure, and not subdivided into subordinate entries. Level numbers 01 through 49 can be used to define screen entries that are organized in a hierarchical structure: level 01 is the most inclusive. Level numbers 66 and 88 may not be used in the Screen Section.

Each entry in the Screen Section may define a screen-name. The rules regarding uniqueness of screen-names are the same as the rules regarding uniqueness of data-names in the other sections of the Data Division. That is, a screen-name defined at the 01 or 77 level in the Screen Section must be unique only if there is a reference to it elsewhere in the program. Subordinate screen-names (those at level numbers 02 through 49) need not be unique if they can be made unique by qualification or if there are no references to them elsewhere in the program.

Screen-names defined in the Screen Section do not represent data items, and they can be referred to elsewhere in the program only in ACCEPT and DISPLAY statements.

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