IBM 5280 Distributed Data System - Index of

BR100BR101L..------16-Bit Address~-----------Page Number (0 to 3)Addressing through a System TableFormat and tables stored in the common area are available to any partition. When asource programspecifies that the format or table is in the common area (with an.XTRN control statement), the format or table is assigned a system table indexthat is greater than a valid index for a table or format within the partition. Thefollowing chart shows the range for a system table index for data areas outside thepartition:TypeValidIndexValuesScreen format 256-512Edit format 128-254Data table 128-254For edit formats and data tables, the index is stored in one byte of the object codeinstruction. For screen formats, a bit is set in the object code for the enter instruction(hex CF) to indicate that the screen format is in the common area.CONSTANTSIn a source program, a constant can be specified (1) as a decimal, hexadecimal, orbinary value, (2) as a character, or (3) with a label that is equated to a value. In theobject code, any form of constant is stored in the object code as immediate data.The following list shows the kinds of constants that are used in a source program.• Data set number: The number of the current data set. The number can be anynumber from hexadecimal 1 to F and requires 4 bits of object code.• Length: The length of data being used by the instruction.• Displacement: The displacement into a data area; usually an optional parameterin a data movement instruction.• Mask: A pattern of bits used in skip operations. Each mask requires 8 bits.Object Code Instruction Format 137