On 6/2/2014 8:01 AM, Skip Robinson wrote:
Early in my career I developed a habit when writing ASM code. In 'working storage', code DS/DC fields in this order unless some other structural sequence is required: double words first, then full words, half words, and finally character (C or X) fields of whatever length.
These days, fields at the "top" of a data area (i.e., lowest positive addresses for base register coverage) tend to be those that must be accessed via instructions that support only 12-bit displacements, e.g. MVC. Fields referenced by instructions with 20-bit displacements (e.g., L can be replaced with LY, LLGT, LLGF, LGF, etc.) can appear much, much further away or even in a negative direction (though I have yet to leverage that) from the origin of the data area.
-- Edward E Jaffe Phoenix Software International, Inc 831 Parkview Drive North El Segundo, CA 90245 http://www.phoenixsoftware.com/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
