The classic C-spec asks for half-adjust with H in column 53, where RPG IV
uses the (H) operation extender - the five-column classic opcode field has no
room for parentheses. Both spellings are honored, each in the layout that owns
it: a classic-layout source is read at column 53, and an RPG IV source has no
column 53 to read.
Column 53 rounds the result half away from zero, and applies wherever the (H)
extender does - Z-ADD, Z-SUB, ADD, SUB, MULT, DIV, SQRT and
XFOOT. It takes effect only when the intermediate result carries more decimal
positions than the result field; otherwise there is nothing to round and the
column is ignored. A blank column 53 truncates toward zero.
C Z-ADD7.5 A 51
C Z-ADDA B 30H B = 8 (rounded)
C Z-ADDA C 30 C = 7 (truncated)
C A MULT 1.55 D 30H D = 12 (11.625 rounded)
C A DIV 4 E 30H E = 2 (1.875 rounded)
As with the (H) extender, do not combine column 53 with a following MVR on a
DIV - MVR needs the truncated quotient's remainder.