gbranden pushed a commit to branch master
in repository groff.
commit 7abe83b6fd9cf436e88944f57e1f0a738734ab8a
Author: G. Branden Robinson <[email protected]>
AuthorDate: Sun Aug 9 06:02:20 2026 -0500
PROBLEMS: Clarify antiquarian nerd point.
Only the _base_ PDP-11 instruction set lacked an integer modulus
instruction. The EIS feature offered one via the DIV instruction, which
stored the quotient to former member of a register pair, and the
remainder to the latter. This would have been close enough to a integer
modulus instruction for nroff and troff to use it, but there may have
been advantage in keeping the assembly versions of these programs
portable across the product line. (Or maybe the CSRC's PDP-11 didn't
have an EIS module at the time Ossanna wrote the relevant code.)
---
PROBLEMS | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/PROBLEMS b/PROBLEMS
index 2c657da70..8003a6078 100644
--- a/PROBLEMS
+++ b/PROBLEMS
@@ -198,8 +198,8 @@ or, if you want to be portable to older troff versions, as
follows:
(This defect may have arisen because nroff and troff were originally
written in PDP-11 assembly language and subsequently translated by hand
-to an early dialect of the C language. The PDP-11 instruction set had
-no integer modulus instruction.)
+to an early dialect of the C language. The base PDP-11 instruction set
+had no integer modulus instruction.)
----------------------------------------------------------------------
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