From: "Gerhard Postpischil" <[email protected]>
Sent: Tuesday, 30 August 2011 2:57 PM
On 8/29/2011 11:29 PM, Justin R. Bendich wrote:
Do any of you old-timers (e.g. Fairchild, Cole) know how the EDIT (ED)
instruction came to be the way it is? It's one of the original IBM 360
instructions. Has to be the most complicated of them. Did they have
microcode back then?
My understanding is that it was designed to meet business
specifications
Indeed it was.
It also designed to edit an entire line of (commercial) numbers.
However, it's also handy for the normal decimal output
of floating-point numbers (real and complex).
The EDMK instruction is even handier for normal decimal output
(both commercial and non-commercial)
because it facilitates the insertion of the sign before the most-significant
digit.
- setting R1 (EDMK) allows for easy insertion of
a $ or asterisk "protection" byte, and a sign after the numerics
provides for common commercial usage of a CR or - after the
number. Microcode was available on some machines. The design was
elegant, and simple to implement.
