17 May
2020
17 May
'20
4:24 p.m.
On 5/16/20, Steffen Nurpmeso <steffen(a)sdaoden.eu> wrote:
Why was there no byte or "mem" type?
These days machine architecture has settled on the 8-bit byte as the
unit for addressing, but it wasn't always the case. The PDP-10
addressed memory in 36-bit units. The character manipulating
instructions could deal with a variety of different byte lengths: you
could store six 6-bit BCD characters per machine word, or five ASCII
7-bit characters (with a bit left over), or four 8-bit characters
(ASCII plus parity, with four bits left over), or four 9-bit
characters.
Regarding a "mem" type, take a look at BLISS. The only data type that
language has is the machine word.
+getfield(buf)
+char buf[];
+{
+ int j;
+ char c;
+
+ j = 0;
+ while((c = buf[j] = getc(iobuf)) >= 0)
+ if(c==':' || c=='\n') {
+ buf[j] =0;
+ return(1);
+ } else
+ j++;
+ return(0);
+}
so here the EOF was different and char was signed 7-bit it seems.
That makes perfect sense if you're dealing with ASCII, which is a
7-bit character set.
-Paul W.