Programming instructions

APPENDIX 4
PDP-4 Assembly Program
The more important characteristics of the PDP-4 Assembly Program are
mentioned briefly here to provide the background necessary to understand
the programming examples in this manual. The program and its complete
description are furnished to purchasers of PDP-4.
CHARACTER SET: The character set includes digits 0 through 9, letters
a through z, and the following punctuation characters:
Punctation Characters
Meaning
+ plus
add values
-
minus
subtract values
A space add values
A and combine values by logical AND
V or combine values by inclusive OR
( left parenthesis enclose constant word
1
right parenthesis
enclose constant word
. period
has value of current address
, comma assign address tag
= equals sign assign symbol on left of =
$ irikge return
begin comments; set current address
termination character
termination character
- overbar variable indicator
The characters A , $ , and 4 are nonprinting.
NUMBERS: Any sequence of digits delimited on the left and right by a
punctuation character.
SYMBOLS: Any sequence of alphanumeric characters, the first of which
must be a letter. Symbols are identified by the first six characters only.
‘Value symbols’ are those symbols which have a numerical value assigned
to them, either in the permanent symbol table, or during assembly. Value
symbols may be assigned by the use of a comma, indicating the symb
rr
I
to the left of the comma is an address tag; or by an equals sign, indicati g
the symbol to the left of the equals sign is to be assigned the value of the
word to the right of the equals sign.
Example: a, dzm 100
b= -1
c=a+b
67