Programming instructions

APPENDIX 3
Read-h Mode Sequence
The initial data input to PDP-4 is made using the keys and switches on the
Operator Console. A small program read in manually can be used to read
in a somewhat larger program from perforated tape. An example of such
a routine is given below. It can also be used to read in other programs from
perforated tape.
READ-IN LOADER
The purpose of the read-in loader is to load programs punched in “read-in
mode,” such as the block format loader described below. The read-in
loader must be loaded by means of the console toggle switches. It loads
tapes of the following format:
dac A
c(A)
dac B
4%
imp Y
dummy word
Read-in mode tapes consist of word pairs giving a dac into an address,
followed by the contents of that address. They are terminated by a jmp to
the program followed by a dummy word (e.g., 0).
To load a read-in mode tape, place the tape in the reader, set the ADDRESS
switches to 7770, and press START.
LOCATION OCTAL CODE
77621
0 r,
77631 700101
77641 607763
77651 700112
77661 700144
77671 627762
77701 700144 go,
77711 107762 g,
77721 47775
77731 407775
77741 107762
77751 0 out,
77761
607771
MNEMONIC
0
rsf
jmp. - 1
rrb
rsb
jmp i r
rsb
jms r
dac out
xct out
jms r
0
imp g
65
REMARKS
/read one binary word
/wait for word to come in
/read buffer
/read another word
/exit subroutine
/enter here, start reader going
/get next binary word
/execute control word
/get data word
/store data word
/continue