Ferranti Mark 1 Instruction Codes

This page gives a summary of the instruction codes, first in logical order then in numerical order. In between is a key for the notation used. The 6-bit function codes are specified using the Base-32 notation used in the Programmer's Handbook (which go up from 0, 1, 2, 3, ... 63 in the form //, T/, /E, TE, ... T£ -- see note 3 for the Handbook). The link from the base-32 code goes to the appropriate part of the Handbook, although for many of the arithmetic codes there is no explicit specification, so the link is merely to the table of arithmetic instructions in the Handbook text.

The notation used in both summaries is that of the Handbook; the list in numerical order is essentially a copy of the text contained in the Handbook's appendix.

Note that the ' symbol is simply used to indicate a value that is reset by the instruction.

Summary Instruction Code (ordered logically)

Arithmetic Instructions (Key)
   A' = S±    T:    A' = 0
T/ A' = S+ TF A' = -S±
/S S' = L TK A' = 2S±
TC A' = A + S± /E S' = M
TI A' = A + S+ /A S' = M, M' = 0
TN A' = A - S± TA S' = L, A' = 0
/K D' = S± /U S' = L, L' = M, M' = 0
/C D' = S+ /J M' = M + S
/F A' = A + D S± /I L' = M, M' = L
/N A' = A + D S+ TR A' = A and S±
/D A' = A - D S± TD A' = A or S±
A' = A - D S+ TJ A' = A neq S±
/@ standardise
B-line Instructions Control Instructions
TT B' = s /P Uncond. direct jump
TL B' = B - s /Q Uncond. rel. jump
TZ s' = B /H A-cond. direct jump
TO # B' = s /M A-cond. rel. jump
TG # B' = B - s /T B-cond. direct jump
TB # s' = B /O B-cond. rel. jump
/G Stop if /G switch set
Miscellaneous /L Stop if /L switch set
/: S as mag. instr.
// H as mag. instr.
/Z S' = H
/W Random number generator
/R Sideways adder
/V Hoot
# Dummy
A The 80-bit Accumulator B One of the 8 20-bit B-lines
L The Least significant 40 bits of A The Multiplicand Register
The Most significant 40 bits of A H The 20-bit value on the console hand switches
S The contents of a 40-bit Store line
S± S explicitly treated using the plus-minus convention (the default)
S+ S explicitly treated using the plus convention
s The contents of a 20-bit Store line

Summary Instruction Code (ordered numerically)

//    H as mag. instr.     T/    A' = S+ (Key)
/E S' = M TE **
/@ standardise T@ **
/A S' = M, M' = 0 TA S' = L, A' = 0
/: S as mag. instr. T: A' = 0
/S S' = L TS **
/I L' = M, M' = L TI A' = A + S+
/U S' = L, L' = M, M' = 0 TU **
A' = A - D S+ A' = S±
/D A' = A - D S± TD A' = A or S±
/R Sideways adder TR A' = A and S±
/J M' = M + S TJ A' = A neq S±
/N A' = A + D S+ TN A' = A - S±
/F A' = A + D S± TF A' = -S±
/C D' = S+ TC A' = A + S±
/K D' = S± TK A' = 2S±
/T B-cond. direct jump TT B' = s
/Z S' = H TZ s' = B
/L Stop if /L switch set TL B' = B - s
/W Random number generator TW B' = B - s
/H A-cond. direct jump TH **
/Y ** TY **
/P Uncond. direct jump TP **
/Q Uncond. rel. jump TQ **
/O B-cond. rel. jump TO # B' = s
/B ** TB # s' = B
/G Stop if /G switch set TG # B' = B - s
/" ** T" # B' = B - s
/M A-cond. rel. jump TM # (B-exceptional
/X ** TX #     instructions)
/V Hoot TV #
** # Dummy

Notes on the numerically ordered list