Editing Random-access machine (section)

=== Register-to-register ("read-modify-write") model of Cook and Reckhow (1973) ===
The commonly encountered Cook and Rechkow model is a bit like the ternary-register Malzek model (written with Knuth mnemonics{{spaced ndash}}the original instructions had no mnemonics excepting TRA, Read, Print).

:*<code> LOAD ( C, r<sub>d</sub> ) ; C → r<sub>d</sub></code>, C is any integer
:: Example: <code>LOAD ( 0, 5 )</code> will clear register 5.
:*<code> ADD ( r<sub>s1</sub>, r<sub>s2</sub>, r<sub>d</sub>  ) ; [r<sub>s1</sub>] + [r<sub>s2</sub>] → r<sub>d</sub></code>, the registers can be the same or different;
::Example: <code>ADD ( A, A, A )</code> will double the contents of register A.
:*<code> SUB ( r<sub>s1</sub>, r<sub>s2</sub>, r<sub>d</sub> ) ; [r<sub>s1</sub>] - [r<sub>s2</sub>] → r<sub>d</sub></code>, the registers can be the same or different:
::Example: <code>SUB ( 3, 3, 3 )</code> will clear register 3.
:*<code> COPY ( i, r<sub>p</sub>, d, r<sub>d</sub> ) ; [[r<sub>p</sub>] ] →  r<sub>d</sub></code>, Indirectly copy the contents of the source-register pointed to by pointer-register r<sub>p</sub> into the destination register.
:*<code> COPY ( d, r<sub>s</sub>, i, r<sub>p</sub> ) ; [r<sub>s</sub>] → [r<sub>p</sub>]</code>. Copy the contents of source register r<sub>s</sub> into the destination-register pointed to by the pointer-register r<sub>p</sub>.
:*<code> JNZ ( r, I<sub>z</sub> ) ;</code> Conditional jump if [r] is positive; i.e. IF [r] > 0 THEN jump to instruction z else continue in sequence (Cook and Reckhow call this: "TRAnsfer control to line m if Xj > 0")
:*<code> READ ( r<sub>d</sub> ) ;</code> copy "the input" into destination register r<sub>d</sub>
:*<code> PRINT ( r<sub>s</sub> ) ;</code> copy the contents of source register r<sub>s</sub> to "the output."