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See (p1,realdom) for information about the use of this key. All calls to the DOMAIN_TOOL are prompt. See (p1,synergism) about why domain tools are non fundamental {not needed in theory}.

DOMAIN_TOOL(0;NK==>c;DK) produces a domain key that designates the node designated by the node key NK. c is zero if NK is a node key and −1 otherwise. The databyte of DK is 0.

{Rights Amplification}If (E is a start key and n is 1, or E is a return or fault key and n is 2, or E is a domain key and n is 3) and E's brand {C0 of E's domain} is B then DOMAIN_TOOL(n;E,B ==> b;N) returns the databyte of E in b and returns a node key {with 0 databyte} to E's domain root. Otherwise the call returns −1 in b and DK(0) in N.

See (p3,res-ex) about why restart keys are excluded.
(Order codes 5, 6, 7, 9, 10 & 11) If (S is a segment key with a segment keeper key and the no-call bit off and n is 4, or S is a meter key and n is 8) and S's keeper key is (a start key and m is 1, or a return or fault key and m is 2, or a domain key and m is 3) and B is the brand of S's keeper, then DOMAIN_TOOL(n+m;S,B ==> c+256*s;N) will return a node key N to the node designated by S, c is the databyte from S, s is the slot number in node S which holds the keeper key, N has the same databyte as S. Otherwise c=−1 and s=0 and N is DK(0). The databyte of a meter key is 0. This function of the domain tool does not allow the tool holder to discover information that could otherwise be considered safely hidden.
Fine print: If the segment or meter node is one of the nodes of the jumper's domain, c=−1 and s=0.

See (scne) concerning exclusion of restart keys.

{ni}I propose that if S is a segment key with the no-call bit on then a sense key to the node be returned.

DOMAIN_TOOL(kt;==>c;) puts X'0109' in c.

See (p1,realdom) for reasons for restricting this entry. See also (p2,dc) and ((p1,worsejump) SC = 51).