1. A method of compiling a knowledge base in an expert system which includes a computer having N registers including registers H, K, SH, and Ai (where i=1 to N-3 and N is an integer); a knowledge base including fact knowledge and rules, each rule having a condition part for specifying conditions applicable to said each rule and an execution part for specifying execution under application of said each rule, each fact knowledge including M attributes ATi (where i=1 to M and M is an integer) of any values, and said rules including a rule having a condition part for representing an attribute and an execution part for modifying a value of an attribute; a first memory storage for storing said knowledge base; a second memory storage for storing said compiler program for compiling said knowledge base into instruction sequences executable by said computer; a third memory storage for storing said instruction sequences compiled by said compiler program; an instantiation holding area for storing an instantiation generated by execution of said instruction sequences, said register K denoting a top address of said instantiation holding area; a first work area used by said compiler program; and a second work area used in execution of said instruction sequences, said register H denoting a top address of said second work area; said method comprising the steps of: (a) compiling fact knowledge having M attributes ATi (i=1 to M) into instruction sequences which transfer each i-th attribute ATi to a corresponding i-th register Ai (i=1 to M); (b) compiling an attribute ATi of fact knowledge referred to in a condition part of a rule into instruction sequences including: (b1) a pattern matching instruction sequence which compares the attribute ATi with a content of a corresponding register Ai, (b2) register transferring instructions which transfer a content of said register H to said register SH and a content of said register K to said register H, for adding an instantiation to said instantiation holding area, each instantiation comprising a combination of a rule and a fact knowledge which meets the condition part of said rule, (b3) instructions which generate said instantiation in said instantiation holding area, (b4) instructions which transfer a content of said register H to said register K, and a content of said register SH to said register H, and (b5) a fail instruction which branches to an instruction sequence of another condition part of another rule; (c) generating a fact management table comprising at an entry designated by a fact knowledge: (c1) a first address of an instruction sequence of condition parts of rules referring to said fact knowledge, and (c2) a second address of an instruction sequence of said fact knowledge; and (d) compiling an execution part of a rule which modifies an attribute ATi of a fact knowledge to instruction sequences including: (d1) a modify instruction which modifies said attribute ATi of said fact knowledge to a value, (d2) a delete instruction which deletes an instantiation containing said fact knowledge with an attribute ATi from said instantiation holding area, (d3) a transfer instruction sequence which transfers each of said attributes ATi of said fact knowledge modified by said instruction (d1) to a corresponding register Ai, said attributes AT1 being included in an instruction addressed by a second address of said fact management table indexed with an entry corresponding to said fact knowledge, and (d4) a jump instruction which branches to an instruction sequence of a condition part of a rule referring to said fact knowledge modified by said instruction (d1), a target address of said jump instruction being included in said first address of said fact management table indexed by an entry corresponding to said fact management table.