1. A method of executing a program with a computer system that supports mutually different categories of instruction types, the program containing a particular instruction with a particular symbolic reference to operand data, the method comprising providing a symbol table containing information for resolving symbolic references in instructions from any of the categories; providing groups of memory locations, each group being assigned to a respective one of the categories of instructions, each group for storing symbolic reference-result associations, the result of the association having resulted from resolving the symbolic reference of the association for an instruction of the category of instructions to which the group is assigned; executing the particular instruction, said executing comprising consulting the group assigned to the category to which the particular instruction belongs, to determine whether that group contains an association for the particular symbolic reference and, if there is such an association, using the result from the association as operand data for executing the particular instruction and, if there is no such association, resolving the particular symbolic reference by means of the symbol table, using the result from said resolving as the operand data for executing the particular instruction and storing an association between the symbolic reference and the result of said resolving in the group assigned to the category of the particular instruction.