Improved apparatus for specifying and resolving addresses of operands in a digital data processing system. Instructions executed by the system are contained in procedures. Addresses are calculated using a set of architectural base addresses. Operands are represented in the instructions by means of names. The names include immediate names, which directly specify one of the architectural base registers and a displacement, and table names, which specify a name table entry in a name table associated with the procedure. The name table entry specifies how the address of the operand represented by the table name may be derived using the architectural base addresses and information contained in the name table. Each name table entry includes a basic name table entry. The basic name table entry contains a base source specifier and a base or displacement specifier. The base source specifier specifies either one of the architectural base addresses as a base address or that the base address is not one of the architectural base addresses. In the former case, the base or displacement specifier specifies a displacement; in the latter, it contains an immediate name or a table name specifying another name table entry in the name table and the base address is derived using the immediate name or table name. Calculation of addresses is performed by name processing apparatus which is responsive to the base source specifier and the base or displacement specifier.