Browse Prior Art Database

Data List Addressing Mode

IP.com Disclosure Number: IPCOM000087467D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Davis, MI: AUTHOR [+5]

Abstract

This system provides improved efficiency of list-driven programs. Referring to Fig. 1, it includes a central processing unit (CPU) 1 with an associated channel la, storage 2, and a device attachment 3 incorporating a microprocessor 4 for the interconnection of an input/output device, such as a CRT display unit 5 having a keyboard 6 and display screen 9.

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Data List Addressing Mode

This system provides improved efficiency of list-driven programs. Referring to Fig. 1, it includes a central processing unit (CPU) 1 with an associated channel la, storage 2, and a device attachment 3 incorporating a microprocessor 4 for the interconnection of an input/output device, such as a CRT display unit 5 having a keyboard 6 and display screen 9.

A data processing system of this nature desirably includes a list-addressing mode that can significantly improve the efficiency of list-driven programs or subroutines. This addressing mode allows a program to directly address multiple discontiguous storage data lists using a single base register.

The instruction format for the list-addressing mode requires three elements per operand, as shown in Fig. 2.

Rb designates a General Purpose (GP) register which contains the storage address of a list of pointer variables (ADCONS).

D1 specifies a displacement in the list of pointer variables.

D2 specifies a displacement of a data element within a storage data list.

The values of D1 and D2 are considered to be unsigned binary integers. In execution, the contents of Rb are added to D1 and the resultant address is used to retrieve an element from the pointer variable list. The contents of this element, which is really a data list base, are then added to D2 to form the effective address of the target data element.

Fig. 3 shows the storage structure required to use the list-addressing mode.

Assuming th...