What (who) is register addressing - definition

THE DIVISION OF COMPUTER'S PRIMARY MEMORY INTO SEGMENTS OR SECTIONS

Segmented memory; Segmented Addressing; Segmented address space; Segment register; Memory segment; Code segments; Text segments; Segmentation (memory); Segmented addressing; Segment (memory); Segment:offset addressing; Segment:offset; Segment:offset notation; Segment:offset addressing scheme; Segment:offset memory addressing

indirect address

ASPECT OF THE INSTRUCTION SET ARCHITECTURE IN MOST CENTRAL PROCESSING UNIT DESIGNS

Addressing modes; Indirect word; Address mode; Indirect address; Absolute coding; Absolute and relative coding; Indexed addressing; Indirect addressing; Relative coding; Effective address; Load Effective Address; Push Effective Address; Indirection bit; Indirection (computing); Special addressing modes for implementation of stacks; Conditional execution; Register indirect; Direct addressing; Address modes; Direct-addressing; Direct address (computing)

<processor> An addressing mode found in many processors' instruction sets where the instruction contains the address of a memory location which contains the address of the operand (the "effective address") or specifies a register which contains the effective address. In the first case (indirection via memory), accessing the operand requires two memory accesses - one to fetch the effective address and another to read or write the actual operand. Register indirect addressing requires only one memory access. An indirect address may be indicated in assembly language by an operand in parentheses, e.g. in Motorola 68000 assembly MOV D0,(A0) writes the contents of register D0 to the location pointed to by the address in register A0. Indirect addressing is often combined with pre- or post- increment or decrement addressing, allowing the address of the operand to be increased or decreased by one (or some specified number) either before or after using it. (1994-11-07)

addressing mode

ASPECT OF THE INSTRUCTION SET ARCHITECTURE IN MOST CENTRAL PROCESSING UNIT DESIGNS

1. <processor, programming> One of a set of methods for specifying the operand(s) for a machine code instruction. Different processors vary greatly in the number of addressing modes they provide. The more complex modes described below can usually be replaced with a short sequence of instructions using only simpler modes. The most common modes are "register" - the operand is stored in a specified register; "absolute" - the operand is stored at a specified memory address; and "immediate" - the operand is contained within the instruction. Most processors also have indirect addressing modes, e.g. "register indirect", "memory indirect" where the specified register or memory location does not contain the operand but contains its address, known as the "effective address". For an absolute addressing mode, the effective address is contained within the instruction. Indirect addressing modes often have options for pre- or post- increment or decrement, meaning that the register or memory location containing the effective address is incremented or decremented by some amount (either fixed or also specified in the instruction), either before or after the instruction is executed. These are very useful for stacks and for accessing blocks of data. Other variations form the effective address by adding together one or more registers and one or more constants which may themselves be direct or indirect. Such complex addressing modes are designed to support access to multidimensional arrays and arrays of data structures. The addressing mode may be "implicit" - the location of the operand is obvious from the particular instruction. This would be the case for an instruction that modified a particular control register in the CPU or, in a stack based processor where operands are always on the top of the stack. 2. In IBM System 370/XA the addressing mode bit controls the size of the effective address generated. When this bit is zero, the CPU is in the 24-bit addressing mode, and 24 bit instruction and operand effective addresses are generated. When this bit is one, the CPU is in the 31-bit addressing mode, and 31-bit instruction and operand effective addresses are generated. ["IBM System/370 Extended Architecture Principles of Operation", Chapter 5., 'Address Generation', BiModal Addressing]. (1995-03-30)

indirect addressing

ASPECT OF THE INSTRUCTION SET ARCHITECTURE IN MOST CENTRAL PROCESSING UNIT DESIGNS

indirect address

Wikipedia

Memory segmentation

Memory segmentation is an operating system memory management technique of division of a computer's primary memory into segments or sections. In a computer system using segmentation, a reference to a memory location includes a value that identifies a segment and an offset (memory location) within that segment. Segments or sections are also used in object files of compiled programs when they are linked together into a program image and when the image is loaded into memory.

Segments usually correspond to natural divisions of a program such as individual routines or data tables so segmentation is generally more visible to the programmer than paging alone. Segments may be created for program modules, or for classes of memory usage such as code and data segments. Certain segments may be shared between programs.

Segmentation was originally invented as a method by which system software could isolate software processes (tasks) and data they are using. It was intended to increase reliability of the systems running multiple processes simultaneously. In a x86-64 architecture it is considered legacy and most x86-64-based modern system software don't use memory segmentation. Instead they handle programs and their data by utilizing memory-paging which also serves as a way of memory protection. However most x86-64 implementations still support it for backward compatibility reasons.

https://en.wikipedia.org/wiki/Memory segmentation