Memory address

In a computer using virtual memory, accessing the location corresponding to a memory address may involve many levels.

Reference to a specific memory location used at various levels by software and hardware.

- Memory address
In a computer using virtual memory, accessing the location corresponding to a memory address may involve many levels.

170 related topics

Relevance

Transistor count over time, demonstrating Moore's law

Processor register

Quickly accessible location available to a computer's processor.

Quickly accessible location available to a computer's processor.

Transistor count over time, demonstrating Moore's law

In computer architecture, registers are typically addressed by mechanisms other than main memory, but may in some cases be assigned a memory address e.g. DEC PDP-10, ICT 1900.

Virtual memory combines active RAM and inactive memory on DASD to form a large range of contiguous addresses.

Virtual memory

Memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very large memory".

Memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very large memory".

Virtual memory combines active RAM and inactive memory on DASD to form a large range of contiguous addresses.
The University of Manchester Atlas Computer was the first computer to feature true virtual memory.

The computer's operating system, using a combination of hardware and software, maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory.

Four PCI Express bus card slots (from top to 2nd bottom: ×4, ×16, ×1 and ×16), compared to a 32-bit conventional PCI bus card slot (very bottom)

Bus (computing)

Communication system that transfers data between components inside a computer, or between computers.

Communication system that transfers data between components inside a computer, or between computers.

Four PCI Express bus card slots (from top to 2nd bottom: ×4, ×16, ×1 and ×16), compared to a 32-bit conventional PCI bus card slot (very bottom)
Single system bus

A microprocessor conventionally is a single chip which has a number of electrical connections on its pins that can be used to select an "address" in the main memory and another set of pins to read and write the data stored at that location.

Machine language monitor in a W65C816S single-board computer, displaying code disassembly, as well as processor register and memory dumps.

Machine code

Any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit .

Any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit .

Machine language monitor in a W65C816S single-board computer, displaying code disassembly, as well as processor register and memory dumps.

While it is possible to write programs directly in machine code, managing individual bits and calculating numerical addresses and constants manually is tedious and error-prone.

Computer simulation, one of the main cross-computing methodologies.

Word (computer architecture)

Natural unit of data used by a particular processor design.

Natural unit of data used by a particular processor design.

Computer simulation, one of the main cross-computing methodologies.

The largest possible address size, used to designate a location in memory, is typically a hardware word (here, "hardware word" means the full-sized natural word of the processor, as opposed to any other definition used).

Diagram of relationship between the virtual and physical address spaces

Physical address

Diagram of relationship between the virtual and physical address spaces

In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a particular storage cell of main memory, or a register of memory-mapped I/O device.

1 GiB of SDRAM mounted in a computer. An example of primary storage.

Computer data storage

Technology consisting of computer components and recording media that are used to retain digital data.

Technology consisting of computer components and recording media that are used to retain digital data.

1 GiB of SDRAM mounted in a computer. An example of primary storage.
15 GB PATA hard disk drive (HDD) from 1999. When connected to a computer it serves as secondary storage.
160 GB SDLT tape cartridge, an example of off-line storage. When used within a robotic tape library, it is classified as tertiary storage instead.
Read/Write DVD drive with cradle for media extended
Various forms of storage, divided according to their distance from the central processing unit. The fundamental components of a general-purpose computer are arithmetic and logic unit, control circuitry, storage space, and input/output devices. Technology and capacity as in common home computers around 2005.
A hard disk drive (HDD) with protective cover removed
A large tape library, with tape cartridges placed on shelves in the front, and a robotic arm moving in the back. The visible height of the library is about 180 cm.
A 1 GiB module of laptop DDR2 RAM
S.M.A.R.T. software warning suggests impending hard drive failure
Error rate measurement on a DVD+R. The minor errors are correctable and within a healthy range.

The CPU firstly sends a number through an address bus, a number called memory address, that indicates the desired location of data.

The Commodore 64 was one of the most popular microcomputers of its era, and is the best-selling model of home computer of all time.

32-bit computing

32-bit microcomputers are microcomputers that use 32-bit microprocessors.

32-bit microcomputers are microcomputers that use 32-bit microprocessors.

The Commodore 64 was one of the most popular microcomputers of its era, and is the best-selling model of home computer of all time.

One important consequence is that a processor with 32-bit memory addresses can directly access at most 4 GiB of byte-addressable memory (though in practice the limit may be lower).

Block diagram of a basic computer with uniprocessor CPU. Black lines indicate data flow, whereas red lines indicate control flow. Arrows indicate the direction of flow.

8-bit computing

In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet).

In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet).

Block diagram of a basic computer with uniprocessor CPU. Black lines indicate data flow, whereas red lines indicate control flow. Arrows indicate the direction of flow.

Memory addresses (and thus address buses) for 8-bit CPUs are generally larger than 8-bit, usually 16-bit.

Block diagram of a basic computer with uniprocessor CPU. Black lines indicate data flow, whereas red lines indicate control flow. Arrows indicate the direction of flow.

64-bit computing

Block diagram of a basic computer with uniprocessor CPU. Black lines indicate data flow, whereas red lines indicate control flow. Arrows indicate the direction of flow.

In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide.