Search results
Results from the WOW.Com Content Network
The basic unit of digital storage is a bit, storing a single 0 or 1. Many common instruction set architectures can address more than 8 bits of data at a time. For example, 32-bit x86 processors have 32-bit general-purpose registers and can handle 32-bit (4-byte) data in single instructions. However, data in memory may be of various lengths.
Most modern computers are byte-addressable. Each address identifies a single byte of storage. Data larger than a single byte may be stored in a sequence of consecutive addresses. There exist word-addressable computers, where the minimal addressable storage unit is exactly the processor's word.
The size of the minimum addressable unit of memory can have complex trade-offs. Using a larger MAU allows the same amount of memory to be covered with a smaller address, which can substantially decrease the memory requirements of a program. However, using a smaller MAU makes it easier to work efficiently with small items of data.
Location-addressable Each individually accessible unit of information in storage is selected with its numerical memory address. In modern computers, location-addressable storage usually limits to primary storage, accessed internally by computer programs, since location-addressability is very efficient, but burdensome for humans. File addressable
(A few computers have used bit resolution.) If the unit is a word, then a larger amount of memory can be accessed using an address of a given size at the cost of added complexity to access individual characters. On the other hand, if the unit is a byte, then individual characters can be addressed (i.e. selected during the memory operation).
The EEPROM is memory-mapped in some devices; in others, it is not directly addressable and is instead accessed through address, data and control I/O registers. The general purpose registers, the status register and some I/O registers are bit-addressable, with bit 0 being the least significant and bit 7 the most significant.
If the paging unit is enabled, addresses in a segment are now virtual addresses, rather than physical addresses as they were on the 80286. That is, the segment starting address, the offset, and the final 32-bit address the segmentation unit derived by adding the two are all virtual (or logical) addresses when the paging unit is enabled.
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.