Register Types in the PC
A register is a portable, self-contained area accessible to the central processing unit of a personal computer. Most register units consist of some special hardware components and can only be read or written-to, and normally consist of an adjustable number of stored instructions. Instructions for execution are placed in immediate memory at the start of each workstation call. In some cases, instructions are stored in long-term memory (LTR) at the start of each workstation call. The register functions as a sort of log book, recording each input/output transaction as it happens. It is vitally important to save a register file, which contains all the crucial information regarding a particular system or application.
An accumulator is a device that stores and retrieves information into a register, for use in instructions to the CPU. As the name implies, accumulators are used in all forms of register operations. The more general function of an accumulator is to store a fraction of a digit; generally, the accumulator stores from one to eight zeros. The accumulator is one of the oldest form of computers, dating from the typewriter, and eventually replaced the punched paper cartridge. In addition to storing a finite number of zeros, accumulators also store a fraction of a digit, which can be executed as an instruction.
One of the earliest types of registers were simple memory registers used to record simple data. Modern day registers consist of both hardware and software and are accessed through a specific set of instructions. Modern processors can execute instructions into both local and external registers. In the early years of computers, registers used an address bus, with the CPU communicating information between internal registers and external registers. Address bus technology has evolved over the years, replacing the simple memory registers with microprocessors and specialized control queues.
A microprocessor assembles instructions to form machine instructions and executes them on the personal computer. Instructions are executed within a context, which consists of a single machine word or block of memory. The context can be a segment of memory or a complete program context, depending upon the instruction being executed. Instructions can reference any register, data register, or memory location. An instruction is an instruction to run a specific program, stop execution, or return to the programmer.
Standard output and input register, together with special purpose interrupts, are hardware components that provide information to the processor for executing instructions. The majority of today’s personal computer models include the Intel x86-based register architecture, which predates the use of MMU (ormacy masking) technology by the PC architectures of AMD, MIPS, pci, AGP, and IDS. MMU is an acronym for memory mapped interface, and refers to the PCI bus, ISA bus, or other chip on the motherboard that controls the allocation of memory addresses to different programs and users.
The stack pointer and instruction pointer are two of the most used registers. Stack pointer tracks the current location of the program counter, which is used to retrieve instructions as they are executed by the CPU. The stack pointer is also the origin of many errors that occur in the PC. The PC actually begins at address 0, where it continues to add instructions to the instruction pointer and continue from there.