An accumulator is a register for short-term, intermediate storage of arithmetic and logic data in a computer's CPU (central processing unit). The term "accumulator" is rarely used in reference to contemporary CPUs, having been replaced around the turn of the millennium by the term "register." In a modern computers, any register can function as an accumulator.
The most elementary use for an accumulator is adding a sequence of numbers. The numerical value in the accumulator increases as each number is added, exactly as it happens in a simple desktop calculator (but much faster, of course). Once the sum has been determined, it is written to the main memory or to another register.
The term "accumulator" is used in a wide variety of noncomputing applications and activities, such as electrical engineering (an energy storage device such as a rechargeable battery or ultracapacitor), hydraulics (a mechanical energy storage device), in stock trading (a contract or agreement), and even in gambling (a parlay bet).
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