Computers, Computer Science 1. (Processor) In a central processing unit, a register in which intermediate results are stored. Without an accumulator, it would be necessary to write the result of each calculation (addition, multiplication, shift, etc.) to main memory and read them back. Access to main memory is slower than access to the accumulator which usually has direct paths to and from the arithmetic and logic unit(ALU). 2. (Programming) A register, memory location or variable being used for arithmetic or logic (as opposed to addressing or a loop index), especially one being used to accumulate a sum or count of many items.