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In a computer's central processing unit (CPU), the accumulator is a register in which intermediate arithmetic logic unit results are stored.. Without a register like an accumulator, it would be necessary to write the result of each calculation (addition, multiplication, shift, etc.) to cache or main memory, perhaps only to be read right back again for use in the next operation.
In 1967, Fairchild introduced the first ALU-like device implemented as an integrated circuit, the Fairchild 3800, consisting of an eight-bit arithmetic unit with accumulator. It only supported adds and subtracts but no logic functions. [7] Full integrated-circuit ALUs soon emerged, including four-bit ALUs such as the Am2901 and 74181.
The hardware unit that performs the operation is known as a multiplier–accumulator (MAC unit); the operation itself is also often called a MAC or a MAD operation. The MAC operation modifies an accumulator a : a ← a + ( b × c ) {\displaystyle a\gets a+(b\times c)}
Here is a simple example of index register use in assembly language pseudo-code that sums a 100 entry array of 4-byte words: Clear_accumulator Load_index 400,index2 //load 4*array size into index register 2 (index2) loop_start : Add_word_to_accumulator array_start,index2 //Add to AC the word at the address (array_start + index2) Branch_and_decrement_if_index_not_zero loop_start,4,index2 //loop ...
A sample computer system, the Wombat 1, is provided with CPU Sim.It has the following registers: pc (program counter);acc (accumulator);ir (instruction register);mar (memory address register);
Folds can be regarded as consistently replacing the structural components of a data structure with functions and values. Lists, for example, are built up in many functional languages from two primitives: any list is either an empty list, commonly called nil ([]), or is constructed by prefixing an element in front of another list, creating what is called a cons node ( Cons(X1,Cons(X2,Cons ...
On an accumulator-based architecture machine, this may be a dedicated register. On a machine with multiple general-purpose registers , it may be a register that is reserved by convention, such as on the IBM System/360 through z/Architecture architecture and RISC architectures, or it may be a register that procedure call and return instructions ...
Registers are normally measured by the number of bits they can hold, for example, an 8-bit register, 32-bit register, 64-bit register, 128-bit register, or more.In some instruction sets, the registers can operate in various modes, breaking down their storage memory into smaller parts (32-bit into four 8-bit ones, for instance) to which multiple data (vector, or one-dimensional array of data ...