WPbytes in sizeas compiled in the small model with Borland and Microsoft compilers with optimization on opt and off no opt. ASM ; Assembler subroutine to perform a bit checksum on the file ; opened on the passed-in handle. Stores the result in the ; passed-in checksum variable. Returns 1 for success, 0 for error.
Basic concept[ edit ] Mathematical operations often take place in a stepwise fashion, using the results from one operation as the input to the next. For instance, a manual calculation of a worker's weekly payroll might look something like: In early computers the number of hours would likely be held on a punch card and the pay rate in some other form of memory, perhaps a magnetic drum.
Once the multiplication is complete, the result needs to be placed somewhere. On a "drum machine" this would likely be back to the drum, an operation that takes considerable time.
And then the very next operation has to read that value back in, which introduces another considerable delay. Accumulators dramatically improve performance in systems like these by providing a scratchpad area where the results of one operation can be fed to the next one for little or no performance penalty.
In the example above, the basic weekly pay would be calculated and placed in the accumulator, which could then immediately be used by the income tax calculation. This removes one save and one read operation from the sequence, operations that generally took tens to hundreds of times as long as the multiplication itself.
Accumulator machines[ edit ] An accumulator machine, also called a 1-operand machineor a CPU with accumulator-based architecture, is a kind of CPU where, although it may have several registers, the CPU mostly stores the results of calculations in one special register, typically called "the accumulator".
Almost all early computers were accumulator machines with only the high-performance " supercomputers " having multiple registers. Then as mainframe systems gave way to microcomputersaccumulator architectures were again popular with the MOS being a notable example. Many 8-bit microcontrollers that are still popular as ofsuch as the PICmicro andare accumulator-based machines.
Modern CPUs are typically 2-operand or 3-operand machines. The additional operands specify which one of many general purpose registers also called "general purpose accumulators"  are used as the source and destination for calculations. These CPUs are not considered "accumulator machines". The characteristic which distinguishes one register as being the accumulator of a computer architecture is that the accumulator if the architecture were to have one would be used as an implicit operand for arithmetic instructions.
For instance, a CPU might have an instruction like: ADD memaddress that adds the value read from memory location memaddress to the value in the accumulator, placing the result back in the accumulator.
The accumulator is not identified in the instruction by a register number; it is implicit in the instruction and no other register can be specified in the instruction. Some architectures use a particular register as an accumulator in some instructions, but other instructions use register numbers for explicit operand specification.
History of the computer accumulator[ edit ] Any system that uses a single "memory" to store the result of multiple operations can be considered an accumulator.
Presper Eckert refers to even the earliest adding machines of Gottfried Leibniz and Blaise Pascal as accumulator-based systems. We will call such an organ an Accumulator. It is quite conventional in principle in past and present computing machines of the most varied types, e.
Just a few of the instructions are, for example with some modern interpretation: Clear accumulator and add number from memory location X Clear accumulator and subtract number from memory location X Add number copied from memory location X to the contents of the accumulator Subtract number copied from memory location X from the contents of the accumulator Clear accumulator and shift contents of register into accumulator No convention exists regarding the names for operations from registers to accumulator and from accumulator to registers.
Knuth's model has many other instructions as well. Notable accumulator-based computers[ edit ] Front panel of an IBM computer with lights displaying the accumulator and other registers The configuration of ENIAC had 20 accumulators, which could operate in parallel.
The IBMa decimal machine, had one 10 digit accumulator; the IBMa later, transistorized decimal machine had three accumulators. The bit PDP-8 was one of the first minicomputers to use accumulators, and inspired many later machines.
The Nova provided four accumulators, AC0-AC3, although AC2 and AC3 could also be used to provide offset addresses, tending towards more generality of usage for the registers. Early 4-bit and 8-bit microprocessors such as theand numerous others, typically had single accumulators.Write and execute an alp to Microprocessor to add, subtract and multiply two 16 bit unsigned numbers.
Store the result in extra segment Write and execute an alp to Microprocessor to divide a 32 bit unsigned numbers by a 16 bit unsigned number.
In a computer's central processing unit (), the accumulator is a register in which intermediate arithmetic and logic 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 main memory, perhaps only to be read right back again for use in the next operation.
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Theory Papers (Core) IT Digital Signal Processing. 3. 1. 4. IT Embedded System Design. 3. 1. 4. Electives (Select any Two. In this document, we study assembly language, the system for expressing the individual instructions that a computer should perform..
1. Background. We are actually concerned with two types of languages, assembly languages and machine languages. Definitions. A machine language encodes instructions as sequences of 0's and 1's; this binary encoding is what the computer's processor is built.
I am attempting to write a program in Assembly to take a plus or minus sign as the first input (deciding whether to plus or minus two numbers together) and then taking two 2 digit numbers and adding/subtracting and displaying the result.
A similar format can also be used when converting CAN messages into strings, depending on timberdesignmag.com-Identifiers with 11 bit (standard frames) are displayed with 3 digits.
Bit-Identifier (extended frames) are shown with 8 digits as in the example.