ALU’s tasks and their suitable subcomponents:
Addition and subtraction
these two tasks are carried out by constructs of logic gates, such as half adders and full adders. While they may be termed ''adders'', with the aid of they can also carry out subtraction via use of inverters and ''two''s complement'' arithmetic.
The topic of logic gates is too exclusive and detailed to be covered in full here. Many resources survive on the internet and elsewhere relating to this topic, though, so it is recommended that you read further into the areas outlined above to aid with your learning.
Multiplication and division
in most modern processors, the multiplication and division of integer values is controlled by particular floating-point hardware within the CPU. previous processors used either additional chips known as math’s co-processors, or used a completely different method to perform the task.
Logical tests
further logic gates are used within the ALU to perform a number of different logical tests, as well as seeing if an operation produces a result of zero. Mainly of these logical tests are used to then change the values stored in the flag register, so that they may be checked later by separate operations or instructions. Others produce a result which is then stored, and used later in additional processing.
Comparison
Comparison operations contrast values in order to determine such things as whether one number is greater than, less than or equal to another. These operations can be performed by subtraction of one of the numbers from the other, and as such can be handled by the aforesaid logic gates. Though, it is not strictly necessary for the result of the calculation to be stored in this example. The amount by which the values differ is not required. In its place, the appropriate status flags in the flag register are set and checked to find out the result of the operation.
Bit shifting
Shifting operations move bits left or right inside a word, with different operations filling the gaps created in different ways. This is completed via the use of a shift register, which uses pulses from the clock in the control unit to trigger a chain reaction of movement across the bits that make up the word. Once more, this is a quite complicated logical procedure, and additionally reading may aid your understanding.