Define computer architecture, computer organization, CPU and ALU.

Computer Architecture:

In computer science and engineering,computer architecture refers to specification of the relationship between different hardware components of a computer system. It may also refer to the practical art of defining the structure and relationship of the subcomponents of a computer. Computer architecture is concerned with all aspects of the design and organization of the central processing unit and the integration of the CPU into the computer system itself.

For example, at a high level, computer architecture is concerned with how the central processing unit (CPU) acts and how it accesses computer memory.

Computer Organization:

Computer organization refers to the operational units and their interconnections that realize the architectural specifications.Organization, is the implementation of computer system, in terms of its interconnection of functional units : CPU, memory, bus and I/O devices.So, organization of a computer is the implementation ofits architecture, but tailored to fit the intended price and performance measures.

Central processing unit (CPU):

The part of the computer that executes program instructions is known as the processor or central processing unit (CPU). In a microcomputer, the CPU is on a single electronic component, the microprocessor chip, within the system unit or system cabinet. This is principal part of any digital computer system, generally composed of control unit, and arithmetic-logic unit the ‘heart’ of the computer. It constitutes the physical heart of the entire computer system.

Arithmetic-Logic Unit (ALU) :

Arithmetic-Logic Unit usually called the ALU is a digital circuit that performs two types of operations - arithmetic and logical. Arithmetic operations are the fundamental mathematical operations consisting of addition, subtraction, multiplication and division. The ALU is a fundamental building block of the central processing unit of a computer.

Why we study the computer architecture?

• Design better programs, including system software such as compilers, operating systems, and device drivers. 
• Optimize program behavior.
• Evaluate (benchmark) computer system performance.
• Understand time, space, and price tradeoffs.