Here's a step-by-step breakdown of how an interpreter would execute the provided Python code:

1. Lexical Analysis: The interpreter reads the code and identifies the tokens: x, =, 5, y, =, x, +, 2, print, (, y, ).
2. Syntax Analysis: The tokens are parsed to create an abstract syntax tree (AST). The AST represents the program's structure, showing the assignments and the print statement. The parser verifies that the syntax is correct (e.g., assignment statements have the correct structure).
3. Semantic Analysis: The interpreter performs semantic checks. It checks that x and y are defined before being used. It also checks that the + operator is used with compatible operands (integers in this case). Type checking ensures that the assignment of 5 to x and the result of x + 2 to y are valid.
4. Execution:

   • The interpreter first executes x = 5. It creates a variable x and assigns the value 5 to it.
   • Next, it executes y = x + 2. It retrieves the value of x (which is 5), adds 2 to it (resulting in 7), and assigns the value 7 to the variable y.
   • Finally, it executes print(y). It retrieves the value of y (which is 7) and instructs the operating system to display the value 7 on the console.

An interpreter executes a program line by line. Unlike a compiler, which translates the entire source code into machine code before execution, an interpreter reads a statement, analyzes it, and then executes it immediately. This process is repeated for each statement in the program.

The key steps involved are:

• Lexical Analysis (Scanning): The interpreter reads the source code and breaks it down into a stream of tokens. Tokens are the basic building blocks of the language, such as keywords, identifiers, operators, and literals.
• Syntax Analysis (Parsing): The tokens are then checked for grammatical correctness according to the language's syntax rules. This involves building a parse tree or abstract syntax tree (AST) to represent the program's structure. Syntax errors are detected at this stage.
• Semantic Analysis: The interpreter checks the meaning of the program. This includes type checking, ensuring that variables are used correctly and that operations are valid. Semantic errors are identified here.
• Execution: The interpreter then executes the program's instructions represented by the AST. This might involve allocating memory, performing calculations, and interacting with the operating system.

Because the translation and execution happen concurrently, interpreters are generally easier to develop and debug than compilers. However, they are typically slower than compiled programs because each line of code must be re-analyzed and re-executed every time the program runs.

A compiler translates the entire source code into machine code at once. The resulting executable file can then be run independently. An interpreter, on the other hand, translates and executes the source code line by line.

Compiler Advantages:

• Speed: Compiled programs generally run faster because the translation is done beforehand.
• Optimization: Compilers can perform extensive optimizations during the compilation process.
• Independent Execution: The compiled executable can be run without the need for the compiler.

Compiler Disadvantages:

• Platform Dependence: The compiled executable is typically specific to the target platform.
• Debugging: Debugging can be more challenging as errors are often reported during compilation.

Examples: C, C++, Java (compiles to bytecode, then interpreted by the JVM)

Interpreter Advantages:

• Portability: Interpreted languages are generally more portable as they can run on any platform with an interpreter.
• Debugging: Debugging is often easier as errors are reported line by line during execution.
• Dynamic Typing: Interpreted languages often support dynamic typing, which can simplify development.

Interpreter Disadvantages:

• Speed: Interpreted programs generally run slower because the translation happens during execution.
• Less Optimization: Interpreters typically perform less optimization than compilers.

Examples: Python, JavaScript, Ruby