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

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.

The compilation process transforms human-readable source code into machine-executable code. The key stages are:

• Lexical Analysis (Scanning): This stage reads the source code character by character and groups them into tokens. Tokens represent basic building blocks like keywords, identifiers, operators, and literals. The output is a stream of tokens.
• Syntax Analysis (Parsing): The tokens are then fed into a parser, which checks if the sequence of tokens conforms to the grammar of the programming language. This creates an Abstract Syntax Tree (AST), a hierarchical representation of the program's structure. If syntax errors are detected, the compiler reports them.
• Semantic Analysis: This stage checks the meaning and consistency of the program. It performs type checking, ensuring that operations are performed on compatible data types. It also checks for undeclared variables and other semantic errors. The output is an annotated AST.
• Intermediate Code Generation: The annotated AST is translated into an intermediate representation (IR). This IR is platform-independent and simplifies optimization. Common IRs include three-address code or P-code.
• Code Optimization: The intermediate code is optimized to improve its efficiency, such as reducing code size or execution time. This can involve various techniques like constant folding, dead code elimination, and loop unrolling.
• Code Generation: The optimized intermediate code is translated into machine code specific to the target architecture. This involves allocating registers, generating instructions, and creating the executable file.

The final output is an executable program that can be run on the target platform.