What kinds of errors are discovered by the compiler?

Syntax errors occur when the code written by the programmer does not follow the rules and structure of the programming language. These rules are known as the syntax of the language. For instance, if a programmer forgets to close a bracket or include a necessary symbol, like a semicolon, then a syntax error occurs. The compiler is effective at catching syntax errors since it ensures the code it processes adheres to the specific rules and structure of the programming language.

Type errors occur when the programmer attempts to perform an operation on a data type that is not allowed by the programming language. For example, trying to divide a string value by an integer value would result in a type error. The compiler can detect type errors by checking the data types used in expressions and ensuring that they are compatible with the expected operation.

Scope errors are caused when a programmer attempts to access a variable, function, or object outside of its defined scope. Scope refers to the region of the program where a specific entity can be accessed. For instance, if a programmer tries to use a variable that is declared inside a function from another function, a scope error will occur. The compiler is responsible for enforcing the rules of scoping in the programming language and can detect scope errors by performing scope analysis.

Declaration errors occur when a programmer uses an undeclared variable, function, or object in their code. In most programming languages, variables, functions, and objects must be declared before they can be used in the code. For example, if a programmer attempts to use a variable before it has been declared or initialized, the compiler will catch this error during the compilation process.

Unreachable code refers to portions of a program that can never be executed under any circumstances. This could happen when a programmer includes code after a return statement or within a conditional branch that will never be true. The compiler can detect unreachable code during the compilation process, as it evaluates the program's control flow and identifies parts that will never be executed. To summarize, the compiler detects various kinds of errors, including syntax errors, type errors, scope errors, declaration errors, and unreachable code errors. By identifying these errors during the compilation process, the compiler helps to ensure that the final executable program is free of many common programming mistakes.