Difference between Semantic error and logical error

Question

from some articles I read on general programming concept. I was made to know that "syntaxs are the formal rules that governs the construct of valid statement in a language" while "semantics are set of rules that give meaning to a statement of a language". from the defination of semantics, I feel it is similar to logic, if not, then please I want to know the difference between logical error and semantic error?

Answer 1

There seems to be lot of confusion around the definition of these terms, but here's my understanding:

Syntax relate to spelling and grammar.

Logic relate to program flow.

Semantics relate to meaning and context.

If the code fails to execute due to typos, invalid names, a missing parenthesis or some other grammatical flaw, you have a syntax error.

If the syntax is correct but a piece of code is (inadvertently) never executed, operations are not done in the correct order, the operation itself is wrong or code is operating on the wrong data, you have a logical error. Using a wrong conditional operator is a common example, so is inadvertently creating an infinite loop or mixing up (valid) names of variables or functions.

If both your program logic and syntax is correct so the code runs as intended, but the result is still wrong: you likely have a semantic error. Confusing a metric input value for an imperial value will get you there. Nothing wrong with the program, except that miles and kilometres don't add up, so your area calculation throws out the wrong number. Having a race condition is another common example.