Startec Startec - 1 year ago 236
C Question

Does C++ contain the entire C language?

I have read in tutorials that C++ contains the entire C programming language.

However I have also read, in places like this that

If you learn C++ you will eventually learn most of C with some differences between the languages that you will learn over time.

So my question is only this:

If I know C++ very well, will I eventually learn the "real" C language (without any "differences") because the full C90 language is included in C++11?

Answer Source

No, C++ is not a superset of the C language. While C++ contains a large part of C, there are subtle difference that can bite you badly where you least expect them. Here are some examples:

  • C does not require explicit conversion on assignment of void pointers to variables of concrete type.
  • C has different rules regarding const propagation.
  • C has something called the “implicit int rule,” which, although abolished with C99, appears some times and needs to be considered.
  • The C preprocessor has some features the C++ preprocessor does not have.
  • The C language has two styles of function definition, K&R-style and Stroustrup-style. C++ only has Stroustrup-style.
  • The lexing rules for C and C++ are different with neither being a subset of the other
  • C and C++ have different sets of reserved words. This can cause weird errors because an identifier is not allowed in the other language.
  • While C++ took almost all features from ANSI C (C89), many features were added to C in subsequent standard revisions that are not available in C++.
  • C++ has a different syntax, even for some parts that aren't new. For example, a ? b : c = d is a syntax error in C but parsed as a ? b : (c = d) in C++.
  • C guarantees that &*E is exactly identical to E, even if E is a null pointer. C++ has no such guarantee.
  • In C, a string literal initializing an array of characters can initialize an array that is at least as long as the string without the trailing \0 byte. (i.e. char foo[3] = "bar" is legal). In C++, the array has to be at least as long as the string including the trailing \0 byte.
  • In C, a character literal like 'A' has type int. In C++, it has type char.
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