C vs C++

C++ is NOT a superset of C

C++ began as a fork of an early, pre-standardized C. However, the latest C++ is no longer a superset of the latest C.

Incompatibilities can be found in the wiki page: https://en.wikipedia.org/wiki/Compatibility_of_C_and_C%2B%2B

Release Cycles

• C++: every 3 years (C++98, C++03, C++11, C++14, C++17, C++20, C++23, C++26).
• C: updated much slower than C++ (C99, C11, C17, C23).

Procedural vs Object-oriented

• C++: object-oriented.
• C: procedural.

C headers vs C++ headers

• C Header: with .h suffix, e.g. <time.h>.
• C++ Header: with c prefix, e.g. <ctime>.

Differences:

• C does not have namespace. C headers will go into the global namespace, C++ style headers will go into std namespace.
• C headers don't have overloaded functions, e.g. C++ header <cmath> has overloaded sqrt functions for int and for float, but <math.h> only has one.

Some C headers do not have C++ version, e.g. <stdatomic.h>.

Takeaway: C++ program should avoid any C-Style headers <xxxx.h> if possible. (e.g. use cstdio instead of stdio.h):

#include <cstdio>

int main() {
  std::printf("Hello World\n");
}

Overloading / Overriding

• C++: supports both.
• C: does not support either.

Memory Management

• C++: new/delete and smart pointers.
• C: calloc() / malloc() and free().

Read more: C / C++ Memory Management

Security

• C++: supports encapsulation.
• C: data can be accessible by other entities.

Type cast / conversion

• C-style cast: conversion (int)3.5; cast (int)"hello".
• C++-style cast: static_cast, etc.

Strings

• C-style string: char*.
• C++-style string: std::string and std::string_view (since C++17).

Build tools

Both can use Clang and GCC.

They have different standard libraries:

• C: libc. Implementations: glibc (GNU C Library), musl(a lightweight implementation for Linux)
• C++: libc++ in Clang, libstdc++ in GCC.

Pointers and References

• C++: has both pointers and references.
• C: has pointers, but no references.

Functions in Structure

• C: doesn't allow function in struct.
• C++: allows function in struct.

Use Cases

C++ is more popular with applications level programming. C is more popular in low level systems programming.

• C is used in
  • operating systems, e.g. Linux Kernel (C++ is not allowed in Linux Kernel).
  • embedded systems.
  • compilers, libraries, interpreters of other languages: CPython (https://github.com/python/cpython)
  • graphics: Vulkan, OpenGL.
  • databases: PostgreSQL, Redis.
• C++
  • compilers, libraries, interpreters of other languages: OpenJDK, V8.
  • game engines: Unity, Unreal Engine.
  • databases: MongoDB, sqlite3.
  • server-side programming (used by many companies, like Google, Facebook, etc).
• many projects use both, e.g. Chrome, MySQL, etc.

Linus Torvalds’ views on C++

C++ is a horrible language. It’s made more horrible by the fact that a lot of substandard programmers use it, to the point where it’s much much easier to generate total and utter crap with it. Quite frankly, even if the choice of C were to do nothing but keep the C++ programmers out, that in itself would be a huge reason to use C.