The Key Differences Between C and C++

As a programmer you’ve likely encountered both C and C++ at some point. While the two languages share syntax and semantics, they differ in some important ways. In this article, we’ll dive into the key differences between C and C++ to help you understand when each language is better suited for a task.

A Brief History

First, a quick history lesson. C was developed in the 1970s by Dennis Ritchie at Bell Labs. It was designed as a general-purpose programming language suitable for systems programming tasks.

C++ was developed in the 1980s by Bjarne Stroustrup at Bell Labs as an extension of C. Stroustrup added object-oriented programming features like classes to C and named the new language “C with Classes.” This was eventually renamed C++.

So in essence, C++ is an extension of C with OOP features. However, over the years C++ has evolved to be quite distinct from C with many more advanced features.

Comparing C and C++

Now let’s get into the key differences between these languages:

Object-Oriented Programming

The most significant difference is that C is a procedural programming language while C++ supports both procedural and object-oriented programming.

C does not have concepts like classes, inheritance, polymorphism that are fundamental to object-oriented programming. C++ has all of these features and allows you to architect your program around objects interacting with each other.

Memory Management

In C, memory management is done manually by the programmer. You have to allocate and free memory by calling malloc() and free().

C++ abstracts a lot of these lower-level details through features like references, constructors, destructors, and smart pointers. Most of the time, you don’t have to manually allocate and free memory like in C.

Run-time Type Checking

C does not support run-time type checking. This means that type errors may only show up at runtime leading to unexpected behavior or program crashes.

C++ has stronger type checking in general. It also has features like RTTI (run-time type information) to do type checking at runtime. This improves type safety.

Standard Library

C++ has a much larger standard library compared to C. The C++ standard library includes containers, algorithms, iterators, utilities, and other data structures.

The C standard library is smaller and provides more basic features for I/O, string handling, mathematics, memory allocation, and manipulation.

Type System

C has basic types like int, float, char along with modifiers like unsigned, short, long.

C++ supports all C types but also has bool, void, wchar_t, auto, and strongly typed enumerations. C++ also has const and volatile type qualifiers.

Namespaces

C does not have namespaces. All identifiers need unique names across the entire program. This causes naming collisions with large programs.

C++ has namespaces allowing related identifiers like classes, objects, functions to be grouped together. This modules the code and avoids naming collisions.

Function Overloading

Function overloading is allowed in C++ but not in C. Overloaded functions have the same name but different parameters.

Exceptions

C does not have built-in exception handling. We have to rely on old techniques like error return values to indicate errors.

C++ has exception handling using the try, catch, throw keywords. Exceptions provide a structured way of handling errors or unusual conditions in a program.

Templates/Generics

C does not have templates or generics. There is no way to create reusable code that works for different data types.

C++ has templates that allow code reuse for different types. This is similar to generics in other languages like Java.

Threading and Concurrency

C does not have built-in facilities for threading and concurrency. We have to rely on platform-specific APIs for multi-threaded programs.

C++11 introduced threading support in the language itself with the std::thread library. C++ has all the tools for building concurrent programs.

References

C only has pointers to refer to memory addresses. C++ has references in addition to pointers. References are safer and easier to use than pointers.

Operator Overloading

Operator overloading allows redefining operators like +, -, *, / to work with user-defined types. C does not support this while C++ does.

Preprocessor

The C preprocessor is limited compared to the C++ preprocessor which has stronger macros and better error checking.

Performance

C is generally considered to have better performance than C++. C++ has some overhead from OOP features like inheritance and polymorphism. However, a well-written C++ program can match C performance.

Compilation Model

C uses a single-pass compilation model while C++ uses a multi-pass model. C++ needs multiple steps like parsing, instantiation, compilation, linking. This makes the compilation process more complex.

Standards Support

The latest ISO standard for C is C11 released in 2011. C++ has better standards support with regular updates. The latest C++ standard is C++20 released in 2020.

When to Use C vs C++

Given the differences discussed above, here are some general guidelines on when to use each language:

• Use C for lower-level system programming tasks like operating system kernels, device drivers, embedded systems.
• Use C when you need tight control over memory usage and hardware resources.
• Use C for portable code since it has minimal platform dependencies.
• Use C++ for application development to leverage OOP features.
• Use C++ when hardware resources are abundant and performance isn’t the main priority.
• Use C++ for large, complex projects that need object-oriented design.
• Use C++ for generic, reusable code using templates.
• Use C++ when reliability and type safety are critical.

Of course, there are always exceptions to these guidelines. For example, you can write object-oriented code in C and procedural code in C++. But in general, remembering these broad use cases can help decide which language to reach for.

Similarities Between C and C++

Despite the differences, C and C++ still share many common features given C++’s heritage as an extension of C:

• Similar syntax including curly braces to denote blocks.
• Control constructs like if, else, while, for are identical.
• The preprocessor works similarly with macros, file inclusion, conditional compilation.
• Comments styles are the same – /* */ for multi-line and // for single-line.
• Common data types like int, char, float, structures.
• Undefined and unspecified behavior concepts.
• Pointers and arrays work analogously.
• Fundamentals like variables, functions, scope, arrays are all similar.

This shared DNA means that it is easy to transition from C to C++. A C programmer can quickly be productive with C++.

Key Takeaways

• C is a procedural language while C++ supports both procedural and object-oriented programming.
• C++ has more features like classes, exceptions, templates that C lacks.
• C++ has a larger standard library compared to C.
• C is generally used for lower-level system programming.
• C++ is generally used for application development and complex projects.
• Many core syntax and concepts are still similar between the two languages.