In order to follow the examples in this chapter, the reader must have:

• A Linux-based system capable of compiling and executing C++17 (for example, Ubuntu 17.10+)
• GCC 7+
• CMake 3.6+
• An internet connection

To download all the code in this chapter, including the examples and code snippets, go to the following link: https://github.com/PacktPublishing/Hands-On-System-Programming-with-CPP/tree/master/Chapter02.

The C programming language is one of the oldest languages available. Unlike other higher-level languages, C is similar enough to assembly language programming, while still providing some high-level programming abstractions, that it has become a firm favorite among system, embedded, and kernel-level programmers alike.

Almost every major operating system is rooted in C. In addition, most higher-level languages, including C++, build upon C to provide their higher-level constructs, and therefore still require some of the components of the C standard.

The C standard is a huge standard that is managed by the International Organization for Standardization (ISO). We assume the reader has some basic knowledge of the C standard and how to write C code: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf.

For these reasons, the goal of this...

The C++ programming language (originally called C with Classes) was designed specifically to provide higher-level facilities than C, including better type safety and object-oriented programming, with system programming in mind. Specifically, C++ aims to provide the performance and efficiency of C programs, while still providing the features of higher-level languages.

Today, C++ is one of the most popular programming languages in the world, used in everything from avionics to banking.

Like the C standard, the C++ standard is huge and is managed by the ISO. We assume the reader has some basic knowledge of the C++ standard and how to write C code: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf.

For these reasons, the goal of this section is to discuss some topics that are discussed in lesser detail in other books, as well as portions...

The POSIX standard defines all of the functionality a POSIX-compliant operating system must implement. With respect to system programming, the POSIX standard defines the system call interface (that is, the APIs, not the ABIs) that the operating system must support.

Under the hood, most of the system-level APIs that C and C++ provide actually execute POSIX functions, or are POSIX functions themselves (as is this case with a lot of C library APIs). In fact, libc is generally considered to be a subset of the greater POSIX standard, while C++ leverages libc and POSIX to implement its higher-level APIs such as threading, memory management, error handling, file operations, and input/output. For more information, refer to https://ieeexplore.ieee.org/document/8277153/.

In this section, we will discuss some components of the POSIX standard that are relevant...

In this chapter, we learned about three different standards: C, C++, and POSIX. The C standard defines the popular C syntax, C-style program linking and execution, and the standard C libraries that provide cross-platform APIs to wrap an operating system's ABIs.

We also learned about the C++ standard, and how it defines the C++ syntax, program linking and execution, and the high-level C++ APIs that wrap underlying C and POSIX APIs to C++.

Finally, we saw how the POSIX standard provides additional APIs that go beyond C. These APIs include (but are not limited to) memory management, networking, and threading. In general, the POSIX standard defines all the standards needed for an application to perform its functions in a cross-platform way on any POSIX-compliant operating system.

The remainder of this book will focus on the APIs defined in these standards, and how they...

1. Is the C standard part of the POSIX standard? If so, name an API that is common to both standards.
2. What is the difference between the _start() and main() functions?
3. List one of the responsibilities of the C runtime?
4. Are global constructors executed before or after the main() function?
5. What is C++ name mangling, and why is it needed?
6. Name one difference between C and C++ program linking.
7. What is the difference between a pointer and a reference?

• https://www.packtpub.com/application-development/c17-example
• https://www.packtpub.com/application-development/getting-started-c17-programming-video