Learning C Language in 2019
Recently, I finally had some time to learn some C language. C code needs to be compiled into a binary executable file before it can be executed, so I configured the relevant environment for C/C++ according to the official tutorial of VS Code. Programming, debugging, and outputting results in one step makes the learning process more efficient.
I plan to start from The C Programming Language, and I typed the first example code in chapter one,
cc hello.c to compile it, I saw the error message:
The reason is that from the C99 standard, no type specifiers have been removed. The book uses the C89 standard, see The C89 Draft - 3.5.2 Type specifiers for details.
Well, now I will find out which standard
cc is using by executing the following command to view the pre-compilation macros defined by
The computer is Ubuntu 18.04, and the default standard used is C11.
There are approximately three commonly known C standards: c90 (or c89), c99, c11, which were released in 1990, 1999, and 2011, respectively. The original ANSI C standard (X3.159-1989) was approved in 1989 and released in 1990. It was later (in 1990) approved as an ISO standard (ISO/IEC 9899:1990). There is no technical difference between C89 and C90.
Well, let's start solving the problem. There are two options for the above code to work properly:
1. Modify the code according to the C11 standard
And it will output normally.
2. Use the C89 or C90 standard
In the Linux operating system,
cc is linked to
gcc through a soft link, so using
gcc in Linux has the same effect.