C99 standard

C has many standards, C89, C99, C11 and here, we mainly focus on the C99 standard. Few of the new features included in C99 standard :

“<stdbool.h> header file include the bool data type and also added the true/false keywords was a little easier to use that in the program

So if you include that header file, you didn’t have to use _bool, you could just use bool and you could use true and false.

It was the revised standard for the C programming language.
It reflects the year that it came out.
It basically just refines and expands the capabilities of standard C, C89.
and it also has not been widely adapted, that’s one of the reasons we don’t focus on it too much.
It’s not not all popular – not all popular C compilers support it.
Of the compilers that do offer C99 support, most support only a subset of the standard.

So we don’t focus on many of the additions added for C99. We mainly focus on C89.

-> C89 is almost universally supported.