Single Lines In C Comments

[Marjamrob1]

When reading an older development book, I found this:

You may also hear multi-line comments being described as 'C-Style' comments because the /*...*/ is the only one available for creating comments in the C language.

However I have written C programs, that use "//" single line comments.

[ytk]

Originally, the only style for commenting in C was /* ... */. This is still the case in C89, which is traditionally known as ANSI-C. C99 added support for one line comments using //. If your book was written before the C99 standard was approved, it was correct at the time, and still is for older systems.

[Marjamrob1]

Ok, thank you, I understand now. I haven't actually ever used anything besides C99

[Madd the Sane]

// comments originally came from C++, IIRC.

[Marjamrob1]

Originally Posted by Madd the Sane

// comments originally came from C++, IIRC.

C++ when it was invented in 78 at Bell, or C++98

[chown33]

Originally Posted by Marjamrob1

C++ when it was invented in 78 at Bell, or C++98

Why does it matter?


There was a period of time when the C compilers used by Apple accepted // comments even though it wasn't in the ANSI/ISO C standard of the time. There was a command-line option for strict C conformance that would turn this off, so // was forbidden. IIRC, there was another option that would force strict compliance to the ISO C standard, EXCEPT that // comments were allowed. Other than as a historical footnote, none of this matters today, and hasn't since C99.

[ElectricSheep]

Originally Posted by Madd the Sane

// comments originally came from C++, IIRC.

They originally came from BCPL, which was also the first brace programming language. But, this is just esoteric trivia.

[Marjamrob1]

Originally Posted by chown33

Why does it matter?


There was a period of time when the C compilers used by Apple accepted // comments even though it wasn't in the ANSI/ISO C standard of the time. There was a command-line option for strict C conformance that would turn this off, so // was forbidden. IIRC, there was another option that would force strict compliance to the ISO C standard, EXCEPT that // comments were allowed. Other than as a historical footnote, none of this matters today, and hasn't since C99.

I was just curious but thank you.