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Early C ?

I found this , from another post here

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about Early C, by Kernighan.

In the introduction it says.

"Disclaimer: This ``tutorial'' is presented as a historical document, not as a tutorial. Although it has lost little of its didactic value, it describes a language that C compilers today do no longer understand: the C of 1974."

As my C programing skills are somewhat dubious, just butchering

8051's usually. I read most of the article, and I'm still trying to understand the comment

"it describes a language that C compilers today do no longer understand: the C of 1974."

Most of the tutorial seems to make sense too me, what am I missing?

(Not a homework question, just trying to improve my skills)

martin

Reply to
martin griffith
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Main differences that I can think of:

(1) no 'void' in those days.

(2) function declaration is now rather different

(3) Initializer syntax is different ("int x = 1;" rather than "int x 1;")

(4) =operator replaced by operator= ("x += y;" rather then "x =+ y;")

(5) I think short and long modifiers weren't there at the time either; you got 'int' and 'int' was the size of a machine word.

(6) I'm not sure C had unions back in those days, which made certain types of systems programming task harder. (Exotica like bitfields were certainly not there, too).

pete

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Reply to
Pete Fenelon

Thanks, Pete

very helpful

martin

Reply to
martin griffith

(clarifying context restored)

... snip ...

(7) structs could not be passed or returned by value.

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Reply to
CBFalconer

The horse's mouth is of course Dennis Ritchie, you can find more discussion of early C including documents and source code from the period here:

formatting link

Reply to
toby

I should have pointed out that there are still remnants of this around today. The single struct namespace is why a lot of the system structures have redundant looking prefixes on the field names:

For example:

struct timeval { long tv_sec; /* seconds */ long tv_usec; /* microseconds */ }; Then in user code: struct timeval tv;

tv.tv_sec = 1; tv.tv_usec = 0; Why the tv_ on the front of the field names? This seems cleaner:

tv.sec = 1; tv.usec = 0;

But, that would have caused problems if some other structure definition used "sec" or "usec" as field names. So you put a prefix on all structure field names to try to avoid collisions.

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Reply to
Grant Edwards

Thanks. I came to the C party a little later ('86), and started working with pretty much the "K&R first edition" version of the language - so I was working backwards from what I remember of dmr's writings and the examples in that tutorial!

pete

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Reply to
Pete Fenelon

But in K&R, passing, returning and assigning structures wasn't allowed, this was new in K&R2 ('88).

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Stef

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