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referring to ANSI C book by K and R
"With a little care it is easy to write portable programs, The standard makes portability issues explicit"
I expects, he hints me, that the C language <without the standard library> , is portable and, if I dont use the std. library, my program is guarenteed to run over any system.
but how can I write a program without the std. library, when even writing a simple Hello World program requires stdio.h library?
What exactly is the part that hints that? It seems to me that what you quoted means that it is possible to write portable C prograns that use the standard library (since that is part of the standard), as long as you are careful not to use it in a nonportable way (e.g., relying on system() calls).Quote:
I expects, he hints me, that the C language <without the standard library> , is portable and, if I dont use the std. library, my program is guarenteed to run over any system.
If your program only uses the standard library, then it will be portable.
> but how can I write a program without the std. library
This normally happens when you start writing programs for free-standing implementations (also know as an embedded system). Say for example you have a micro processor attached to a particular kind of LCD display.
Your program writes "hello world" to the LCD, via some LCD library (possibly written by you). If in the future you want to use another kind of LCD display, then you might need another library (or you might need to write it yourself).
It's more a case of you don't need a std library in order to be able to write code for the machine in question. However, all free-standing code is inherently non-portable.