What are the important notions in C that you did not learn from your teachers? [closed]

Answer 1

My teachers spent so much time teaching us that pointers are scary little goobers that can cause lots of problems if not used correctly, that they never bothered to show us how powerful they can really be.

For example, the concept of pointer arithmetic was foreign to me until I had already been using C++ for several years:

Examples:

• c[0] is equivalent to *c
• c[1] is equivalent to *(c + 1)
• Loop iteration: for(char* c = str; *c != '\0'; c++)
• and so on...

Rather than making students afraid to use pointers, teach them how to use them appropriately.

EDIT: As brought to my attention by a comment I just read on a different answer, I think there is also some value in discussing the subtle differences between pointers and arrays (and how to put the two together to facilitate some pretty complex structures), as well as how to properly use the const keyword with respect to pointer declarations.

Answer 2

Tools are important, so I'd recommend to at least mention something about

• Makefiles and how the build process works
• gdb
• lint
• the usefulness of compiler warnings

Concerning C, I think it's important to stress that the programmer should know what "undefined behaviour" really means, i.e. to know that there could be a future problem even if it seems to work with the current compiler/platform combination.

Edit: I forgot: teach them how to search and ask proper questions on SO!

Answer 3

When I had to use C as part of a larger project in school it was the ability to use gdb properly (i.e. at all) that ended up predicting who would finish their project and who would not. Yeah if things get crazy and you have tons of pointer and memory related bugs gdb will show weird information but even knowing that can point people in the right direction.

Also reminding them that C isn't C++, Java, C#, etc. is a good idea. This comes up most frequently when you see someone treating a char* like a string in C++.

Answer 4

I don't think you should be teaching tools. That should be left to Java teachers. They are useful and widely used but have nothing to do with C. A debugger is as much as they should hope to get access to. Many times all you get is printf and/or a blinking LED.

Teach them pointers but teach them well, telling them that they are an integer variable representing a position in memory(in most courses they also have some training in assembly even if it is for some imaginary machine so they should be able to understand that) and not an asterisk prefixed variable that somehow points to something and that sometimes becomes an array(C is not Java). Teach them that C arrays are just pointer + index.

Have them write programs that will overflow and segfault for sure and after that, make sure they understand why it happened.

The standard library is also C, have them use it and have their programs die painfully in your private tests because of having used gets() and strcpy() or double-freed something.

Force them to deal with variables of different type, endianness(Your tests could run in a different arch), float to int conversion. Make them use masks and bitwise operators.

i.e. teach them C.

What I got instead was some batch processing in C that could as well have been done in GW-BASIC.

Answer 5

Object orientation:

struct Class {
    size_t size;
    void * (* ctor) (void * self, va_list * app); // constructor method
    void * (* dtor) (void * self);                // destructor method
    void (* draw) (const void * self);            // draw method
};

(Code source)

Answer 6

1. Check the boundaries

2. Check the boundaries,

   and of course,

3. Check the boundaries.

And if you forgot one of these rules, use Valgrind. This applies to arrays, strings, and pointers, but it's really very easy to forget about what you're really doing when doing allocations and memory aritmethics.