What do c and h file extensions mean to C

Question

It s all in the title  super-simple I reckon  but it s so hard to search for syntactical things anywhere   These are two library files that I m copying from CS50 net  and I m wondering why they have two different extensions

User · Answer

The  c is the source file and  h is the header file

User · Answer

The  c files are source files which will be compiled  The  h files are used to expose the API of a program to either other part of that program or other program is you are creating a library   For example  the program PizzaDelivery could have 1  c file with the main program  and 1  c file with utility functions  Now  for the main part of the program to be able to use the utility functions  you need to expose the API  via function prototype  into a  h file  this  h file being included by the main  c file

User · Answer

c    C  source code  h   Header file   Usually  the  c files contain the implementation  and  h files contain the  interface  of an implementation

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Of course  there is nothing that says the extension of a header file must be  h and the extension of a C source file must be  c  These are useful conventions   E  Temp gt  type my interface  ifndef MY INTERFACE INCLUDED  define MYBUFFERSIZE 8  define MY INTERFACE INCLUDED  endif  E  Temp gt  type my source  include  lt stdio h gt    include  my interface   int main void        char x MYBUFFERSIZE     0       x 0     a       puts x       return 0     E  Temp gt  gcc -x c my source -o my exe  E  Temp gt  my a

User · Answer

c   c file  where the real action is  in general    h   header file  to be included with a preprocessor  include directive   Contains stuff that is normally deemed to be shared with other parts of your code  like function prototypes   define d stuff  extern declaration for global variables  oh  the horror  and the like   Technically  you could put everything in a single file  A whole C program  million of lines  But we humans tend to organize things  So you create different C files  each one containing particular functions  That s all nice and clean  Then suddenly you realize that a declaration you have into a given C file should exist also in another C file  So you would duplicate them  The best is therefore to extract the declaration and put it into a common file  which is the  h  For example  in the cs50 h you find what are called  forward declarations  of your functions  A forward declaration is a quick way to tell the compiler how a function should be called  e g  what input params  and what it returns  so it can perform proper checking  for example if you call a function with the wrong number of parameters  it will complain    Another example  Suppose you write a  c file containing a function performing regular expression matching  You want your function to accept the regular expression  the string to match  and a parameter that tells if the comparison has to be case insensitive   in the  c you will therefore put   bool matches string regexp  string s  int flags    the code     Now  assume you want to pass the following flags   0  if the search is case sensitive  1  if the search is case insensitive  And you want to keep yourself open to new flags  so you did not put a boolean  playing with numbers is hard  so you define useful names for these flags   define MATCH CASE SENSITIVE 0  define MATCH CASE INSENSITIVE 1   This info goes into the  h  because if any program wants to use these labels  it has no way of knowing them unless you include the info  Of course you can put them in the  c  but then you would have to include the  c code  whole   which is a waste of time and a source of trouble

User · Answer

They re not really library files  They re just source files  Like Stefano said  the  c file is the C source file which actually uses defines the actual source of what it merely outlined in the  h file  the header file  The header file usually outlines all of the function prototypes and structures that will be used in the actual source file  Think of it like a reference appendix  This is evident upon looking at the header file  as you will see    So then when you want to use something that was written in these source files  you  include the header file  which contains the information that the compiler will need to know

[c] What do .c and .h file extensions mean to C?

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