c++c

How does call by value and call by reference work in C?

In a C program, how does function call by value work, and how does call by reference work, and how do you return a value?

Solution

  • Call by value

    void foo(int c){
    c=5; //5 is assigned to a copy of c
}

    Call it like this:

    int c=4;
foo(c);
//c is still 4 here.

    Call by reference: pass a pointer. References exist in c++

    void foo(int* c){
    *c=5; //5 is assigned to  c
}

    Call it like this:

    int c=0;
foo(&c);
//c is 5 here.

    Return value

    int foo(){
    int c=4;
     return c;//A copy of C is returned
}

    Return through arguments

       int foo(int* errcode){

       *errcode = OK;

        return some_calculation
   }