Parameter Passing in C – Pointers, Addresses, Aliases

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  1. Call-by-value

    Passing the value to a function as a parameter. If the function modifies the variable, the actual variable won’t get changed.

    void fun1(int myParam)
{
    myParam = 4;
}

void main()
{
    int myValue = 2;
    fun1(myValue);
    printf("myValue = %d",myValue);
}

    myValue will always be 2.

  2. Call-by-address (pointer)

    void fun1(int *myParam)
{
    *myParam = 4;
}
void main()
{
    int myValue = 2;
    fun1(&myValue);
    printf("myValue = %d",myValue);
}

    Here we are passing the address of myValue to fun1. So the value of myValue will be 4 at the end of main().

  3. Call-by-alias

    There is no alias in C as per my understanding. It should be the C++ reference mechanism.

  4. Global variable / Static variable

    Global and static variables are variables stored in a common places, accessible by the caller and callee functions. So both caller and callee will be able to access and modify them.

    int myValue = 2;
void fun1()
{
    myValue = 4;
}
void main()
{
    myValue = 2
    fun1();
    printf("myValue = %d",myValue);
}

    As you can guess, the value of myValue will be 4 at the end of main().

Hope it helps.

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  2. Passing an array as an argument to a function in C
  3. How do you pass a function as a parameter in C?
  4. Pointers as function arguments in C
  5. Changing address contained by pointer using function
  6. C Programming: malloc() inside another function
  7. Difference between passing array and array pointer into function in C
  8. Function pointers and address of a function
  9. Why do we need to specify the column size when passing a 2D array as a parameter?
  10. Returning Arrays/Pointers from a function
  11. Passing arrays and matrices to functions as pointers and pointers to pointers in C
  12. Changing array inside function in C
  13. How is the result struct of localtime allocated in C?
  14. When is an array name or a function name ‘converted’ into a pointer ? (in C)
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  16. Manipulate multidimensional array in a function
  17. Unspecified number of parameters in C functions – void foo()
  18. Function pointer as a member of a C struct
  19. Pass by reference in C
  20. In a C function declaration, what does “…” as the last parameter do?
  21. What is the function of an asterisk before a function name?
  22. C pointer notation compared to array notation: When passing to function
  23. Function does not change passed pointer C++
  24. Pointers in C: when to use the ampersand and the asterisk?
  25. Post-increment on a dereferenced pointer?
  26. Why do I need to use type** to point to type*?
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  28. Array of size 0 at the end of struct [duplicate]
  29. Avoiding the main (entry point) in a C program
  30. lvalue required as increment operand

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