Below is an example of passing a struct, a statically declared array, and two ints to a function. All arguments are passed by value to the function. However, becasue the value of the array name argument is the base address of the array argument, the parameter refers to the same array buckets as the argument. Thus, the function can modify the bucket values in the passed array, whereas it cannot modify any values of the struct or int arguments.

After the example code is a drawing of the stack right before the return from crazy_function.

The program:

  #include <stdio.h>
  #include <string.h>

  struct personT {
  	char name[32];
  	int  age;
  };

  // a function prototype:
  void crazy_function(int i_val, struct personT per, int a[], int n);

  //
  // main function:
  //
  int main() {

  	struct personT person;
  	int x, i;
  	int arr[5];

  	for(i=0; i < 5; i++) {
  	   arr[i] = i;
  	}
  	for(i=0; i < 5; i++) {
  	   printf("arr[%d] = %d\n", i, arr[i]);  // bucket values: 0 1 2 3 4 
  	}
  	x = 10;
  	strcpy(person.name, "Tia");
  	person.age = 21;
  
  	crazy_function(x, person, arr, 5);
  
  	for(i=0; i < 5; i++) {
  	   printf("arr[%d] = %d\n", i, arr[i], 5);   // bucket values: 0 1 4 9 16
  	}
  	printf("x = %d age = %d name = %s\n", x, person.age, person.name);  // values:  10 21 Tia
  }
  //
  // crazy function definition:
  //
  void crazy_function(int i_val, struct personT per, int a[], int n) {
  	int i;
  
  	for(i=0; i < n; i++) {
  	   a[i] = a[i]*a[i];
  	}
  	strcpy(per.name, "Ace");
  	per.age = 18;
  	i_val = 100;
  
  	//**** THE STACK IS DRAWN RIGHT BEFORE THE return STATMENT IS EXECUTED
  	return;
  }

The stack right before crazy_function returns:

                                       STACK

                |=====================================================|   
crazy_function: |         -------                                     |
                |       i |  5  |                                     |
                |         -------                                     | 
                |         -------                                     |
                |   i_val | 100 |                                     |
                |         -------                                     |
                |        ------------------------------------------   |
                |    per | name : |'A'| 'c'| 'e' |'\0'|  ...  |   |   |
                |        ------------------------------------------   |
                |        |  age : |            18                 |   |
                |        ------------------------------------------   |
                |        ---------                                    |
                |      a |   *-- |--------------------------------------------
                |        ---------                                    |      |
                |         -------                                     |      |
                |      n  |  5  |                                     |      |
                |         -------                                     |      |
                |=====================================================|      |
      main:     |                                                     |      |
                |                                                     |      | 
                |         --------------------------------------------------- 
                |         |                                           | 
                |        \/                                           |
                |        -----------------------                      |
                |    arr | 0 | 1 |  4 | 9 | 16 |                      |
                |        -----------------------                      |
                |         -------                                     |
                |       x | 10  |                                     |
                |         -------                                     |
                |         -------                                     |
                |       i |  5  |                                     |
                |         -------                                     | 
                |        ------------------------------------------   |
                | person | name : |'T'| 'i'| 'a' |'\0'|  ...  |   |   |
                |        ------------------------------------------   |
                |        |  age : |            21                 |   |
                |        ------------------------------------------   |
                |                                                     |
                |=====================================================|