PASS Week 2/17

REFERENCE MATERIAL


Structure of a Function in C:
The portion of C code that contains the program of a function is the function definition.
The following illustrates it’s form.

/* You would put your block comment here describing what the function does */

type function_name (parameters with types){
	Local declarations
	Local statements including the return statement.
}






Example Code for Pointers:
This code will swap the values of A and B using a function and pointers.

void exchange(int*, int*); //Function prototype

int main(void){
	int a, b;
	exchange(&a,&b); //Function call

	return 0;
}

/* Function definition */
void exchange(int* pa, int* pb)
{
	int c;
	c = *pa;
	*pa = *pb;
	*pb = c;
	return;
}















FLOW OF CONTROL/FUNCTIONS EXAMPLE PROBLEM

Answer the questions in the comments of this code BEFORE running it.
Run it afterward to check your results!



#include <stdio.h>

//What are these two below statements called?
int myFunction1(void);
int myFunction2(int);

// List the chronological order the functions execute in this program (Including main)
int main(void){

	int x = 7;
	int y = 0;

	myFunction1(); //What does this do? What arguments does this take?
	myFunction2(x); //What does this do? What arguments does this take?

	y = myFunction1() + myFunction2(x);     //What does y equal?

	//What is different between the printf function and myFunction1/myFunction2?
	printf("%d\n", y);

	return 0;
}

int myFunction1(void){
	return 5;
}

int myFunction2(int myVar){
	return myVar + 2;
}















Answer the questions in the comments of this code.
Run it afterward to check your results, try changing the statements/values and see what you get!

#include <stdio.h> /* for printf() */

int main(void)
{
	int i;
	int* p = &i;    //What value does variable *p store?

	printf("%p\n", p);   //What will this print? (Remember what the %p formatter does)

	return 0;
}



















Problem #1 Using pointers

Construct a program that prompts the user to enter in two type double values and
store them into two type double variables. Then declare two pointer variables and assign them to point to
the variables declared in the previous step. Now add the two inputs together USING THE
POINTERS to the two variables and assign the result to a new value variable, print it to
screen.













Problem #2 Pass by Reference

Using the program from problem 1, create a function called “AddNbrs()” that takes
three double pointer variables and returns nothing to the caller. Keep the two input
variables and the user prompts and outputs within main. Move the expression that adds the
values into the new function. Then assign the result using the
pointers passed to the function from main.

/*** SKELETON CODE ***/

#include <stdio.h>

void AddNbrs(double*, double*, double*); //Function prototype given

int main()
{

 //START PROGRAMMING HERE

 return 0;
}

//WRITE FUNCTION HERE













Problem #3

Create a program that makes use of pointers to take in two user-supplied values, being the
length of 2 sides of a 4 sided polygon (square or rectangle). Your program should
prompt the user from inside main to enter in the length of two adjacent sides of a 2-
sided polygon. It should then call a single function to compute the area AND perimeter of the
polygon and return those values using pointers to the calling function. The output
should be presented in a meaningful way to the user.














Problem #4

Create a program that prompts the user to enter in a value for number of
seconds using a long data type. Create a function that when given a value
representing seconds will return the number of hours, minutes and seconds
contained in that value of seconds. While the function can take the seconds variable
as input, the three measures should be returned to the calling
function by using pointers.

You may assume that the user will not enter more than 24 hours worth of seconds.











Problem #5:

Write a program that uses a function that receives a pointer to a type double
number and two integer variables and sends back the integer and fraction parts as
integers using pointers up to the hundredth place. In your main
function prompt for the user to input a type double number, then call the
function, then output the parts from main after the function returns them using
pointers. Hint use modulus and division.

So if a user enters in 98.65 , the function should return 98 and 65