how to make functions?

I need to write a program that calculates the area and perimeters of geometric shapes my question is how do i make it into different functions and in a loop until the user exits the program? if the user enters a none interger or float how should i prompt an error message?
thank you for you time
clear

#include <stdio.h>

void main (){

int chose = 0;
int rwidth = 0;
int rheight = 0;
int rarea = 0;
int rperi = 0;
int swidth = 0;
int sheight = 0;
int sarea = 0;
int speri = 0;
int radius = 0;
int carea = 0;
int cperi = 0;
float pi =3.14;
int base =0;
int rside = 0;
int lside = 0;
int tarea = 0;
int tperi =0;

printf("Please choose 1-5 to calculate\n");
printf("the area and perimeter/circumference\n");
printf("of the various geometric shapes.\n");

printf("1. Rectangle\n");
printf("2. Square\n");
printf("3. Circle\n");
printf("4. Triangle\n");
printf("5. Exit (or EOF, Control+Z)\n");

scanf("%d", &chose);

if (chose == 1){
printf("Please enter the width\n");
scanf("%d", &rwidth);
printf("Please enter the height\n");
scanf("%d",&rheight);

rarea = rwidth * rheight;
rperi = (rwidth * rheight) * 2;

printf("The area of the rectangle is %d\n", rarea);
printf("The perimeter of the rectangle is %d\n", rperi);
}
else if (chose == 2){
printf("Please enter the width\n");
scanf("%d", &swidth);
printf("Please enter the height\n");
scanf("%d",&sheight);

sarea = swidth * sheight;
speri = (swidth * sheight);

printf("The area of the square is %d\n", sarea);
printf("The perimeter of the square is %d\n", speri);
}
else if (chose == 3){
printf("Please enter the radius\n");
scanf("%d", &radius);

carea = pi * radius * radius;
cperi = 2 * pi * radius;

printf("The area of the cirlce is %d\n", carea);
printf("The circumference of the circle is %d\n", cperi);
}
else if (chose == 4){

printf("Please enter the base\n");
scanf("%d",&base);
printf("Pleare enter the left side\n");
scanf("%d", &lside);
printf("Please enter the right side\n");
scanf("%d",&rside);

tperi = base + lside + rside;
tarea = (base * lside) / 2;

printf("The area of the triangle is %d\n", tarea);
printf("The perimeter of the triangle is %d\n", tperi);
}
else if (chose == 5) {

EOF;



}


}

1) Don't use void main(). Use int main().
2) Use code tags (information on the top of every board).
3) EOF; ?? What's this?
4) Instead of that big if, it's better style to use a switch in this case.
5) Look up scanf() in your documentation or on google. Here's a hint (correct me if I'm wrong, I rarely do C):

Code:

if (scanf("%d", num) != 1)
   printf("Invalid input!\n");

speedy 5 your suggestion of use the switch statement was great. thank you
i hadn't thought about it because it hasn't been tought in my class yet.
as for EOF it means end of file and exits the program.
now i got mostly everything down i still have one problem
im suppose to prompt an error message when the user doesnt give a interger when asking for the height, width, side ....etc...
what should i use?
and when i enter things other than intergers the program would just keep looping forever.
one sample output i need is when the use enters triangle and gets an error message and is prompt again
enter again. what do i need for it statement do i need for it to do that and stop looping?
thanks a million
clear

Code:

#include <stdio.h>
#define PI 3.14

void main (){
	
	int chose = 0;
	int rwidth = 0;
	int rheight = 0;
	int rarea = 0;
	int rperi = 0;
	int side = 0;
	int sarea = 0;
	int speri = 0;
	int radius = 0;
	double carea = 0;
	double cperi = 0;
	int base =0;
	int rside = 0;
	int lside = 0;
	int tarea = 0;
	int tperi =0;
	int theight = 0;
	

	printf("Please choose 1-5 to calculate\n");
	printf("the area and perimeter/circumference\n"); 
	printf("of the various geometric shapes.\n");
	do {
	printf("1. Rectangle\n");
	printf("2. Square\n");
	printf("3. Circle\n");
	printf("4. Triangle\n");
	printf("5. Exit (or EOF, Control+Z)\n");

	printf("Enter a value between 1 and 5: ");

		scanf("%d", &chose);

		switch (chose)
		{
		case (1) :	printf("Please enter the width: ");
					scanf("%d", &rwidth);
					printf("Please enter the height: ");
					scanf("%d",&rheight);
		
					rarea = rwidth * rheight;
					rperi = 2 * (rwidth * rheight);
	
					printf("The area of the rectangle is %d.\n", rarea);
					printf("The perimeter of the rectangle is %d.\n", rperi);
					break;
		case (2) :  printf("Please enter the side: ");
					scanf("%d", &side);
						
					sarea = side * 4;
					speri = (side * side);
			
					printf("The area of the square is %d.\n", sarea);
					printf("The perimeter of the square is %d.\n", speri);
					break;
		case (3) :  printf("Please enter the radius: ");
					scanf("%d", &radius);
				
					carea = PI * radius * radius;
					cperi = 2 * PI * radius;

					printf("The area of the cirlce is %.2f.\n", carea);
					printf("The circumference of the circle is %.2f.\n", cperi);
					break;
		case (4) :	printf("Please enter the base: ");
					scanf("%d",&base);
					printf("Pleare enter the left side: ");
					scanf("%d", &lside);
					printf("Please enter the right side: ");
					scanf("%d",&rside);
					printf("Please enter the height: ");
					scanf("%d", &theight);

					tperi = base + lside + rside;
					tarea = (base * theight) / 2;

					printf("The area of the triangle is %d.\n", tarea);
					printf("The perimeter of the triangle is %d.\n", tperi);
					break;
		case (5) : EOF;
			break;

		default :	printf("Invalid choice entered.\n");
					printf("Please enter a value between 1 and 5\n");
					break;
					}
		}
		while (chose != 5);

}

Originally posted by Speedy5
1) Don't use void main(). Use int main().
2) Use code tags (information on the top of every board).
3) EOF; ?? What's this?
4) Instead of that big if, it's better style to use a switch in this case.
5) Look up scanf() in your documentation or on google. Here's a hint (correct me if I'm wrong, I rarely do C):

Code:

if (scanf("%d", num) != 1)
   printf("Invalid input!\n");

About your scanf you're wrong, you forgot '&'.

clear: Post with code tags please. You can use the "edit" button to amend your previous posts to make your code readable.

>>as for EOF it means end of file and exits the program.

Not true, EOF is a Symbolic Integer Constant used to compare things to, not exit the program. If you wanted to do that you will want to use exit(0); with the stdlib.h header file. EOF will do nothing in this state. Its almost like putting -1; in the middle of your code. It just does nothing.

--edit--

What do you want the program to do if the user does enter some odd character instead of 1-5. Ask for another input like if you entered 7?