C++ Program stopped responding - c++

Question

I have made a program that runs and I am able to enter in three variables, length, external diameter and internal diameter. After I enter in internal diameter the program freezes and a window pops up saying the program has stopped responding. The program's purpose is to calculate area, volume, mass, weight etc. of a cylindrical pipe given a number of variable inputs.
Any help would be appreciated.
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#define PI 3.14159
#define ACC_GRAVITY 9.81 /* metres/sec^2 */
#define FALSE 0
#define TRUE !FALSE
int main(void)
{
/* define the required variables */
float length;
float ext_diam, int_diam;
float ext_rad, int_rad;
float volume;
float weight;
float area;
float mass;
float width;
float flag_1, flag_2, thickness, percent;
double no_sheets;
/* define some constants - could use #define */
const float density_convert = 1.0E3;
const float mm_to_metres = 1.0E-3;
const float density = 8.03; /* grams per cm^3 */
/* prompt and get values */
printf("input the length of pipe in metres: ");
scanf("%f", &length);
do
{
flag_1 = FALSE;
flag_2 = FALSE;
printf("intput the external diameter of the pipe in milimeters: ");
scanf("%f", &ext_diam);
printf("ext_diam: %f\n", ext_diam);
printf("intput the internal diameter of the pipe in milimeters: ");
scanf("%f", int_diam);
printf("int_diam: %f\n", int_diam);
if (ext_diam < int_diam)
{
printf("external diameter must be greater than the internal diameter\n");
flag_1 = TRUE;
}
else
{
percent = thickness / ext_diam * 100.0;
if(percent > 2.5 )
{
/* do calculations - conversions, area of pipe cross-section, volume
** of pipe, mass and weight of pipe */
ext_diam = ext_diam * mm_to_metres;
int_diam = int_diam * mm_to_metres;
ext_rad = ext_diam / 2.0;
int_rad = int_diam / 2.0;
area = (PI * ext_rad * ext_rad) - (PI * int_rad * int_rad);
volume = area * length;
mass = volume * density * density_convert;
weight = mass * ACC_GRAVITY;
}
else
{
printf("Width of pipe too small\n");
flag_2 = TRUE;
}
}
} while(ext_diam > 0.0);
/* output the results */
printf("area of cylinder: %f m^2\n", area);
printf("volume of steel needed: %f m^3\n", volume);
printf("mass of steel needed: %f kg\n", mass);
printf("weight of steel needed: %f newtons\n", weight);
/* compute number of sheets of steel needed - 10m is max length of a
** sheet */
no_sheets = trunc (length / 10.0) + 1;
printf("number of 10m long sheets needed: %d\n", no_sheets);
/* assume width of sheets is based on the average of the internal and
** external diameters */
width = 2.0 * PI * (ext_rad + int_rad) / 2.0;
printf("width of sheets: %f m\n",width);
system("pause");
return 0;
}

Answer 1

There are some issues with your code:
scanf("%f", int_diam);, scanf needs a pointer to the variable, this will work
scanf("%f", &int_diam);
In the line
percent = thickness / ext_diam * 100.0;
thickness is not initialized the first time it is used (did you forget a passage?)
Not sure if the termination when ext_diam is <= 0 is intended.
Finally, there are multiple double-to-float conversions (e.g. area calculus) which might cause loss of data

Answer 2

Change scanf("%f", int_diam); to scanf("%f", &int_diam);
Also, your do while loop seems to go into an infinite loop. Since it depends on the external diameter, either change the loop condition, or ensure that external diameter will reach a value <=0 inside the loop. Your do while loop will only terminate when user enters a non-positive value for ext_diam.
Also, assuming thickness refers to the thickness of the pipe, add this equation before you use this variable thickness=ext_diam-int_diam;, or any other formula you use to calculate the thickness.