Problem with a basic code

Using Arduino Programming Questions
1

My code i as follows:

float radius;
String msg="What is the radius of your circle? ";
float area;
String msg2="Your circle has an area of: ";
float pi=3.14;

void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
}

void loop() {
// put your main code here, to run repeatedly:
Serial.println(msg);
while (Serial.available()==0);

radius=Serial.parseFloat();
area=piradiusradius;
Serial.print(msg2);
Serial.println(area);

}

//the result i get in my serial monitor is as follows:

What is the radius of your circle?
Your circle has an area of: 12.56
What is the radius of your circle?
Your circle has an area of: 0.00
What is the radius of your circle?

// I entered 2 as my variable and get the proper result. then I get the second entry of "Your circle has an area of: 0.00.

have not figured out why.

2

Change the line ending setting on the serial monitor to "no line ending" or "none" or whatever gives no line-ending character like CR or LF, or both..

Please remember to use code tags when posting code

3

Coding tags? I am very new to this. Thank you so very much for your assistance.

4

No, code tags.

5

Code tags?

6

Yes, that's right.

The things that stop your posted code making no sense.
(Hint: read it back and compare it to your actual code)

7

can you show me which line you are referring to?

I will go back and look at the posting requirements for code.
Thank you so very much. I started this just a few days ago and am now addicted.

8

The line in your original post that doesn't look like the same line in your original code.

9

consider (Arduino sprintf lacks floating pt formating)

String prompt ="What is the radius of your circle? ";

char s0 [80];
char s1 [20];
char s2 [20];

void setup() {
    Serial.begin(9600);
    Serial.println(prompt);
}

void loop() {
    if (! Serial.available())
        return;                     // nothing to do

    int n = Serial.readBytesUntil ('\n', s0, sizeof(s0));
    s0 [n] = 0;                     // replace '\n' with null

    float radius = atof (s0);
    float area   = PI * radius * radius;

    dtostrf (radius, 8, 3, s1);
    dtostrf (area,   8, 3, s2);
    sprintf (s0, " radius %s, area %s", s1, s2);    // reuse s0
    Serial.println (s0);

    Serial.println(prompt);
}
10

There is no need to re-invent PI, it's already defined for you in the core. Here is the source code:

#define PI 3.1415926535897932384626433832795
11

Hi, @krebad
Welcome to the forum.
Please read the post at the start of any forum , entitled "How to use this Forum".

Thanks.. Tom... :grinning: :+1: :coffee: :australia:

12

There's more than one way to do it, by the way. You can click on the button marked </> while you are editing, you can use traditional [code] and [/code] tags, or (my favourite and the most versatile) you can post your code between 2 instances of 3 consecutive backticks, with the optional indication of the language (usually cpp), like so:

```cpp
// Your code goes here
```
13

At least, OP truncated it to 2 decimal places. Once upon a time, the State of Indiana did much worse.

14

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