Scanning Values Until Getting a Significant Character in C - c

Question

For my homework, I am trying to code a calculator which can also calculate average of taken numbers. I don't want to ask for number of numbers because our teacher don't want it in that way. So I thought of scanning values until the user presses "p". But as you would guess, the numbers are float and "p" is a character. What I want to do is assigning the value scanned to both of them if it is possible. I tried different ways, played with the codes but it isn't working properly. So I am seeking your advice.
It prints a value when p is inputted as like 3rd, 5th, 7th (oddth) number (sometimes right, sometimes wrong but I can fix it if I figure this out). But it doesn't print a value in other occasions and expects infinite inputs from the user.
This is the code I have written for this. scanf("%f %c", &number1, &pause); command is where I want to know about, actually.
#include<stdio.h>
float number1, number2, i, result;
char pause;
int main() {
scanf("%f", &number1);
i = 0;
while (pause != 'p') {
number2 = number1 + number2;
scanf("%f %c", &number1, &pause);
i++;
}
result = number2 / (i - 1);
printf("%f", result);
}

Answer 1

Use double not floats if there is no specific reason to do so (like using uC without double FPU).
You do not initialize the variables
Always check the result of the I/O operation.
#include <stdio.h>
int main ()
{
double number1= 0, number2 = 0, i = 0, result = 0;
char pause = 0;
char line[128];
while (pause != 'p')
{
if(fgets(line, sizeof(line), stdin))
{
if(sscanf(line, "%lf %c",&number1, &pause) != 2)
{
printf("Wrong input - try again\n");
pause = 0;
continue;
}
number2 = number1 + number2;
i++;
}
else
{
// do something with I/O error
}
}
result = number2 / (i-1);
printf("%lf",result);
}
You can play with it yourself : https://onlinegdb.com/Hy3y94-3r

Answer 2

I noticed 3 problems with your code.
First I would advise you to use meaningful variables names. number1, number2, etc. and the i which represents the number of inputs given can be an int instead of a float.
Secondly, you lack of printing to the user what's going on in your program; it's better to have messages like "enter your number, do you wanna stop? the result is...etc".
Lastly, having two inputs in one line of code can make it hard to debug, knowing that reading strings and characters in C is already hard for beginners. For example, %c does not skip whitespace before converting a character and can get newline character from the previous data entry.
Here is my fix: I changed some variables' names, printed some messages and read the two inputs in two different lines with adding scanf(" %c") with the space to avoid that problem.
#include<stdio.h>
float sum, temp, result;
int nb;
char pause;
int main () {
pause='a';
while (pause != 'p'){
printf("Enter your number: ");
scanf("%f",&temp);
sum+=temp;
nb++;
printf("type 'p' if you want to stop: ");
scanf(" %c",&pause);
}
result = sum / nb;
printf("the average is : %f",result);
}
I tested it, should work fine
Edit: after explaining that you don't want to ask the user each time, here is how the code should work (the case that the user don't input a float is not treated, and just take it as zero
#include<stdio.h>
#include<string.h>
#include <stdlib.h>
float sum, temp, result;
int nb;
char input[50];
int main () {
sum=0;
nb=0;
printf("Enter your numbers, then type 'p' to stop\n");
do{
printf("Enter your next number: ");
scanf("%s", input);
if(strcmp(input,"p")!=0)
{
float temp= atof(input);
sum+=temp;
nb++;
}
}while(strcmp(input,"p")!=0);
if(nb!=0)
result = sum / nb;
printf("\nThe average is : %f",result);
}