Stop a for loop when user is finished entering input in c

Question

First of all, thank you for the assist!

I\'m new to the C language (and programming in general) and I\'m trying to write a program wherein the user inputs data point

Answer 1

For your task the loop of gathering input should control not only keyword, but also number if inputs. I suggest to do this as follows:

#include 
#include 
#define NUM_OF_DATA 1048

int main(void) 
{
    printf("\n Welcome! \n\n Please enter each data point. Enter 'done' when finished.\n\n");
    double data[NUM_OF_DATA];
    int i; // counter of entered numbers
    char str[5] = { 0 }; // string to read 'done' or other word from input
    for (i = 0; i < NUM_OF_DATA; i++) // the first index of data in array is 0 (the last NUM_OF_DATA-1)
    {
        printf("Data[%i]: ", i);
        if (1 == scanf("%lf", &data[i])) // if number was successfully read
            continue; // go to next iteration
        // if some problem was with reading a loat number
        // read the string
        scanf("%4s", str); // read not more than 4 characters from input
        if ( strcmp(str, "done") == 0) 
        {
            break; // stop input if 'done' was entered
        }
        // clean input buffer before next input
        while (getchar() != '\n');
        // correct counter in case of wrong input
        i--;
    }
    // output the number of correct inputs
    printf("%d numbers were entered.\n", i);
    // do something with data
    // taking in account, that i is not index of the last element, 
    // but the number of elements (indexes are 0 ... i-1)
    // ...
    return 0;
}

This for loop stops in two cases:

1) when data array is full,

2) when 'done' without quotes entered.

Additional feature is skipping of incorrect input (try how it works).