Thread: Allow them to enter numbers only

Please help me
I want users to enter numbers only

Code:

#include <stdio.h>

int main () {
	float	num;

	printf	("Please Enter Number You want Square of: ");
	scanf	("%f", &num);	
	>>>Something here it tells users to enter numbers only if they enter alphabets then it should not work<<<<
	printf  ("%0.2f squared is equal to %0.2f\n", num, num * num);
        
	return 0;
}

it does work
lets say if it ask user to enter number, and if user enters K
than my program should tell them to enter numbers only

you can check the return value of scanf

Code:

double a;
if (scanf("%lf", &a) != 1) {
//the user didn't enter a number
} else {
...
}

But it will work if the user enters a number followed by something else. Eg, "10.5 asdf"

Depends on what you are trying to do, that can be good or bad.