bad_square.c

#include <stdio.h>
#include <stdlib.h>

long long badsquare(long long n);

int main(int argc, char **argv)
{	
	if(argc < 2)
	{
		printf("Please enter the number to square\n");
		return 1;
	}
	
	printf("Not so regular square: %lld\n",badsquare(strtoll(argv[1],NULL,0)));
	return 0;
}

long long badsquare(long long n)
{
	long long k = 0;
	for(;;)
	{
		if(k == n*n)	
		{
			return k;
		}
		k++;
	}
}

good_square.c

#include <stdio.h>
#include <stdlib.h>

long long square(long long n);

int main(int argc, char **argv)
{	
	if(argc < 2)
	{
		printf("Please enter the number to square\n");
		return 1;
	}
	
	printf("Regular square: %lld\n",square(strtoll(argv[1],NULL,0)));
	return 0;
}

long long square(long long n)
{
	return n*n;
}