C language: count the number of words in a paragraph

The big premise ： Words are separated by spaces
Little premise ： What I write is all lowercase .

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include<string.h>
#define size 50
int fun(char s[])
{
    
	int i = 0, num = 0;
	while (i < size)
	{
    
		if (s[i] != '\0')
		{
    
			if ((65 <= s[i] && s[i] <= 90) || (97 <= s[i] && s[i] <= 122))
			{
    
				while ((65 <= s[i] && s[i] <= 90) || (97 <= s[i] && s[i] <= 122))
					i++;
				num += 1;
				while (s[i] == ' ')
					i++;
			}
		}
		if (s[i] == '\0')
			break;
		i++;
	}
	return num;
}
int main()
{
    
	char s1[size];
	gets(s1);
	printf(" Altogether %d Word ", fun(s1));
	return 0;
}

**if (s[i] != ‘\0’)** To prevent an array from being accessed beyond its bounds .

**if ((65 <= s[i] && s[i] <= 90) || (97 <= s[i] && s[i] <= 122))** To skip other types of character interference , Let the traversal of other characters pass there i To skip .

This is to traverse the letters .

This is to traverse spaces .