C :

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <ctype.h>

int main()
{
	char a[81];
	gets(a);
	int i=0,j=0,k=0,l=0,n;
	for (n=0;a[n]!='\0';n++)
	{
		if (isalpha(a[n]))
			i++;
		else 
			if (a[n]==' ')
			j++;
		else 
			if (isdigit(a[n]))
			k++;
		else
			l++;
	}
	printf ("%d\n%d\n%d\n%d\n",i,j,k,l);
	return 0;
}

C++ :

#include<iostream>
#include<string>
#include<cctype>
using namespace std;
int main()
{
	string s;
	getline(cin,s);
	int len=s.size();
	int letter=0,space=0,digit=0,other=0;
	for (int i=0; i<len; i++)
		if (isalpha(s[i])) letter++;
		else if (s[i]==' ') space++;
		else if (isdigit(s[i])) digit++;
		else other++;
	cout<<letter<<endl<<space<<endl
		<<digit<<endl<<other<<endl;
	return 0;
}