C :

#include<stdio.h>
#include<string.h>
int main()
{
	char s[100],*p=s;
	int letter,spaces,number,other;
	gets(s);
	while(*p!='\0')
	{
		if((*p>='a'&&*p<='z')||(*p>='A'&&*p<='Z'))
			letter++;
		else if(*p>='0'&&*p<='9')
			number++;
		else if(*p==' ')
			spaces++;
		else
			other++;
		p++;
	}
	printf("%d %d %d %d\n",letter,number,spaces,other);
}

C++ :

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
	char c;
	int letter=0,digit=0,space=0,other=0;
	while ((c=getchar()) != '\n')
		if (isalpha(c)) letter++;
		else if (isalnum(c)) digit++;
		else if (c==' ') space++;
		else other++;
	cout<<letter<<" "<<digit<<" "<<space<<" "<<other<<endl;
	return 0;
}