C :

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

int main(int argc, char *argv[])
{
  char c;
  int  q=0,e=0,r=0,w=0;
   while((c=getchar())!='\n')
   {
     if((c>='a'&&c<='z')||(c>='A'&&c<='Z'))
       q++;
     else if(c==' ')
        w++;
     else if(c>='0'&&c<='9')
       e++;
       else r++;     
   }
   printf("%d %d %d %d",q,e,w,r);

  return 0;
}

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;
}