happpy_2[1]_% cat kadai8-3.c
#include <stdio.h>

main()
{
    char s[10000];
    int n;
    int i;
  
    printf("Enter a sentence.\n");
    gets(s);

    n=0;
    i=0;

    while( s[i] != 0 ){
        if((s[i]>='a' && s[i]<='z') || (s[i]>='A' && s[i]<='Z')){
             if( i==0 || (!(s[i-1]>='a' && s[i-1]<='z') || (s[i-1]>='A' && s[i-1]<='Z'))){
                  n = n + 1;
             }
        }
        i = i + 1;
    }
    printf("String=\"%s\"\n", s ); 
    printf("Word count=%d\n", n ); 
}

happpy_2[2]_% gcc -o kadai8-3 kadai8-3.c -lm
happpy_2[3]_% kadai8-3
Enter a sentence.
There are three things to bear in mind.
String="There are three things to bear in mind."
Word count=8