const int size=80;
char str[size];
int index=0;
char ch=0,lastChar=0;
printf("enter your string(80 chars)\n");
for(int i=0;i<(size-1);i++)/*room for our null byte*/
{
    ch=getchar();
    if(ch == EOF || ch == '\n')
        break;
    if(ch == ' ' && lastChar== ' ')
        continue;
    lastChar = ch;
    str[index] = ch;
    index++;
}
/*fix null byte*/
str[index] = '\0';
printf("%s\n",str);