C :: Converting To Lowercase And Counting Words

I am writing a program when the beginning it you have to pick which step to preform out of a few steps. Once you choose the step. The user is asked to input what is asked and it should preform it. I have completed most of my steps but the one step giving me a hard time is converting a user inputed sentence into all lowercase letters, and then count the words of it. My program starts out like this if you pick this step Code: else

if (choice == 3) {
/* Gather user's input */
printf("
You have chosen to convert a sentence to all lowercase letters and count the words
"
"Enter the sentence: ");
gets ( sentence );

Call the function to convert the whole sentence to lowercase and count the number of words */

lowercase_string ( &sentence);
countSentence ( &sentence);
} /* End if statement */

this is the easy part in which I presume I did correctly, but now this is where I am getting the problems:

/* Prompts user to enter a sentence and convert it to lowercase and count the number of words */

void
countSentence (char *sentence)
void
lowercase_string (char*)
{
[code]....

I want to output the original sentence, then the sentence with all lower case letters, then at last output the number of words in the sentence. I declared all my variables up top, and I am wondering where my mistake is. When trying to compile it, I only get syntax errors which I don't understand.