Source for week 3 content, "reading user input"

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#include <string.h> 
#include <stdio.h>
#include <ctype.h>

int getEmail(char * userEmail);
int getFirstName(char * firstName);
int getLastName(char * lastName);
int getPhoneNumber(char * userPhone);

void main()
{
	char userEmail[80];
	char firstName[80];
	char lastName[80];
	char userPhone[80];
	int nameValid;

	do {
		nameValid = getFirstName(firstName);
		if (nameValid == 1) {
			printf("You entered: %s, a good name\n",firstName);
		}
		else {
			printf("You entered an invalid name, try again\n");
		}
	}
	while (nameValid == 0);
}

int getFirstName(char * charArray)
{
	int entryValid = 1;  // presume entry is valid until we disprove it
	int entryLength,i;

	printf("Enter the first name: ");
	gets(charArray);
	printf("You entered: %s\n",charArray);
	// strlen gives the length of an array of characters
	entryLength = strlen(charArray);   // "John" strlen = 4

	// if user just pressed 'enter', this is not valid
	if (entryLength == 0) {
		return 0;
	}

	// to get here, something must have been entered
	// look at each character individually
	entryValid = 1;
	for (i = 0; i < entryLength; i++) {        // "John" i = 0,1,2,3
		// if a space is in the name, invalidate it
		if (charArray[i] == ' ') {
			entryValid = 0;
		}
		// check if entry is a character
		// if (!x) is the same as if (x == 0)
		if (!isalpha(charArray[i])) {  // !0  is equal to 1
			entryValid = 0;
		}
	}

	return entryValid;

}