As part of the crossword grid packing utility, the first stage is building the list of words in a structure in RAM. To keep thing simple I’m going to use an array of char * pointers. The array is limited to a maximum 20 words. If any more are read then they will be discarded.

Just to prove that it worked, I wrote this in Visual Studio and ran it in the debugger. You can see elements 0-9 in the screenshot with the source code in the background.

This is the listing of the program. Note, it doesn’t have a function to free up the memory dynamically allocated for each of the words.

You might wonder about these lines (25 and 26).

	if (line[len-1] == '\n')
		line[--len] = '\0';

This is needed because when you use fgets to read a line of text it includes a line feed at the end. So the first line in the file Engine is actually 7 characters long with a terminating \n. The malloc on line 27 allocated enough RAM for len + 1 to allow for the terminating 0 at the end of each string. In line 33, if you are on Linux replace strcpy_s with strncpy. Both are safe versions of strcpy. Here’s the full listing.

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

#define MAXWORDS 20
#define MAXWORDLENGTH 32

typedef char* pWord;
pWord allwords[MAXWORDS];

int ReadWords(char * filename) {
	memset(allwords, 0, sizeof(allwords)); // clear it
	char line[MAXWORDLENGTH*2]; // double max size just in case
	FILE* fwords;
	int errnum = fopen_s(&fwords,filename, "rt");
	if (!fwords) {
		printf("Missing word file %s", filename);
	}
	int wordIndex = 0;
	while (fgets(line, MAXWORDLENGTH, fwords)) {
		int len = strlen(line);
		if (!len)
			break;
		if (line[len-1] == '\n')
			line[--len] = '\0';
		pWord pNewWord = (pWord)malloc(len + 1);    // line 27
		if (!pNewWord) {
			printf("Error allocating memory");
			break;
		}
		if (wordIndex < MAXWORDS) { // can add to list
			strcpy_s(pNewWord, len+1, line);  // line 33
			allwords[wordIndex++] = pNewWord;
		}
	}
	fclose(fwords);
	return wordIndex; // = Count of words
}

int main() {
	int numWordsread = ReadWords("words.txt");
}