Readability checker written with C, according to Scholastic standards.

readability.c

#include <stdio.h>
#include <cs50.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

int letterCounter(char paragraph[], int);
int wordCounter(char paragraph[], int);
int sentenceCounter(char paragraph[], int);

int main(void) {
    int totalLetters, totalWords, totalSentences, length;
    float index, letter100, sentence100;
    string paragraph;

    paragraph = get_string("Enter your text: ");

    length = strlen(paragraph);

    char letterArray[strlen(paragraph)];
    for(int i=0; i<strlen(paragraph); i++) {
        letterArray[i]=paragraph[i];
    }
    totalLetters = letterCounter(letterArray, length);
    totalWords = wordCounter(letterArray, length);
    totalSentences = sentenceCounter(letterArray, length);

    letter100 = ((totalLetters*100)/totalWords);
    sentence100 = ((totalSentences*100)/totalWords);

    index = (0.0588*letter100) - (0.296*sentence100) - 15.8;

    // printf("%f\n", index);

    if (index > (floor(index)+.54f)) {
        index = ceil(index);
    } else {
        index = floor(index);
    }

    // printf("%f\n", index);

    printf("Text: %s\n", paragraph);
    printf("%d letter(s)\n", totalLetters);
    printf("%d word(s)\n", totalWords);
    printf("%d sentence(s)\n", totalSentences);

    if(index < 1) {
        printf("Before Grade 1\n");
        return 0;
    } else if (index >= 16) {
        printf("Grade 16+\n");
        return 0;
    } else {
        printf("Grade %.0f\n", index);
        return 0;
    }

}

int letterCounter(char paragraph[], int length) {
    int count = 0;

    for(int i=0; i<length; i++) {
        paragraph[i] = tolower(paragraph[i]);
        if (paragraph[i] > 96 && paragraph[i] < 123) {
            count += 1;
        }
    }

    return count;
}

int wordCounter(char paragraph[], int length) {
    int count = 0;

    for(int i=0; i<length; i++) {
        paragraph[i] = tolower(paragraph[i]);
        if (paragraph[i] == 32) {
            count += 1;
        }
    }

    return count+1;
}

int sentenceCounter(char paragraph[], int length) {
    int count = 0;

    for(int i=0; i<length; i++) {
        paragraph[i] = tolower(paragraph[i]);
        if (paragraph[i] == 46 || paragraph[i] == 33 || paragraph[i] == 63) {
            count += 1;
        }
    }

    return count;
}