What does char[n][100] mean?

Question

My professor gave me a C file and I can't really understand it well. It's a program that reads from a text file.

#include <stdio.h>
main(){
    int n,m;
    char start[30],end[30];
    FILE *a;
    a=fopen("test.txt","r");
    fscanf(a,"%s",&start);
    fscanf(a,"%s",&end);
    fscanf(a,"%d",&m);
    fscanf(a,"%d",&n);
    printf("\n%s\n%s\n%d\n%d",start,end,m,n);
    char word[n][30];
    int i=0;
    while(!feof(a)){
        fscanf(a,"%s",&word[i]);
        i++;

    }

    for(i=0;i<n;i++)
        printf("\n%s",word[i]);
    fclose (a);

}

here's the text file:

blah alooa
7 4
hey
boom
stackoverflow
testing

So, I'm wondering what does this char word[n][30] mean? why does it have [n]?

On an unrelated note, please read [Why is “while (!feof(file))” always wrong?](https://stackoverflow.com/questions/5431941/why-is-while-feoffile-always-wrong) You might want to forward the link to your professor. — Some programmer dude, Mar 01 '19 at 07:56
Lundin, I don't have a class for the next 2 weeks, that's why. — MareGraphics MaRe, Mar 01 '19 at 08:01
If your C book doesn't cover what a VLA (variable length array) is, it is time you got a book written in the current millennium (and written to take into account the changes made by C99, and preferably C11 too, though the changes in C11 are small by comparison with those in C99). — Jonathan Leffler, Mar 01 '19 at 08:38
@JonathanLeffler Can you please recommend any good book ? I know many, but I want your recommendation. — Mazhar, Mar 01 '19 at 09:59
See [The Definitive C Book Guide and List](https://stackoverflow.com/questions/562303/the-definitive-c-book-guide-and-list). I think K N King "C Programming: A Modern Approach (2nd Edn)" is a good choice. It doesn't cover C11 per se, but does cover C99. — Jonathan Leffler, Mar 01 '19 at 15:04

Mazhar · Accepted Answer · 2019-03-01T08:06:44.833

2

So, I'm wondering what does this char word[n][30] mean?

Technically, it is a 2 dimensional VLA of characters. It is used in this program to store "n" words, where each word can be of max 30 characters length.

why does it have [n]?

It's a variable used to store the number of words in the file.

Looking at your program, probably, you have to enter 8 as the value of n.

edited Mar 01 '19 at 08:06

answered Mar 01 '19 at 07:59

Mazhar

575
5
20

score -1 · Answer 2 · answered Mar 01 '19 at 09:04

-1

Well n is the number if word you have and it is readed from the file. It’s like you have some parameters stored within your file in the first lines

answered Mar 01 '19 at 09:04

Amie Joni

45
1
5

What does char[n][100] mean?

2 Answers2