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I have an SD card which I filled with 15 mp3 tracks and a text file that has 15 words and 15 tracks names. My question is regarding initializing the following

char* words[ ]
char* tracks [ ]

When I initialize them as [100] and [100], the listing of the dB doesn't work as I currently only have 15 tracks and words. I want code to have the ability to place 999.

So my question is: can I make both them variable arrays and how?

I tried leaving between the brackets empty and several other methods but they didn't work. So I wondering if anyone here have any other suggestions.

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Use dynamic memory allocations, malloc and then realloc? – Alok Save Dec 29 '13 at 15:44
    
I tried using malloc but it didn't work, however will try to use realloc, thanks for your fast reply :D – user3133400 Dec 29 '13 at 15:50
    
Note char*words[] is an array of pointers! You will need buffer for string data also char[][]. As this is all dynamic, you better not use static arrays, but use some new keywords. – LS_dev Dec 30 '13 at 10:31
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Arduino code is compiled as C++; you can use the new char[size] and delete[] operators.

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I tried what still i didnt get anything but when i tried using: //words = (char** )calloc(track_size++,sizeof(char*)); //tracks = (char** )calloc(track_size++,sizeof(char*)); with delete []; it only outputs the last word and last track, i dont understand why?? – user3133400 Dec 29 '13 at 20:12
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Arduino version of C/C++ has a great feature - VLA (variable length array, from C99) So, just use:

void process(int n)
{
    // Set up a buffer of n characters
    char b[n];
    // do the work
}

See: http://www.drdobbs.com/the-new-cwhy-variable-length-arrays/184401444

You need array of arrays? No problem (I hope). Pseudocode:

char* words[N]; // N - words
char word1[M] // M - word length
char word2[O] // O - second word length

words[0] = word1;
words[1] = word2;

Many answers suggest to use dynamic memory allocation - it works, but main drawback of such method - memory fragmentation. But remember - dynamic memory allocation is only method to return arrays from functions!

P.S. I can't verify code with compiler at the moment - please give me feedback if it doesn't work.

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