Hello, I am a student who is learning C language. I'm asking you a question regarding the code.

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

#define WIDTH 512
#define HEIGHT 512 // WIDTH, defined as 512 for each HEIGHT
Typeef unsigned char BYTE; // Express unsigned char as BYTE 

int main()
{
    FLE *fp_in = 0, *fp_out = 0; // generate a pointer after substituting the garbage value 0 in fp_in and fp_out.
    BYTE **img_in = 0, **img_out = 0; // img_in and img_out are substituted with 0 to create a double pointer
    inti = 0, j = 0; // variable for repeat statements.

    fp_in = fopen ("Lena_512.raw", "rb"); // Lena data is read in binary form and stored at the address that fp_in points to.
    if (fp_in == NULL) {
        printf("File open failed\n"); //fp_in displays the following statement when no data is entered.
    }

    img_in = (BYTE **)malloc(sizeof(BYTE*)*HEIGHT); // allocate memory to img_in in a size of 1 byte by HEIGHT.
    for (i = 0; i < HEIGH; i++) {
        img_in[i] = (BYTE *)malloc(sizeof(BYTE)*HEIGH); // One pointer in each block acts as one row and finally creates a two-dimensional array.
    }
    for (i = 0; i < HEIGH; i++) {
        Read (img_in[i], sizeof(BYTE), WIDTH, fp_in); // read data in 1byte size to img_in[i] as many times as WIDTH.
    }

    img_out = (BYTE **)malloc(sizeof(BYTE*)*HEIGHT); // memory allocation as in img_in.
    for (i = 0; i < HEIGH; i++) {
        img_out[i] = (BYTE *)malloc(sizeof(BYTE)*WIDTH);
    }
    for (i = 0; i < HEIGH; i++) {
        for (j = 0; j < WIDTH; j++) {
            Imported data from img_out[i][j] = img_in[i][j]; //img_in into img_out.
        }
    }
    fp_out = fopen("[Output]Lena(512X512).raw", "wb"); // Write the output of Lena data in binary form and open the file. And save to the address of fp_out.
    if (fp_out == NULL) {
        printf ("File open failed\n"); // The following statement appears when no data is entered. 
    }
    for (i = 0; i < HEIGH; i++) {
        fwrite(img_out[i], sizeof(BYTE), WIDTH, fp_out); //img_out's array contains the contents stored in each of the first elements in column 1 in size 512 (i.e., 512 bytes) < where fp_out points to -> [Output] Lena (512X512).Write data to raw >.
    }

    for (i = 0; i < HEIGH; i++) {
        free(img_in[i]);
        free(img_out[i]);
    }
    free(img_in);
    free(img_out);
    // Turn off dynamic assignments.
    fclose(fp_in);
    fclose(fp_out);
    // A function that closes a file after completing the operation.

    return 0;
}