Thread: const keyword when initialize pointers

Hello,
I have a confusion about the keyword const.


In the file header data.h I declared a structure

Code:

typedef struct
{
    int date_1;
    int date_2;
    int date_3;
}Date;

In the source file data.c, I declare 100 instances of the Date type:

Code:

Date date_000
Date date_001
Date date_002
.
.
.
Date date_099

Each instance must be passed as a parameter of a function, thus the call is made by reference.

For this I declare an array of pointers of 100 elements:

Code:

Data *dataArray[100]

Each pointer is initialized with the address of an instance:

Code:

Date *dataArray[100] = {&date_000,
                        &date_001,
                        &date_002,
                        .
                        .
                        .
                        &date_099};

The problem is that, if I do such an initialization, the code does not compile, it gives me an error.
Instead, if I initialize each pointer separately, it works.

Code:

Date *dataArray[0] = &date_000;
Date *dataArray[1] = &date_001;
Date *dataArray[2] = &date_002;
.
.
.
Date *dataArray[99] = &date_099;

Looking for information on the Internet, I understood that the initialization must be done in the following way:

Code:

Date *const dataArray[100] = {&date_000,
                              &data_001,
                              &data_002,
                              .
                              .
                              .
                              &data_099};

And, it really works.


I did not understand why the const keyword must be added?
Why array pointers must be declared const array pointers ?
What is the difference between

Code:

Data *dataArray[0] = &data_000

and

Code:

Data *const dataArray[100] = {&data_000, &data_001, &data_002, ... ,&data_099};

?


Thanks.