Now that you can successfully store and retrieve simple data from Program Space you want to store and retrive strings from Program Space. And specifically you want to store and array of strings to Program Space. So you start off with your array, like so:

char *string_table[] = 
{
    "String 1",
    "String 2",
    "String 3",
    "String 4",
    "String 5"
};

and then you add your PROGMEM macro to the end of the declaration:

char *string_table[] PROGMEM = 
{
    "String 1",
    "String 2",
    "String 3",
    "String 4",
    "String 5"
};

Right? WRONG!

Unfortunately, with GCC attributes, they affect only the declaration that they are attached to. So in this case, we successfully put the string_table variable, the array itself, in the Program Space. This DOES NOT put the actual strings themselves into Program Space. At this point, the strings are still in the Data Space, which is probably not what you want.

In order to put the strings in Program Space, you have to have explicit declarations for each string, and put each string in Program Space:

char string_1[] PROGMEM = "String 1";
char string_2[] PROGMEM = "String 2";
char string_3[] PROGMEM = "String 3";
char string_4[] PROGMEM = "String 4";
char string_5[] PROGMEM = "String 5";

Then use the new symbols in your table, like so:

PGM_P string_table[] PROGMEM = 
{
   string_1,
   string_2,
   string_3,
   string_4,
   string_5
};

Now this has the effect of putting string_table in Program Space, where string_table is an array of pointers to characters (strings), where each pointer is a pointer to the Program Space, where each string is also stored.

The PGM_P type above is also a macro that defined as a pointer to a character in the Program Space.

Retrieving the strings are a different matter. You probably don't want to pull the string out of Program Space, byte by byte, using the pgm_read_byte() macro. There are other functions declared in the <avr/pgmspace.h> header file that work with strings that are stored in the Program Space.

For example if you want to copy the string from Program Space to a buffer in RAM (like an automatic variable inside a function, that is allocated on the stack), you can do this:

void foo(void)
{
    char buffer[10];
    
    for (unsigned char i = 0; i < 5; i++)
    {
        strcpy_P(buffer, (PGM_P)pgm_read_word(&(string_table[i])));
        
        // Display buffer on LCD.
    }
    return;
}

Here, the string_table array is stored in Program Space, so we access it normally, as if were stored in Data Space, then take the address of the location we want to access, and use the address as a parameter to pgm_read_word. We use the pgm_read_word macro to read the string pointer out of the string_table array. Remember that a pointer is 16-bits, or word size. The pgm_read_word macro will return a 16-bit unsigned integer. We then have to typecast it as a true pointer to program memory, PGM_P. This pointer is an address in Program Space pointing to the string that we want to copy. This pointer is then used as a parameter to the function strcpy_P. The function strcpy_P is just like the regular strcpy function, except that it copies a string from Program Space (the second parameter) to a buffer in the Data Space (the first parameter).

There are many string functions available that work with strings located in Program Space. All of these special string functions have a suffix of _P in the function name, and are declared in the <avr/pgmspace.h> header file.