C：写入视频内存

Question

I am trying to make a function that would write strings to video memory with a specific color. However, I am unable to make it work. To write single characters, i would do this:

*(char *)0xb8000 = 'O'; //Prints the letter O at the first position in video memory
*(char *)0xb8001 = 'O'; //Adds it some colors (Haven't figured how to write a byte here)

But I need to write with a variable, so I tried this but it just prints nothing.

int currentAddressVRAM = 0xb8000;

*(char *)currentAddressVRAM = 'O';
currentAddressVRAM++;

*(char *)currentAddressVRAM = 'O';
currentAddressVRAM++;

How would I do this? What am I doing wrong?

Edit: I tried this too and it just printed nothing:

char *currentAddressVRAM = (char *)0xb8000;

*currentAddressVRAM = 'O';
currentAddressVRAM++;

*currentAddressVRAM = 'O';
currentAddressVRAM++;

Answer 1

I found out how to do it finally!
Thanks for all of your helpful comments, it help me find the solution to my problem.
Here is my code :

#define VIDEO_MEMORY 0xb8000

void PrintS(char *text, char color)
{
    char *currentAddressVRAM = (char *)VIDEO_MEMORY;
    for (int i = 0; 1; i++)
    {
        if (text[i] == '\0')
        {
            break;
        }
        *currentAddressVRAM++ = text[i];
        *currentAddressVRAM++ = color;
    }
}

The only problem with this is that I don't know how to save the current address between the uses of the function. If somebody knows, please let me know!