void mainentry() {
    int x = 5;

    char* video_memory = (char*) 0xb8000;
    *video_memory = 'X';

    // Here , the star following the type means that this is not a variable to hold
    // a char (i.e. a single byte ) but a pointer to the ADDRESS of a char ,
    // which , being an address , will actually require the allocation of at least
    // 32 bits .
    char * video_address = (char*)(0xb8000);
    // If we ’d like to store a character at the address pointed to , we make the
    // assignment with a star - prefixed pointer variable . This is known as
    // dereferencing a pointer , because we are not changing the address held by
    // the pointer variable but the contents of that address .
    *video_address = 'x';
    // Just to emphasise the purpose of the star , an ommision of it , such as:
}