Storing values in a specific memory address in C

I'm trying out OS development and have been following a book that goes on explaining the process well, but I have come into a roadblock as the example shown doesn't work for me. The function accesses video memory 0xb8000 and gets an offset to where it stores an ascii value of a letter, followed by an attribute byte that can change it's style.

VIDEO_ADDRESS is set as #define VIDEO_ADDRESS 0xb8000 in screen.h, while the function is in screen.c

int print_char(char character, int col, int row, char attribute_byte){  unsigned char *vidmem = (unsigned char *) VIDEO_ADDRESS;  if(!attribute_byte){    attribute_byte = WHITE_ON_BLACK;  }  int offset;  if(col >= 0 && row >= 0){    offset = get_offset(col, row);  }else{    offset = get_cursor_offset();  }  if(character == '\n'){    row = get_offset_row(offset);    offset = get_offset(0, row+1);  }else{    vidmem[offset] = character;    vidmem[offset+1] = attribute_byte;  }  offset += 2;  set_cursor_offset(offset);  return offset;}

I tried another method which was combining the video address with an offset as follows:

    // vidmem[offset] = character;    // vidmem[offset+1] = attribute_byte;    char* mem = vidmem + offset;    *mem = character;    mem++;    *mem = attribute_byte;

But that leaves the top-left cell of the screen blank (calling a clear_screen() function)

get_offset() function

int get_offset(int col, int row){  return 2 * (row * MAX_COLS + col);}

clear_screen() function

void clear_screen(){  int row = 0;  int col = 0;  for(row = 0; row < MAX_ROWS; row++){    for(col = 0; col < MAX_COLS; col++){      print_char('', col, row, WHITE_ON_BLACK);    }  }  set_cursor_offset(get_offset(0, 0));}

How could I go about accessing the video memory with the offset to store the ascii value and offset?