Z80 Assembly 59: Console Output (Rendering Text to the Screen)
The Challenge of Text Output Displaying a single ASCII character (A′, 5′, `!′) requires the OS to perform several complex steps: Cursor Management: Find the current screen position (X, Y) where the character should appear. Font Lookup: Find the graphic pattern (the 8x8 pixel data) for that character. Drawing: Copy the font pattern onto the screen memory (Part 23). Advance Cursor: Move the cursor position to the next character cell (X+1). The PutChar Routine (System Call) Every OS provides a core routine, often called `PutChar′, which is the system call used by programs to print a single character. ...