Real Mode Assembly: Print Char to Screen without INT Instruction on Boot

Question

The following site \"Writing Boot Sector Code\" provides a sample of code that prints \'A\' to the screen when the system boots. From what I have been reading don\'t you have to

Answer 1

At boot, you're in a default screen mode - in this case a text screen mode. Your example program is writing directly into the character buffer that's displayed on the screen for that text screen mode. Setting the data segment register to 0xb800 is getting things set up to point at that buffer. Check out this tutorial for more information.