a20 handler การใช้

• So-called A20 handlers could control the addressing mode dynamically, thereby allowing programs to load themselves into the 1024 1088 KB region and run in real mode.
• Most versions of the HIMEM . SYS extended memory driver for IBM-/ MS-DOS famously displayed upon loading a message that they had installed an " A20 handler ", a piece of software to control Gate-A20 and coordinate it to the needs of programs.