⏰ 8086 Real-Time Clock Display

A real-time clock rendered directly to VGA text-mode video memory on the Intel 8086 processor, written in TASM (Turbo Assembler).

The clock displays HH:MM:SS in the bottom-right corner of the screen, with each component in a different color:

Component	Color
Hours	Green
Minutes	Blue
Seconds	Red
Colons	Black

All text is rendered on a white background. The display updates every second and exits on any keypress.

How It Works

• Time is read via DOS interrupt int 21h (function 2Ch)
• Output is written directly to VGA text memory at segment 0B800h using the stosw string instruction — each call writes a character + color attribute and auto-increments the pointer
• The main loop polls for time changes and only redraws when the second value changes, avoiding unnecessary writes to video memory
• Keyboard input is checked via int 16h (function 01h) in a non-blocking manner

Build & Run

Requirements

• TASM (Turbo Assembler)
• TLINK (Turbo Linker)
• DOS environment or DOSBox

Commands

tasm clock.asm
tlink clock.obj
clock.exe

Press any key to exit.

Project Structure

├── clock.asm    — main source file
└── README.md