This document describes a password-based door locking system using an 8051 microcontroller. The system includes a keypad to enter a password, which is checked against a stored password. If the passwords match, the gate opens. Otherwise, an alarm is activated. The hardware requirements include an 8051 microcontroller, keypad, LCD, relay, motor, resistors, capacitors, crystal oscillator, voltage regulator, and momentary switch. The software includes Keil compiler, Flash Magic, and Proteus. A circuit diagram is provided. Advantages are security, low power consumption, and simple design using common components. Applications include home security and controlling access to secure areas.