#include <pic18f4550.h>
#include <stdint.h>

// Use this to define the interrupt vector for high-priority interrupts
void interrupt high_priority isr(void) {
    // Check if it's a PORTB change interrupt
    if (INTCON.RBIF) {
        // Handle the change here
        // Example: toggle a pin, read input, etc.

        // Clear the interrupt flag
        INTCON.RBIF = 0;
    }
}

void main(void) {
    // Set PORTB pins RB4-RB7 as input
    TRISB |= 0xF0; // Set RB4-RB7 as input (1)

    // Enable PORTB change interrupt
    INTCON.RBIE = 1;  // Enable PORTB change interrupt
    INTCON.RBIF = 0;  // Clear PORTB interrupt flag
    INTCON.GIE = 1;   // Enable global interrupts
    INTCON.PEIE = 1;  // Enable peripheral interrupts (recommended)

    // Main loop
    while (1) {
        // Your main code here (e.g., sleep, check flags, etc.)
    }
}