Switch Interfacing Program with PIC16F877A

#include <p18f2520.h>

#pragma config OSC    = XT  // 4MHz Crystal, (XT oscillator)
#pragma config PBADEN = OFF // PORTB<4:0> pins are configured as digital I/O on Reset)


void delay_ms(unsigned int duration);
unsigned char is_sw1_pressed(void);
unsigned char is_sw2_pressed(void);


void main()
{
   TRISCbits.TRISC0=0; // Set PortC bit 0 as output, LED1 is connected to thi pin
   TRISCbits.TRISC1=0; // Set PortC bit 0 as output, LED2 is connected to thi pin
    
   LATCbits.LATC0=0; // turn off LED1
   LATCbits.LATC1=0; // turn off LED2

   TRISBbits.TRISB3=1; // configure SW1 pin as input
   TRISBbits.TRISB4=1; // configure SW2 pin as input
    
    while(1)
    {
      if(is_sw1_pressed()==1)    // is key 1 pressed
      {                        // yes
         LATCbits.LATC0=1;     // turn ON LED1    
        }
        else
        {                        //no
            LATCbits.LATC0=0;    //turn off LED1
        }

        if(is_sw2_pressed()==1)    // is key 2 pressed
        {                        // yes
            LATCbits.LATC1=1;     // turn ON LED2    
        }
        else
        {                        //no
            LATCbits.LATC1=0;    //turn off LED2
        }
    }
}

/////////////////////////////////////////////////////////////////////////////////////////
//     this is delay routine
//     input: required Delay duration in mili Seconds
//    output: none
/////////////////////////////////////////////////////////////////////////////////////////

void delay_ms(unsigned int duration) // delay in miliseconds for 4.0MHZ crystal
{
    unsigned int i;
    for(;duration!=0;duration--)
    {
        for(i=0;i<=50;i++)
        {
            _asm
                nop
                nop
                nop
            _endasm
        }
        _asm
            nop
            nop
        _endasm
    }
}


/////////////////////////////////////////////////////////////////////////////////////////
//this routine is to check key1 pressings.
//input: none 
//output: 0 if switch is not pressed. 1 if switch is pressed. 
/////////////////////////////////////////////////////////////////////////////////////////
unsigned char is_sw1_pressed(void)
{
    if (PORTBbits.RB3==0)        // is SW1 pressed?
    {                            //yes
        delay_ms(10);            // wait 10mS for debounce.
        if (LATBbits.LATB3==0)    // is SW1 still has pressed status after 10mS delay?
        {                        // yes, we have key press
            return 1;
        }
    }
    return 0;// if key is not pressed, return 0
}

/////////////////////////////////////////////////////////////////////////////////////////
//this routine is to check key2 pressings.
//input: none 
//output: 0 if switch is not pressed. 1 if switch is pressed. 
/////////////////////////////////////////////////////////////////////////////////////////
unsigned char is_sw2_pressed(void)
{
    if (LATBbits.LATB4==0)        // is SW1 pressed?
    {                            //yes
        delay_ms(10);            // wait 10mS for debounce.
        if (LATBbits.LATB4==0)    // is SW1 still has pressed status after 10mS delay?
        {                        // yes, we have key press
            return 1;
        }
    }
    return 0;// if key is not pressed, return 0
}