Please explain about this program

[wafagenius]

I need someone to help me explain about this program and tell me if there is error occur. I will attached the circuit altogether if someone know about the circuit error if any.I am new in picbasic and electronic,I beg all expert out there, please help me......!

' PicBasic Pro program
' 10-bit A/D conversion
' Balancing robot using Sharp GP2D12
' Use a 16f876 pic mcu from microchip

define osc 20
' Define ADCIN parameters
Define ADC_BITS 10 ' Set number of bits in result was 10
Define ADC_CLOCK 3 ' Set clock source (3=rc)
Define ADC_SAMPLEUS 50 ' Set sampling time in uS was 50
define DEBUG_REG PORTB
define DEBUG_BIT 5
define DEBUG_BAUD 9600
define DEBUG_MODE 1
define DEBUG_PACING 500


tiltfor var word ' ET Sensor Forward
tiltbac var word ' ET sensor Back
lwheel var word ' Left wheel zero speed
rwheel var word ' Right wheel zero speed
speed var word ' speed variable
k con 7 ' k factor
smax con 500 ' speed limiter

TRISA = %11111111 ' Set PORTA to all input
ADCON1 = %10000010 ' Set PORTA analog and right justify result


'lwheel=747 'zero calibrate left wheel
'rwheel=747 'zero calibrate right wheel

speed=0
start:

debug "Balbot ET"
pause 1000
high portc.2
pause 1000
low portc.2

adcin 1, lwheel 'read trimmer for left wheel zero speed

adcin 2, rwheel 'read trimmer for right wheel zero speed

loop:

adcin 0, tiltfor ' Read channel 0 to adval

adcin 4, tiltbac

speed = abs (tiltfor - tiltbac)* k

if speed > smax then speed = smax

if tiltbac > tiltfor then back


forward:

low portc.0
pulsout portc.0,(lwheel + speed) 'left wheel
pause 5
low portc.1
pulsout portc.1,(rwheel - speed) 'right wheel
pause 5

goto loop

back:

low portc.0
pulsout portc.0,(lwheel - speed) 'left wheel
pause 5
low portc.1
pulsout portc.1,(rwheel + speed) 'right wheel
pause 5

goto loop

End