How can one explain line by line this assembly language code.Detail explanations

Question

How can one explain line by line this assembly language code.Detail explanations needed.(MPLAB)

#include "p18F4520.inc"

CONFIG OSC = HS CONFIG, PWRT = OFF CONFIG, WDT = OFF CONFIG ,PBADEN = OFF, CONFIG LVP = OFF, var_a equ 0x020 ,var_b equ 0x021, org 0x000000 ,PORTS GOTO MAIN org 0x000020 MAIN CLRF TRISD BCF TRISA,RA1 BCF TRISA, RA2 ; MOVLW 0x55   BSF PORTA, RA1 call WAIT BCF PORTA, RA1 MOVLW 0xAA ;W = h'1010 1010 (d'1010') MOVWF PORTD call WAIT BCF PORTA, RA2 GOTO LOOP WAIT movlw 0x0f movwf var_b Loop2 movlw 0xff movwf var_a decfsz var_a, 1 decfsz var_b, 1 goto Loop2 return end

Explanation / Answer

* Declaration and configuration of the microcontroller *

        PROCESSOR 18F4520
        #include "p18F4520.inc"
        __CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC
       
;***** Variable declaration *****

        Cblock    0x20                   ; First free RAM location
        endc                             ; No variables
       
* Program memory structure *

        ORG       0x00                   ; Reset vector
        goto      Main                   ; After reset jump to this location
       
        ORG       0x04                   ; Interrupt vector
        goto      Main                   ; No interrupt routine
Main                                     ; Start the program
        banksel   TRISB                  ; Select bank containing TRISB
        clrf      TRISB                  ; Port B is configured as output
        banksel   PORTB                  ; Select bank containing PORTB
        movlw     0xff                   ; W=FF
        movwf     PORTB                  ; Move W to port B
Loop    goto      Loop                   ; Jump to label Loop

        End

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