1st 16F877A program in PICBasic

[mister_e]

yes for sure. There's many way to do that.

First of all, we will disable the PBP default configuration setting. with NOTEPAD open 16F877A.INC file in the PBP folder. It look like this

;****************************************************************
;*  16F877.INC                                                  *
;*                                                              *
;*  By        : Leonard Zerman, Jeff Schmoyer                   *
;*  Notice    : Copyright (c) 2003 microEngineering Labs, Inc.  *
;*              All Rights Reserved                             *
;*  Date      : 11/07/03                                        *
;*  Version   : 2.45                                            *
;*  Notes     :                                                 *
;****************************************************************
        NOLIST
    ifdef PM_USED
        LIST
        include 'M16F87x.INC'   ; PM header
        device  pic16F877, xt_osc, wdt_on, pwrt_on, lvp_off, protect_off
        XALL
        NOLIST
    else
        LIST
        LIST p = 16F877, r = dec, w = -302
        INCLUDE "P16F877.INC"   ; MPASM  Header
        __config _XT_OSC & _WDT_ON & _PWRTE_ON & _LVP_OFF & _CP_OFF
        NOLIST
    endif
        LIST

now place a ; in front of theses lines

device  pic16F877, xt_osc, wdt_on, pwrt_on, lvp_off, protect_off

__config _XT_OSC & _WDT_ON & _PWRTE_ON & _LVP_OFF & _CP_OFF

will look like this

;device  pic16F877, xt_osc, wdt_on, pwrt_on, lvp_off, protect_off

;__config _XT_OSC & _WDT_ON & _PWRTE_ON & _LVP_OFF & _CP_OFF

default setting are now disabled.

Now putting your configuration fuse into your program:

If you're using PM as assembler(wich is, as i remind, the default setting in MicroCode Studio) you'll add this line in your program header

@ DEVICE PIC16F877A, HS_OSC

If you get some compilation error it's because you're using MPASM as assembler so use the following

@ __config _HS_OSC

Everything is also well explain in this thread

What do different clock speeds mean? (LP,XT,HS,RC)

I hate to say that but all the explanations are in the datasheet. Different oscillator setting, different possible oscillator speed.
In your case XT is for an crystal up to 4MHZ, HS 4MHZ & up.