include "P16F84A.inc"
cblock 0x33
V1
V2
V3
endc
movlw 3
movwf V1
movlw 4
movwf V2
movf V1,W
addwf V2 , W
movf V2,0
movwf V3
end
Clean: Deleting intermediary and output files. Clean: Done. Executing: "C:\walaa\test.asm" /q /p16F84A "test.asm" /l"test.lst" /e"test.err" Could not spawn langauge tool. Check command-line options. (193) BUILD FAILED: Fri Dec 04 16:29:59 2020
The Original Poster does not include enough information to know for certain.
That aside, this kind of question about Microchips MPLABX has become common recently because support for the MPASMWIN assembler has been removed from MPLAX v5.40 and later.
The MPASMWIN tool chain cannot be added to these versions of the MPLABX IDE.
MPASMWIN support is present in MPLABX v5.35, the last version it was available.
The only tool chain for PIC 8-bit assembly language projects is pic-as(v2.xx).
This tool chain is part of the XC8 v2.3x C compiler installation.
Note: The pic-as(v2.3x) tool chain does not seem to be installed by default when the XC8 compiler is installed. In most cases the IDE requires the user to manually install this tool chain. That you may need to do this step is not documented by Microchip.
It would seem that Microchip's attitude is that if you are smart enough to use assembly language with obsolete controllers you should be smart enough to figure out how to install the tool chain without step by step instructions.