Adjust code to a program which puts asterisks in all characters of the output display (rather than just the first character) when the program halts due to an error.

; Convert intext to upper case with some OS 'flavor'
 JMP UCstart
intext: DB "In Text !@#" ; Variable
 DB 0xFF ; String terminator
ucA: DB 'A' ; upper case A value
ucZ: DB 'Z' ; upper case Z value
lca: DB 'a' ; lower case a value
lcz: DB 'z' ; lower case z value
lcuc: DB 0d ; Will hold lc to uc difference
; not needed outbuf: DB 0xE8 ; output buffer start memloc
UCstart:
; Calculate the difference between lca and ucA values
; Store result in lcuc
 MOV A, [ucA]
 MOV B, [lca]
 SUB B, A
 MOV [lcuc], B
; For remainder
; reg C has the memloc of the current char
; reg B has the current output offset
; reg A has the current char ASCII value
 MOV C, intext ; Get 1st char of intext memloc
 MOV B, 0x00 ; Set output buffer offset to 0
loopch: MOV A, [C] ; Get next intext char value
 CMP A, 0xFF ; Check if string terminator
 JNE convch ; If not convert the character
 HLT ; normal termination (i.e., string terminator)
convch: CMP A, [lca] ; Is char >= lc a?
 JB showch ; If not show the char
 CMP A, [lcz] ; Is char <= lc z?
 JA showch ; If not show the char
 SUB A, [lcuc] ; Subtract to convert to upper case
showch: MOV [OBchar], A ; 'Pass' the ASCII character
 MOV [OBloc], B ; 'Pass' the buffer offset 
 CALL OBch ; Have the 'OS' output the character
 INC B ; increment output buffer memloc
 INC C ; increment intext memloc
 JMP loopch ; process next character
; OS code
OBbeg: DB 0xE8 ; Output buffer begin location
OBend: DB 0xFF ; Output buffer end location
OBchar: DB 0x00 ; Passed ASCII character to output
OBloc: DB 0x00 ; Passed output buffer offset
 
OBch:
 PUSH A ; preserve reg A value
 PUSH B ; preserve reg B value
 MOV A, [OBchar] ; get the 'passed' char in reg A
 MOV B, [OBloc] ; get the 'passed' buffer offset
 ADD B, [OBbeg] ; Calc output buffer location
 CMP B, [OBbeg] ; Check if location >= OB begin loc
 JB OBErr ; If not jump to error
 CMP B, [OBend] ; Check if location <= OB end loc
 JA OBErr ; if not jump to error
 MOV [B], A ; put character into output buffer
 POP B ; restore reg B
 POP A ; restore reg A
 RET
OBErr: ; Invalid output attempted
; a 'real' OS would have the app exit with an error code
 MOV B, [OBbeg] ; Get loc of output buffer
 MOV [B], '*' ; put an * to indicate an issue
 HLT ; error termination