;ctype.h02 assembly language subroutines
;
;C02 Functions modify Accumulator and Flags
;  ISxxxx will load $FF into Accumulator to and Set Carry if True
;          and load $00 into Accumulator to and clear Carry if False
;  toxxxx set Carry if character is converted, otherwise clear Carry 
;Machine Language Subroutines modify Flags but not Accumulator
;  Carry will be Set if True and Cleared if False 
;Index Registers X an Y are not modified by any routines

        SUBROUTINE CTYPE

;Character Test Functions - Set Accumulator
ISALNM: JSR ISALN   ;Is Alphanumeric Character
        BVC .ISBTF
ISALPH: JSR ISALP   ;Is Alphabetic Character
        BVC .ISBTF
ISBDGT: JSR ISBIN   ;Is Binary Digit 
        BVC .ISBTF
ISCTRL: JSR ISCTL   ;Is Control Character
        BVC .ISBTF
ISDIGT: JSR ISDGT   ;Is Digit
        BVC .ISBTF
ISGRPH: JSR ISGRP   ;Is Graphical Character
        BVC .ISBTF
ISHDGT: JSR ISHEX   ;Is Hex Digit 
        BVC .ISBTF
ISLOWR: JSR ISLWR   ;Is Lowercase Character
        BVC .ISBTF
ISPNCT: JSR ISPNC   ;Is Punctuation Character
        BVC .ISBTF
ISPRNT: JSR ISPRT   ;Is Printable Character
        BVC .ISBTF
ISSPCE: JSR ISSPC   ;Is White Space Character
        BVC .ISBTF
ISUPPR: JSR ISUPR   ;Is Uppercase Character
        BVC .ISBTF

;Internal Routines - Set Accumulator based on Carry Flag
.ISBTF  BCC .ISFLS   ;If Carry Set
.ISTRU  LDA #$FF    ;  Return TRUE
        RTS         ;Else 
.ISFLS  LDA #$00    ;  Return FALSE
        RTS

;C02/ML Character Conversion Routines
TOLOWR: JSR ISUPR   ;If Char IS Not Upper Case
        BCC .ISRTS  ;  Return
        ORA #$20    ;Else Set Bit 5 
        RTS         ; and Return

TOUPPR: JSR ISLWR   ;If Char IS Not Lower Case
        BCC .ISRTS  ;  Return
        AND #$DF    ;Else Clear Bit 5 
        RTS         ; and Return

;Machine Language Subroutines - Set/Clear Carry, Preserve Accumulator 
ISALN:  JSR ISDGT  ;If Char IS Digit
        BCS .ISRTS  ;  Return Carry Set
                    ;Else
ISALP:  JSR ISUPR  ;If Char IS Upper Case
        BCS .ISRTS  ;  Return Carry Set
                    ;Else
ISLWR:  CMP #$61    ;If Char < 'a'
        BCC .ISRTS  ;  Return with Carry Clear
        CMP #$7B    ;Else If Char >= '{'
        JMP ISBCS   ;  Return with Carry Clear Else Return with Carry Set

ISUPR:  CMP #$41    ;If Char < 'A'
        BCC .ISRTS  ;  Return with Carry Clear
        CMP #$5B    ;Else If Char >= '['
ISBCS:  BCS .ISCLC  ;  Return with Carry Clear
        BCC .ISSEC  ;Else Return with Carry Set

.ISSEC  SEC         ;Set Carry
        BCS .ISRTS  ;  and Return

.ISCLC  CLC         ;Clear Carry
.ISRTS  CLV         ;Clear Overflow - for C02 calls
        RTS         ;Return from Subroutine

ISCTL:  CMP #$7F    ;If Char = DEL
        BEQ .ISSEC  ;  Return Carry Set
        CMP #$20    ;Else If Char < ' '
        JMP ISBCS   ;  Return Carry Set Else Return Carry Clear

ISBIN:  CMP #$32    ;If Char >= '2'
        BCS .ISCLC  ;  Return Carry Set
                    ;Else
ISDGT:  CMP #$30    ;If Char < '0'
        BCC .ISRTS  ;  Return Carry Clear
        CMP #$3A    ;Else If Char >= ':'
        JMP ISBCS   ;  Return FALSE Else Return TRUE

ISPNC:  JSR ISALN  ;If Char IS Alphanumeric
        BCS .ISCLC  ;  Return Carry Clear
                    ;Else
ISGRP:  CMP #$20    ;If Char IS Space
        BEQ .ISCLC  ;  Return Carry Clear
                    ;Else
ISPRT:  CMP #$80    ;If Char IS High ASCII
        BCS .ISCLC  ;  Return Carry Clear 
        JSR ISCTL   ;If Char IS Not Control
        JMP ISBCS   ;  Return Carry Clear Else Return Carry Set

ISSPC:  CMP #$20    ;If Char IS ' '
        BEQ .ISSEC  ;  Return Carry Set
        CMP #$09    ;If Char < '\t'
        BCC .ISRTS  ;  Return Carry Clear
        CMP #$0E    ;Else If Char > '\r'
        JMP ISBCS   ;  Return Carry Clear Else Return Carry Set

ISHEX:  CMP #$41    ;If Char < 'A'
        BCC ISDGT   ;  Check for Digit
        CMP #$47    ;Else If Char < 'G'
        BCC .ISSEC  ;  Return Carry Set
        CMP #$61    ;Else If Char < 'a'
        BCC .ISRTS ;   Return Carry Clear
        CMP #$67    ;Else If Char >= 'g'
        JMP ISBCS   ;  Return Carry Clear Else Return Carry Set

        ENDSUBROUTINE