Fixed backspace in basic

apps/basic/basic.asm

@@ -13,6 +13,7 @@
 ;    - fixed ram size instead of poking at ram locations
 ;    - BIOS calls instead of using RST
 ;    - Unsupported functions cause FCERR, not a reset or REM
+;    - modern backspace handling
 ;
 ;==================================================================================
 ; The updates to the original BASIC within this file are copyright Grant Searle
@@ -52,7 +53,7 @@ MC_RAM_END              .EQU    0FFFFH
 
 CTRLC   .EQU    03H             ; Control "C"
 CTRLG   .EQU    07H             ; Control "G"
-BKSP    .EQU    7FH             ; Back space
+BKSP    .EQU    08H             ; Back space
 LF      .EQU    0AH             ; Line feed
 CS      .EQU    0CH             ; Clear screen
 CR      .EQU    0DH             ; Carriage return
@@ -62,7 +63,7 @@ CTRLR   .EQU    12H             ; Control "R"
 CTRLS   .EQU    13H             ; Control "S"
 CTRLU   .EQU    15H             ; Control "U"
 ESC     .EQU    1BH             ; Escape
-DEL     .EQU    08H             ; Delete
+DEL     .EQU    7fH             ; Delete
 
 ; BASIC WORK SPACE LOCATIONS
 
@@ -942,10 +943,25 @@ ECHDEL: DEC     B               ; Count bytes in buffer
         CALL    OUTC            ; Echo it
         JP      MORINP          ; Get more input
 
-DELCHR: DEC     B               ; Count bytes in buffer
-        DEC     HL              ; Back space buffer
-        CALL    OUTC            ; Output character in A
-        JP      NZ,MORINP       ; Not end - Get more
+DELCHR: ;DEC     B               ; Count bytes in buffer
+        ;DEC     HL              ; Back space buffer
+        ;CALL    OUTC            ; Output character in A
+        ;JP      NZ,MORINP       ; Not end - Get more
+        LD      A,B
+        CP      1
+        JP      Z,MORINP
+        DEC     B
+        DEC     HL
+        LD      A,(CURPOS)
+        DEC     A
+        LD      (CURPOS),A
+        LD      A,BKSP
+        CALL    MONOUT
+        LD      A,' '
+        CALL    MONOUT
+        LD      A,BKSP
+        CALL    MONOUT
+        JP      MORINP
 OTKLN:  CALL    OUTC            ; Output character in A
 KILIN:  CALL    PRNTCRLF        ; Output CRLF
         JP      TTYLIN          ; Get line again
@@ -958,7 +974,8 @@ TTYLIN: LD      HL,BUFFER       ; Get a line by character
 MORINP: CALL    CLOTST          ; Get character and test ^O
         LD      C,A             ; Save character in C
         CP      DEL             ; Delete character?
-        JP      Z,DODEL         ; Yes - Process it
+        ;JP      Z,DODEL         ; Yes - Process it
+        JP      Z,DELCHR
         LD      A,(NULFLG)      ; Get null flag
         OR      A               ; Test null flag status
         JP      Z,PROCES        ; Reset - Process character