Start on FILE i/O

rom/defines.s

@@ -1,20 +1,43 @@
 ; constants
-SPACE_FOR_GOSUB               := $3E
-STACK_TOP                     := $FA
-WIDTH                         := 80 ; Default terminal width
-WIDTH2                        := 70 ; mac column for zoned print
-RAMSTART2                     := $0400
+SPACE_FOR_GOSUB       := $3E
+STACK_TOP             := $FA
+WIDTH                 := 80 ; Default terminal width
+WIDTH2                := 70 ; mac column for zoned print
+RAMSTART2             := $0400
 
-BYTES_FP                      := 5
-BYTES_PER_ELEMENT             := BYTES_FP
-BYTES_PER_VARIABLE            := BYTES_FP+2
-MANTISSA_BYTES                := BYTES_FP-1
-BYTES_PER_FRAME               := 2*BYTES_FP+8
-FOR_STACK1                    := 2*BYTES_FP+5
-FOR_STACK2                    := BYTES_FP+4
+; io registers
+IO_SCREEN             := $BC00
+IO_KBD                := $BC01
+IO_ROM_BANKED_OUT     := $BC02
+IO_FILE_COMMAND       := $BC03
+IO_FILE_DESCRIPTOR    := $BC04
+IO_FILE_DATA          := $BC05
+IO_FILE_STATUS        := $BC07
 
-STACK                         := $0100
-STACK2                        := STACK
+; io commands
+IO_COMMAND_OPEN       := 1
+IO_COMMAND_CLOSE      := 2
+IO_COMMAND_SELECT_IN  := 3
+IO_COMMAND_SELECT_OUT := 4
+IO_COMMAND_READ       := 5
+IO_COMMAND_WRITE      := 6
+IO_COMMAND_RESET      := 7
+
+; io status
+FILE_STATUS_ERROR     := $01
+FILE_STATUS_EOF       := $02
+FILE_STATUS_READY     := $04
+
+BYTES_FP              := 5
+BYTES_PER_ELEMENT     := BYTES_FP
+BYTES_PER_VARIABLE    := BYTES_FP+2
+MANTISSA_BYTES        := BYTES_FP-1
+BYTES_PER_FRAME       := 2*BYTES_FP+8
+FOR_STACK1            := 2*BYTES_FP+5
+FOR_STACK2            := BYTES_FP+4
+
+STACK                 := $0100
+STACK2                := STACK
 
 
 MAX_EXPON = 10