Workspaces: ZP

       Name: ZP                                                      [Show more]
       Type: Workspace
    Address: &0080 to &0089
   Category: Workspaces
    Summary: Important variables used by the I/O processor
    Context: See this workspace in context in the source code
 Variations: See code variations for this workspace in the different versions
 References: No direct references to this workspace in this source file


 ORG &0080

.ZP

 SKIP 0                 \ The start of the zero page workspace

.P

 SKIP 1                 \ Temporary storage, used in a number of places

.Q

 SKIP 1                 \ Temporary storage, used in a number of places

.R

 SKIP 1                 \ Temporary storage, used in a number of places

.S

 SKIP 1                 \ Temporary storage, used in a number of places

.T

 SKIP 1                 \ Temporary storage, used in a number of places

.SWAP

 SKIP 1                 \ Temporary storage, used to store a flag that records
                        \ whether or not we had to swap a line's start and end
                        \ coordinates around when clipping the line in routine
                        \ LL145 (the flag is used in places like BLINE to swap
                        \ them back)

.T1

 SKIP 1                 \ Temporary storage, used in a number of places

.COL

 SKIP 1                 \ Temporary storage, used to store colour information
                        \ when drawing pixels in the dashboard

.OSSC

 SKIP 2                 \ When the parasite sends an OSWORD command to the I/O
                        \ processor (i.e. an OSWORD with A = 240 to 255), then
                        \ the relevant handler routine in the I/O processor is
                        \ called with OSSC(1 0) pointing to the OSWORD parameter
                        \ block (i.e. OSSC(1 0) = (Y X) from the original call
                        \ in the I/O processor)

 ORG &0090

.XX15

 SKIP 0                 \ Temporary storage, typically used for storing screen
                        \ coordinates in line-drawing routines
                        \
                        \ There are six bytes of storage, from XX15 TO XX15+5.
                        \ The first four bytes have the following aliases:
                        \
                        \   X1 = XX15
                        \   Y1 = XX15+1
                        \   X2 = XX15+2
                        \   Y2 = XX15+3
                        \
                        \ These are typically used for describing lines in terms
                        \ of screen coordinates, i.e. (X1, Y1) to (X2, Y2)
                        \
                        \ The last two bytes of XX15 do not have aliases

.X1

 SKIP 1                 \ Temporary storage, typically used for x-coordinates in
                        \ line-drawing routines

.Y1

 SKIP 1                 \ Temporary storage, typically used for y-coordinates in
                        \ line-drawing routines

.X2

 SKIP 1                 \ Temporary storage, typically used for x-coordinates in
                        \ line-drawing routines

.Y2

 SKIP 1                 \ Temporary storage, typically used for y-coordinates in
                        \ line-drawing routines

 SKIP 2                 \ The last 2 bytes of the XX15 block

.SC

 SKIP 1                 \ Screen address (low byte)
                        \
                        \ Elite draws on-screen by poking bytes directly into
                        \ screen memory, and SC(1 0) is typically set to the
                        \ address of the character block containing the pixel
                        \ we want to draw

.SCH

 SKIP 1                 \ Screen address (high byte)