In the following tables, the following symbols are used:

• <> means 'not the value or bit which follows'
• * means 'this applies to all machine with a disk drive fitted'
• b0 means bit 0
• b1 means bit 1
  …
  b15 means bit 15
• HB means 'most significant byte, hi-byte'
• LB means 'least significant byte, lo-byte'

When addresses are given in the comments, they apply to the 6128.
When the 464's address is different, it is given in brackets, such as at the comment for &B763.

Please note that this section of the guide has been set out with all the addresses in the leftmost column in the correct order for the 6128. However, a Conversion Chart specifically for the 464 is printed in Appendix C.

The area from &C000 to &FFFF is taken up by the screen memory - the layout of which is illustrated on the next page. Printed below are diagrams which show how the CPC uses the bytes of screen memory in the different MODEs. For each byte:

• in MODE 2 (where there are two colours only, each pixel needs only one bit - either on or off)

    bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
     p0   p1   p2   p3   p4   p5   p6   p7

(the pixels are arranged with p0 being the leftmost one, etc)

• in MODE 1 (where four colours are available and so two bits are needed for each pixel - 1 byte represents 4 pixels)

    bit7  bit6  bit5  bit4  bit3  bit2  bit1  bit0
    p0(1) p1(1) p2(1) p3(1) p0(0) p1(0) p2(0) p3(0)

(each pixel is twice as wide as in MODE 2)

• in MODE 0 (where sixteen colours are possible and four bits are needed for each pixel - 1 byte represents 2 pixels)

    bit7  bit6  bit5  bit4  bit3  bit2  bit1  bit0
    p0(0) p1(0) p0(2) p1(2) p0(1) p1(1) p0(3) p1(3)

(each pixel is four times as wide as in MODE 2)

NB: the numbers in brackets show which bit of the pixel's pen number the screen byte bit refers to. For example in MODE 1, the 4 most significant bits of the byte hold bit 1 of the pixel's pen value and the 41east signifcant bits hold bit 0 of the pen value.

     6128  | 464   | Size | Comments on the memory locations
     ------+-------+------+------------------------------------------
     &C000   &C000   &4000  normal (upper) screen area.  The
                              alternative (lower) screen area is from
                              &4000 to &7FFF.  The addresses of the
                              starts of lines and rows in the normal
                              screen area after a ''[[:documentations:software:locomotive.basic:start#mode|MODE]]'' instruction
                              are:

    LINE    R0W0   R0W1   R0W2   R0W3   R0W4   R0W5   R0W6   R0W7
    1       C000   C800   D000   D800   E000   E800   F000   F800
    2       C050   C850   D050   D850   E050   E850   F050   F850
    3       C0A0   C8A0   D0A0   D8A0   E0A0   E8A0   F0A0   F8A0
    4       C0F0   C8F0   D0F0   D8F0   E0F0   E8F0   F0F0   F8F0
    5       C140   C940   D140   D940   E140   E940   F140   F940
    6       C190   C990   D190   D990   E190   E990   F190   F990
    7       C1E0   C9E0   D1E0   D9E0   E1E0   E9E0   F1E0   F9E0
    8       C230   CA30   D230   DA30   E230   EA30   F230   FA30
    9       C280   CA80   D280   DA80   E280   EA80   F280   FA80
    10      C2D0   CAD0   D2D0   DAD0   E2D0   EAD0   F2D0   FAD0
    11      C320   CB20   D320   DB20   E320   EB20   F320   FB20
    12      C370   CB70   D370   DB70   E370   EB70   F370   FB70
    13      C3C0   CBC0   D3C0   DBC0   E3C0   EBC0   F3C0   FBC0
    14      C410   CC10   D410   DC10   E410   EC10   F410   FC10
    15      C460   CC60   D460   DC60   E460   EC60   F460   FC60
    16      C4B0   CCB0   D4B0   DCB0   E4B0   ECB0   F4B0   FCB0
    17      C500   CD00   D500   DD00   E500   ED00   F500   FD00
    18      C550   CD50   D550   DD50   E550   ED50   F550   FD50
    19      C5A0   CDA0   D5A0   DDA0   E5A0   EDA0   F5A0   FDA0
    20      C5F0   CDF0   D5F0   DDF0   E5F0   ED50   F550   FD50
    21      C640   CE40   D640   DE40   E640   EE40   F640   FE40
    22      C690   CE90   D690   DE90   E690   EE90   F690   FE90
    23      C6E0   CEE0   D6E0   DEE0   E6E0   EEE0   F6E0   FEE0
    24      C730   CF30   D730   DF30   E730   EF30   F730   FF30
    25      C780   CF80   D780   DF80   E780   EF80   F780   FF80

spare start C7D0   CFD0   D7D0   DFD0   E7D0   EFD0   F7D0   FFD0
 spare end  C7FF   CFFF   D7FF   DFFF   E7FF   EFFF   F7FF   FFFF

Once the whole screen has been scrolled in any direction, the above table will become incorrect. On scrolling, all the above addresses will have an offset (MOD &800) added, derived as follows:

+&02 per scroll to the left (=2, 1 or « character in MODE 2, MODE 1 or MODE 0 respectively)
-&02 per scroll to the right (=2, 1 or « character in MODE 2, MODE 1 or MODE 0 respectively)
+&50 per scroll up one line
-&50 per scroll down one line

If scrolled far enough, a screen row may sit across the boundaries of the screen memory area, whose bottom end will then wrap around to join up with the top (ie byte &FFFF will be followed by byte &C000 assuming the normal screen area). If before scrolling however, a window had been set up smaller than the whole screen then the table will remain accurate despite any scrolling.

The 'spare' areas of screen memory are filled with bytes of the relevant PAPER value each time there is a full screen CLS, and are not really available for other uses. After scrolling the spare areas may be used as screen with other bytes becoming spare.