Screen RAM

By default, the 1 kB of screen RAM or screen memory resides in memory at 1024-2023 ($0400-$07E7).

Use in BASIC

By using the BASIC command POKE, any of the 256 chars of the C64 can be placed in the video matrix.

POKE 1024,1

This example will display the char A into the left upper corner (0 row, 0 column).

Limitations in extended color mode

By using the extended color mode the size of the character set is reduced. In this mode only 64 chars are available, because from 0, 64, 128, and 192 char value the chars (A-Z, 0-9 and punctuation marks) are printed with another background color.

Moving of screen RAM

The video matrix can be moved from its default location into other memory addresses with the following BASIC code:

POKE 53272,(PEEK(53272) AND 15) OR A

The memory that is addressed by variable A can be seen in the table below. The displaced screen memory has a handicap however, because the screen editor or the command code isn't viewable. That is a reason for using this feature only in programs.

A	Start address of screen RAM
000	0 ($0000)
016	1024 ($0400) default
032	2048 ($0800)
048	3072 ($0C00)
064	4096 ($1000)
080	5120 ($1400)
096	6144 ($1800)
112	7168 ($1C00)
128	8192 ($2000)
144	9216 ($2400)
160	10240 ($2800)
176	11264 ($2C00)
192	12288 ($3000)
208	13312 ($3400)
224	14336 ($3800)
240	15360 ($3C00)

Memory addresses

Hex Address	Dec Address	Description
Screen RAM
$0400 - $07e7	1024 - 2023	1 kB (1000 bytes) Screen RAM used for setting the characters to be displayed. The values placed in each location are "screen codes" (not PETSCII); the character displayed for a particular screen code is determined by the current character set. In the default character set values 128-255 display the same glyphs as values 0-127 but with inverted foreground and background colours. All of the character cells in the 40 columns by 25 row grid are directly accessible, e.g. POKE 1024,1 will show the character A in the left upper corner of the screen. (The color will be determined by the 4-bit value set in the Color-RAM.)
$07E8 - $07F7	2024 - 2039	unused
Sprite block register
$07F8	2040	Pointer for sprite 1 in memory block: Blockno.*64 (e.g. sprite 1 in datasette I/O buffer $033C: Blockno. = 13 (13 * 64 = 832, in hex: $0340))
$07F9	2041	Pointer for sprite 2 in memory block: Blockno.*64
$07FA	2042	Pointer for sprite 3 in memory block: Blockno.*64
$07FB	2043	Pointer for sprite 4 in memory block: Blockno.*64
$07FC	2044	Pointer for sprite 5 in memory block: Blockno.*64
$07FD	2045	Pointer for sprite 6 in memory block: Blockno.*64
$07FE	2046	Pointer for sprite 7 in memory block: Blockno.*64
$07FF	2047	Pointer for sprite 8 in memory block: Blockno.*64