AMSTRAD cpc 6128 User Instruction page 199

To allocate space in the CPC612S's memory for a newly defined character, the
computer must first be prepared by issuing the command:
SYMBOL AFTER
x
.... where x is equal to or less than the character number you wish to re-define.
The command S Y M B 0 L is then issued, followed firstly by the character number x.
Regardless of whether or not the value of x specifies a character which is directly
typeable at the keyboard, the re-defined character can be printed on the screen by
issuing the command:
PRINT CHR$(x)
After S Y M B 0
L
x, there are up to S parameters which specify the S individual
horizontal rows of the character, starting from the top. Each of the parameters can be
in the range 0 to 255. The binary representation of each of the S parameters
determines the pattern of that particular row in the finished character.
For example, if the first ofthe S parameters is 1, then the top row ofthe character has
a binary representation of 00000001. Where the 1 appears, the section of the
character is printed in the PEN colour; where a 0 appears, the section of the character
is not visible because it is printed in the PA PER colour. Therefore the top row of this
newly defined character has a dot in the top right hand corner. Continuing this
example, we will specify the other 7 parameters as
3,
7 , 1 5 ,
3
1 ,
63 , 0, 0 -
the
binary representation of aIlS parameters then being:
parameter (row) 1: 00000001 binary: (decimal 1)
parameter (row) 2: 00000011 binary: (decimal 3)
parameter (row) 3: 00000111 binary; (decimal 7)
parameter (row) 4: 00001111 binary: (decimal 15)
parameter (row) 5: 00011111 binary: (decimal 31)
parameter (row) 6: 00111111 binary: (decimal 63)
parameter (row) 7: 00000000 binary: (decimal 0)
parameter (row) S: 00000000 binary; (decimal 0)
Looking at the binary representation of the above S parameters, it should be possible
to see what the shape of the new character is going to be like. Let's assign those
parameters to character number 255 using the command:
SYMBOL 255,1,3,7,15,31,63,0,0
Chapter 3 Page 80 Complete List of Keywords