It is important to know what character set is being used by the programs you are writing.
True ASCII values run from 00 to 7F, hexadecimal. The values 00 to 1F, and 7F, are control characters, while those from 20 to 7E are printable ASCII characters.
The extended character set has the values 80 to FF. These are all printable characters in MSDOS.
Create the table below. The high-order nibble of the value is the row label, while the low-order nibble is the column label. Thus, the value for the character 'A' is 41.
To make your job easier, use this const section.
const Heading = 'Extended ASCII Chart';
HeadingColor = Yellow;
LabelColor = White;
CharColor = Red;
HexDigits : array[0..15] of char= '0123456789ABCDEF';
NonPrintables = [ 7, 8, 10, 13];
FieldWidth = 3;
The HexDigits constant is an array of chars which you should use for printing your column and row labels.
The NonPrintables are characters which cannot be printed to the screen. Use the in operator to see if the char you are trying to print is actually printable.