Microcom 412 - Manual (Page 72)

Downloadable Fonts Chapter 7
412 Operators Manual 64
The font structure consists of a set of data structures and location offsets to those structures.
All data are stored in binary form. Multi-byte values are stored least-significant-byte first. A.
Word is a 16-bit value, Byte is an 8-bit value, Label is a location within the file. The Model 412
can store a font of approximately 64KB or less in any one slot.
Label start: ;the beginning of the file
Word lookup_table_offset ;distance in bytes from start to beginning
;of lookup_table
Word tallest_char ;height of tallest char in font, in dots
Word widest_char ;width of widest char in font, in dots
Byte default_spacing ;default character spacing, usually 0
Byte byte_width ;width of all char bitmaps, in bytes
Byte first_char ;first char code in set - usually space (20h)
Byte last_char ;last char in set
Byte default_char ;what char to use if it isn't in the font
Label lookup_table ;beginning of lookup table
Word char_offset[last_char-first_char] ;array of offsets, one for each character in font.
;Each offset is the distance, in bytes, from start to
;the beginning of the corresponding character’s
;data structure. The first word in this array is the
;offset to the first character's data, the last word is
;the offset to the last character's data.
Label first_char_data ;the beginning of the first char's data structure
Word char_height ;height of this char's bitmap in dots
Word char_width ;width of this char's bitmap in dots (may be
narrower
;than the width of the bitmap_data array)
Byte bitmap_data[char_height][byte_width] ;bitmap of char, 2d array
;The most significant bit of the first byte in each
row
;prints as the rightmost dot of the character, and
the
;first row is the bottom row when printed.
Label second_char_data ;the beginning of the second char's data structure
Word char_height ;(same definition as for first char)
Word char_width ;(same definition as for first char)
Byte bitmap_data[char_height][byte_width] ;(same definition as for first char)
...
(Repeat char_data structures as needed)
...
Label last_char_data ;the beginning of the last char's data structure
Word char_height ;(same definition as for first char)
Word char_width ;(same definition as for first char)
Byte bitmap_data[char_height][byte_width] ;(same definition as for first char)