# Extended DVI file

1. pTeX developed by ASCII corp supports vertical writing together with horisontal writing. The DVI file containing vertical writing is as follows
The last part of the DVI file are some bytes with value 243 and the value of the preceeding byte equals 3 (which is 2 in the usual case). In the page description part, the code 255 with the next code is the switch for the vertival or horizontal writing.
2. dviout supports Embedding into DVI files for any files. Embedded files are put between the page description part and PostAmbre in DVI file as follows.
PRE(247)
... % PreAmbre
BOP(139)
... % the first page
EOP(140)
...
BOP(139)
... % the last page
EOP(140)
POST(248)
data % contents of num_add files
file_name[] % num_add filenames(array of NULL terminated strings)
pt_data[num_add][bod[4], lod[4]]
% num_add pairs of the top address and length of the contens of files
bof[4] % the top address of file_name[]
eof[4] % the end address of file_name[] + 1
num_add[4] % the number of embedded files
top_add[4] % the top address of POST at the head of added part
AdID[3] % 'A', 'd', 'O' : ID
EOP(140)
POST(248)
... % PostAmbre
POST_POST(249)
top_post[4] % the address of POST at the head of PostAmbre
2 or 3, 223,...,223