Filename character mapping
When dealing with "foreign" media formats, such as zip files, DOS or Unix
disks and images, etc., filenames can be encountered that contain characters
that are not allowed on BBC filing systems, or have different meanings. The
most common occurance is Unix, URLs and Zip files use / as a
directory seperator whereas the BBC uses ., and the converse
mapping of . and / as an extension seperator.
Other than DOS/Windows using \ directory seperators and
Unix/URL/ZIP using / seperators, all non-BBC filename
characters have the same meanings. The following tables show how different
special characters are mapped between BBC and non-BBC platforms.
Contents
Non-BBC to BBC
The following characters are legal in DOS/Windows or Unix/URL/ZIP filenames, but are illegal or have special meanings in BBC filenames:
Non-BBC Non-BBC BBC Replace Non-BBC BBC
Character Meaning Meaning with Example Example Notes
---------------------------------------------------------------------------------
# - wildcard ? part#3 part?3
$ - root dir < TEMP.$$$ TEMP/<<<
% - lib dir ; TEMP.%%% TEMP/;;; see notes
& - user dir + one&two one+two see notes
* wildcard wildcard * info* info*
. extension directory / help.txt help/txt
. current dir directory @ ./file @.file .\file on DOS
.. parent dir directory ^ ../menu ^.menu ..\file on DOS
: drive drive : A:file :A.file
? wildcard - # page?? page##
@ - current dir = TEMP.@@@ TEMP/=== see notes
^ - parent dir > TEMP.^^^ TEMP/>>>
/ Unix directory extension . or $ /dir/file $.dir.file
\ DOS directory - . or $ \dir\file $.dir.file
/ DOS - extension \ one/two one\two
The simplest bidirectional mapping is:
Non-BBC BBC DOS BBC Unix BBC
-----------------------------------------------
# <-> ? . -> / . <-> /
$ <-> < / -> \
^ <-> > \ -> .
BBC to Non-BBC
The following characters are legal in BBC filenames, but are illegal or have special meanings in DOS/Windows or Unix/URL/Zip filenames:
BBC BBC Non-BBC Replace BBC Non-BBC
Character Meaning Meaning with Example Example Notes
--------------------------------------------------------------------------------------
# wildcard - ? part#3 part?3
$ root dir - \ $.user \user or /unix
% lib dir - %.blib see notes
& user dir - &.mymail see notes
* wildcard wildcard * info* info*
: drive drive : :A.file A:file
< - redirection $ TEMP/<<< TEMP.$$$
> - redirection ^ TEMP/>>> TEMP.^^^
? - wildcard # why? why#
@ current dir - . @.file .\file or ./file
^ parent dir - .. ^.file ..\file or ../file
/ extension Unix directory . help/txt help.txt
. directory Unix extension / dir.file dir/file
. directory DOS extension \ dir.file dir\file
/ extension DOS - . help/txt help.txt
\ - DOS directory / one\two one/two
The simplest bidirectional mapping is:
BBC Non-BBC BBC DOS BBC Unix
-----------------------------------------------
? <-> # . -> \ . <-> /
< <-> $ \ -> /
> <-> ^ / -> .
DOS to/from UNIX
Included for completeness is mapping between DOS/Windows and Unix/URL/ZIP
filenames. Both use the same characters other than DOS/Windows using
\ for directories and UNIX/URL/ZIP using /.
DOS Unix DOS Replace DOS Unix Character Meaning Meaning with Example Example -------------------------------------------------------------------------------------- / directory - \ \dir\file.txt /dir/file.txt \ - directory / one/two.txt one\two.txt
The bidirection mapping is:
DOS Unix
---------------------
/ <-> \
Notes
- BBC
&and%would be mapped to something like$HOMEDIR$and$PATH$.
- The mapping of non-BBC
%,&and@to BBC;,+and=means that BBC;,+and=have a one-to-two non-reversable mapping.
Implementations
- RISC OS DOSFS translates bidirectionally between DOS
%,&,@and BBC;=,;~,;=. However, BBC%,&,;are also mapped to DOS%,&,;, creating a non-reversable two-to-one mapping.
- BBC DOSFS has not yet been tested.
- SparkFS Zip only maps bidirectionally between
.and/. All other mapping is Zip to BBC only, eg a Zip#is extracted as a?, but a?is stored back in a Zip unchanged as a?.
- BBCZip performs all four bidirectional character mappings
#<->?,$<-><,^<->>,.<->/.
- Other Zip implementations have not yet been tested.
SparkFS Zip
SparkFS ZIP to BBC
------------------
20_ _ 21_!_ 22_"_ 23_?_ 24_<_ 25_;_ 26_+_ 27_'_
28_(_ 29_)_ 2A_*_ 2B_+_ 2C_,_ 2D_-_ 2E_/_ 2F_._
30_0_ 31_1_ 32_2_ 33_3_ 34_4_ 35_5_ 36_6_ 37_7_
38_8_ 39_9_ 3A_:_ 3B_;_ 3C_<_ 3D_=_ 3E_>_ 3F_?_
40_=_ 41_A_ 42_B_ 43_C_ 44_D_ 45_E_ 46_F_ 47_G_
48_H_ 49_I_ 4A_J_ 4B_K_ 4C_L_ 4D_M_ 4E_N_ 4F_O_
50_P_ 51_Q_ 52_R_ 53_S_ 54_T_ 55_U_ 56_V_ 57_W_
58_X_ 59_Y_ 5A_Z_ 5B_[_ 5C_._ 5D_]_ 5E_>_ 5F___
60_`_ 61_a_ 62_b_ 63_c_ 64_d_ 65_e_ 66_f_ 67_g_
68_h_ 69_i_ 6A_j_ 6B_k_ 6C_l_ 6D_m_ 6E_n_ 6F_o_
70_p_ 71_q_ 72_r_ 73_s_ 74_t_ 75_u_ 76_v_ 77_w_
78_x_ 79_y_ 7A_z_ 7B_{_ 7C_|_ 7D_}_ 7E_~_
BBC to SparkFS ZIP
------------------
20_ _ 21_!_ 22_"_ 23_#_ 24_$_ 25_%_ 26_&_ 27_'_
28_(_ 29_)_ 2A_*_ 2B_+_ 2C_,_ 2D_-_ 2E_/_ 2F_._
30_0_ 31_1_ 32_2_ 33_3_ 34_4_ 35_5_ 36_6_ 37_7_
38_8_ 39_9_ 3A_:_ 3B_;_ 3C_<_ 3D_=_ 3E_>_ 3F_?_
40_=_ 41_A_ 42_B_ 43_C_ 44_D_ 45_E_ 46_F_ 47_G_
48_H_ 49_I_ 4A_J_ 4B_K_ 4C_L_ 4D_M_ 4E_N_ 4F_O_
50_P_ 51_Q_ 52_R_ 53_S_ 54_T_ 55_U_ 56_V_ 57_W_
58_X_ 59_Y_ 5A_Z_ 5B_[_ 5C_ D 5D_]_ 5E_>_ 5F___
60_`_ 61_a_ 62_b_ 63_c_ 64_d_ 65_e_ 66_f_ 67_g_
68_h_ 69_i_ 6A_j_ 6B_k_ 6C_l_ 6D_m_ 6E_n_ 6F_o_
70_p_ 71_q_ 72_r_ 73_s_ 74_t_ 75_u_ 76_v_ 77_w_
78_x_ 79_y_ 7A_z_ 7B_{_ 7C_|_ 7D_}_ 7E_~_
Mapping
-------
ZIP - BBC - ZIP
# -> ? -> ?
$ -> < -> <
% -> ; -> ;
& -> + -> +
. <-> /
/ <-> .
@ -> = -> =
\ -> .
^ -> > -> >
# -> error
$ -> error
% -> %
& -> error
@ -> @
\ ->
^ -> error
