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A.3 Portable File Header

Every portable file begins with a 464-byte header, consisting of a 200-byte collection of vanity splash strings, followed by a 256-byte character set translation table, followed by an 8-byte tag string.

The 200-byte segment is divided into five 40-byte sections, each of which represents the string charset SPSS PORT FILE in a different character set encoding, where charset is the name of the character set used in the file, e.g. ASCII or EBCDIC. Each string is padded on the right with spaces in its respective character set.

It appears that these strings exist only to inform those who might view the file on a screen, and that they are not parsed by SPSS products. Thus, they can be safely ignored. For those interested, the strings are supposed to be in the following character sets, in the specified order: EBCDIC, 7-bit ASCII, CDC 6-bit ASCII, 6-bit ASCII, Honeywell 6-bit ASCII.

The 256-byte segment describes a mapping from the character set used in the portable file to an arbitrary character set having characters at the following positions:

0–60

Control characters. Not important enough to describe in full here.

61–63

Reserved.

64–73

Digits ‘0’ through ‘9’.

74–99

Capital letters ‘A’ through ‘Z’.

100–125

Lowercase letters ‘a’ through ‘z’.

126

Space.

127–130

Symbols .<(+

131

Solid vertical pipe.

132–142

Symbols &[]!$*);^-/

143

Broken vertical pipe.

144–150

Symbols ,%_>?`:

151

British pound symbol.

152–155

Symbols @'=".

156

Less than or equal symbol.

157

Empty box.

158

Plus or minus.

159

Filled box.

160

Degree symbol.

161

Dagger.

162

Symbol ‘~’.

163

En dash.

164

Lower left corner box draw.

165

Upper left corner box draw.

166

Greater than or equal symbol.

167–176

Superscript ‘0’ through ‘9’.

177

Lower right corner box draw.

178

Upper right corner box draw.

179

Not equal symbol.

180

Em dash.

181

Superscript ‘(’.

182

Superscript ‘)’.

183

Horizontal dagger (?).

184–186

Symbols ‘{}\’.

187

Cents symbol.

188

Centered dot, or bullet.

189–255

Reserved.

Symbols that are not defined in a particular character set are set to the same value as symbol 64; i.e., to ‘0’.

The 8-byte tag string consists of the exact characters SPSSPORT in the portable file’s character set, which can be used to verify that the file is indeed a portable file.