Method and apparatus for transforming PRESTEL codes to NAPLPS codes

DETAILED DESCRIPTION Accordingly, it is an object of the invention to provide an apparatus for converting PRESTEL codes to NAPLPS codes.
It is another object of the invention to provide such apparatus in which PRESTEL codes are transformed to NAPLPS codes with a simple procedure.
It is a further object of the present invention to easily convert the PRESTEL code to the NAPLPS code by only adding PRESTEL decoder hardware in a NAPLPS terminal.
In the apparatus of this invention, an input PRESTEL code is identified as to whether it is a control code, an attribute code, or a character code.
If the identified code is a control code, a corresponding NAPLPS code is output from the Co set from the in-use table.
For an attribute code, it is further determined whether the code designates an alphanumeric character or a mosaic character of the NAPLPS primary character set or the mosaic set which are registered for example in the G.
sub.
0 and G.
sub.
1 of G set, respectively, and if so, such character is invoked to the in-use table by the locking shift code.
If the attribute code designates a color of the following character, the PDI (Picture Description Instruction) set, which is registered for example to G.
sub.
2 of G set, is invoked temporarily to the in-use table by the single shift character and a color select code and a color code which represent the same color as what is defined by the attribute code.
In case of a character code, a corresponding code is output from a primary character set or a mosaic set which was already invoked to the in-use-table by the locking shift character.
Accordingly, PRESTEL codes are transformed to NAPLPS codes.
These features and advantages of the present invention will become more apparent upon a perusal of the following specification taken in conjunction with the accompanying drawings wherein similar characters of reference refer to similar structures in each of the separate views.