Abstract:
There is disclosed a pattern output apparatus capable of easily adapting to different code systems. For this purpose conversion tables for converting from different external code systems to the internal codes are provided as a detachable memory.

Description:
This application is a continuation of application Ser. No. 08/115,122, filed Sep. 1, 1993, now abandoned, which is a continuation of application Ser. No. 07/925,355, filed Aug. 6, 1992, now abandoned, which is a continuation of Ser. No. 07/391,236, filed Aug. 9, 1989, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pattern output apparatus, and more particularly to a pattern output apparatus capable of output (display or printing) of character patterns corresponding to input character codes. 
     2. Description of the Related Art 
     In such a conventional apparatus, the input character codes are once converted into internal codes of the apparatus, and said internal codes are converted into character patterns, because this method allows easy handling of input codes of different code systems. Conventionally, the conversion to said internal codes has been conducted by a conversion program fixed in the apparatus. 
     However, it is not easy to use the apparatus in a still different code system if said conversion program is fixed. On the other hand, in order to respond to various code systems, there is required a larger amount of conversion programs, leading to a complicated control of the apparatus and an increased cost. 
     SUMMARY OF THE INVENTION 
     In consideration of the foregoing, an object of the present invention is to provide a pattern output apparatus not associated with the drawbacks of the conventional technology and enabling easy addition or alteration of the code system. 
     Another object of the present invention is to provide a pattern output apparatus capable of reading internal codes corresponding to input character codes by referring to a conversion memory, and releasing character patterns corresponding to said read internal codes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a printing apparatus embodying the present invention; 
     FIG. 2 is a view showing the memory structure of a font set 3n in the embodiment; 
     FIG. 3 is a view showing the memory structure of a code conversion table TBL 4n of said embodiment; and 
     FIG. 4 is a flow chart of a printing sequence of said embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now the present invention will be clarified in detail by embodiments thereof shown in the attached drawings. 
     FIG. 1 is a block diagram of a printing apparatus, constituting an embodiment of a pattern output apparatus of the present invention, wherein provided are a host computer 1 for sending print data (data of characters and symbols and control data) and command data to the printing apparatus of the present embodiment; a printing apparatus 2 constituting the present embodiment; an input buffer 21 for temporarily storing the data received from the host computer; a CPU 22 for controlling the printing apparatus 2; a ROM 23 storing a print control program, shown in FIG. 4, to be executed by the CPU 22; a RAM 24 to be used as a work area of the CPU 22; an output buffer 25 in which pattern data of a page are developed by the CPU 22; and an output unit 26 for forming a visible image of the pattern data of the output buffer 25 on a sheet. 
     A ROM cartridge 3 is detachably provided on the printing apparatus 2. In said ROM there are provided plural font sets 3 1  -3 n , each containing plural internal codes and font patterns corresponding to said internal codes. Also there are provided code conversion tables 4 1  -4 n  respectively for the font sets 1-n. A font set selecting switch 5 is provided. 
     FIG. 2 shows the memory structure of a font set 3n of the present embodiment. The structure is the same for the other font sets 3 1 , 3 2 , . . . . A pointer 3n-0 is provided for indicating the code conversion table 4n (TBLn). Internal codes 3n-1-3n-m respectively indicate the start addresses of the corresponding character patterns. 
     FIG. 3 shows the memory structure of a code conversion table TBL4n of the present embodiment. The structure is the same for the other tables 4 1 , 4 2 , . . . . A column 4n-1 indicates all the external code systems 1-l related to the font set n. A column 4n-2 shows internal codes corresponding to an external code 20H (H standing for hexadecimal), and stores internal codes specific to the code systems 1-l (said codes may be mutually overlapped). A column 4n-3 similarly stores internal codes corresponding to an external code 21H, respectively specific to the code systems 1-l. There are further provided similar columns up to an external code 7FH. 
     FIG. 4 is a flow chart showing the printing sequence of the present embodiment. At first a step S1 selects, for example, a font set 3n by the switch 5 whereby the code conversion table 4n is designated. The selection of the font set may also be conducted by a command (by font name or font property) from the host computer 1. A step S2 reads the column 4n-1 for a code system. A step S3 then discriminates whether the font set 3n is usable with the current external code system, namely whether said external code system is registered for the font set 3n. If not usable, a step S4 executes an exceptional process. If usable, a step S5 discriminates whether the print data are present in the input buffer 21, and, if absent, the sequence is terminated. If the print data are present, a step S6 reads said data, and a step S7 discriminates whether said data are a character code. If it is a character code, a step S8 refers to the code conversion table 4n, thus reading an internal code corresponding, in said code system, to the character code (external code). Then a step S9 reads a character pattern corresponding to said internal code, and develops said character pattern in the output buffer 25. 
     On the other hand, if the step S7 discriminates that said data are not a character code, a step S10 discriminates whether said data are a sheet discharge command. If it is a sheet discharge command, a step S11 executes sheet discharge. If not, a step S12 executes another process. 
     In the above-explained embodiment, all the internal codes for the external character codes 20H-7FH are stored on the code conversion tables, but the present invention is not limited to such form. For example it is also possible to store the basic code system in the ROM 23 and to store other code systems in the ROM 3. In this manner it is possible to reduce the memory capacity of the ROM 3. 
     It is also possible to store the control program in the ROM 3 instead of the ROM 23 as in the above-explained embodiment.