Word processor for selecting a control program stored in the word processor when a control program in an externally detachable memory is not able to be read
This application is a continuation of application Ser. No. 621,693 filed Jun. 18, 1984, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a word processor for processing words under control of a program read from an exchangeable storage, and more particularly to a word processor for processing words even if there is trouble in reading the program from the exchangeable storage. 
     2. Description of the Prior Art 
     In a prior art word processor which stores a control program in an exchangeable storage, such as a floppy disc, to process words, it is not at all possible to process the words when there is a trouble in reading out the program from the storage such as the floppy disc. For example, if the floppy disc which contains a word processing program is not loaded in a disc drive or there is a fault in reading out the floppy disc, the word processor is totally inoperable. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a word processor which contains a large volume of word processing programs in an exchangeable storage such as a floppy disc and has a small capacity storage which contains a portion of the word processing programs to enable the word processor to temporarily process the words even if the exchangeable storage is not loaded or there is a failure in reading out the exchangeable storage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a configuration of a word processor of the present invention, and 
     FIG. 2 is a flow chart showing an operation of the word processor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of a configuration of the word processor of the present invention is shown in FIG. 1. A control unit (MPU) 1 controls a word processing operation such as information input/output or an edition for processing words in accordance with controlling and processing programs read from a read-only memory (ROM) 2 or a readable and writable memory (RAM) 4. The memory contain programs for controlling respective units of the word processor and operations of those units. A read-only memory (ETW-ROM) 3 contains a small portion of the word processing program sufficient to control only frequently used major ones of the word processings. To input information for the word processings, inputs from a keyboard (KBD) 5 are controlled by a keyboard controller (KBD-C) 6. Inputs from a floppy disc drive (FDD) 7, which reads information from an exchangeable floppy disc that contains a large volume of word processing programs sufficient to control all necessary word processings and is loaded to the floppy disc drive (FDD) 7, are controlled by a floppy disc drive controller (FD-C) 8. On the other hand, to output the information, a display output by a cathode ray tube display (CRT) 9 is controlled by a CRT controller (CRT-C) 10 and a print output by a printer (PRTR) 11 is controlled by a printer controller (PRT-C) 12. 
     FIG. 2 shows a flow chart illustrating a manner of a word processing operation of the word processor of the present invention. In the flow chart of FIG. 2, when a power is turned on, the control of the word processing operation is started by the control unit (MPU) 1 in accordance with the control procedures of the program stored in the read-only memory (ROM) 2. In a step S1, it is checked by the information from the floppy disc controller (FD-C) 8 whether or not the floppy disc drive (FDD) 7 is ready to read the information from the floppy disc, and if it is not ready, the program proceeds to a step S2. In the step S2, &#34;Operation in typewriter mode&#34; is displayed on the CRT 9, and in a step S6 the temporary word processing operation is started in accordance with the second word processing program which controls only a portion of the word processings and is stored in the read-only memory (ETW-ROM) 3. The second word processing program stored in the read-only memory (ETW-ROM) 3 is a temporary program for controlling relatively simple word processing functions such as an electronic typewriter function in which a character corresponding to a depressed key on the keyboard (KBD) 5 is outputted to the printer (PRTR) 11, and it cannot control complex word processing functions. However, it is effective to avoid stoppage of the functions of the word processor even when there is a failure in reading out the major word processing programs. 
     On the other hand if it is determined in the step S1 that the floppy disc drive (FDD) 7 is ready to read the floppy disc, the program proceeds to a step S3 where the data is read from the floppy disc, and in a step S4 the control unit (MPU) 1 determines if the data read from the floppy disc is the word processing program and if the floppy disc currently loaded is the word processing system floppy disc. If the data read from the floppy disc is not the word processing program, the program proceeds to the step S2 where a temporary word processing operation, similar to that carried out when the floppy disc cannot be read, is effected. 
     In the step S4, if it is determined that the floppy disc currently loaded is the word processing system floppy disc, the program proceeds to a step S5 where the word processing system is loaded to the writable memory (RAM) 4 and the predetermined word processing operation is started. 
     As described hereinabove, according to the present invention, when the system floppy disc which contains the word processing programs capable of controlling all predetermined word processings is not loaded in the word processor or the floppy disc cannot be read out because of a failure or when an address of a letter is to be printed with an increased voltage, the temporary program is read from the memory of the word processor so that the frequently used word processing operations can be carried out. Accordingly, the total stoppage of the function of the word processor is avoided.