JPH0467223B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention makes it possible to access a data file created in an external storage device of a computer of a terminal station from a computer of another terminal station even while a computer of a terminal station is executing a certain job. This invention relates to a computer communication system.

[Prior art]

In conventional computer communication systems, a simple computer called a personal computer is used alone or connected to a large computer installed at a center via a communication network and used as a terminal for the computer at the center. was. When used as a communication terminal, it is specialized for sending and receiving data to and from the center computer, and while the end station is executing its own job, it is possible to perform data communication in parallel with the execution of that job. I couldn't do it. There are also personal computers that have communication functions, but normally two personal computers must be connected directly or via a telephone line, and a dedicated communication control program must be loaded and executed on the two personal computers. For example, data cannot be sent or received. For this reason, currently, each terminal station's computer holds its own data file, and even when that terminal station's computer is executing an arbitrary job, that data file can be freely accessed from the computers of other terminal stations. There is no network system in which personal computers can read and write data.

[Problems to be solved by the invention]

Therefore, if the personal computer of one terminal station is executing one job and the personal computer of another terminal station requests data transmission/reception, the job must be temporarily interrupted and the job executed. , it was necessary for both personal computers to load a communication control program to communicate with the other personal computer. In addition, starting communication for mutual communication had to be carried out by telephone communication between operators. In addition, since it is not possible to construct a computer network system that is organically connected as described above,
The disadvantage was that the data files held at each terminal station could not be used effectively. For this reason, there is waste in data file management, as the external storage medium itself containing the data file must be moved between each terminal station, or each terminal station must hold the same data file.

[Means to solve the problem]

The configuration of the invention for solving the above problems includes a computer having an external storage device in which data files are formed, a keyboard for inputting data, a central processing unit, and a transmitting/receiving buffer for inputting data transmitted and received between terminal stations. , a terminal station comprising a serial interface that converts output data of the computer into a serial signal, and a modem that modulates and demodulates between the serial signal and the analog signal, and the modems of the plurality of terminal stations are connected. It comprises a coaxial transmission line, and a frequency conversion device connected to the transmission line and converting a transmission frequency band output from the terminal station into a reception frequency band, and in the computer, between the transmission and reception buffers of each terminal station. a communication control means for transmitting and receiving data as a background job by interrupt processing; and a communication control means for determining whether there is reception data in the transmitting/receiving buffer in the process of executing reading processing of key code data input by the computer from the keyboard. , and key input control means for accessing the data file according to the received data and exchanging data between the transmission/reception buffer and the data file.

[Effect]

In the coaxial transmission line of the above-mentioned communication system, two-way communication between terminal stations is made possible by separating frequency bands for transmission and reception. A frequency modulated signal in a transmission band sent from a terminal station is converted into a signal in a frequency in a reception band by a frequency conversion device connected to a coaxial transmission line, and can be received by each terminal station. The communication control means transmits and receives data between the transmitting and receiving buffers of each terminal station as a background job using interrupt processing. Further, the key input control means determines the presence or absence of received data in the transmission/reception buffer in the process of reading the key code data input by the computer from the keyboard, accesses the data file according to the received data, and performs the transmission/reception. Data is exchanged between buffer and data file. In the basic input/output routine that reads key data input from the keyboard, the basic input/output routine that accesses the file is not started, and the file that was accessed before the basic input/output routine that reads the key data is executed is closed. It is in a state of Therefore, in such an operating system, when a basic input/output routine that reads this key data is executed while a computer at one end station is executing a job, the data file of that computer is transferred to another computer. It can be accessed from any computer. Therefore, in the present invention, in the process of reading key code data input from the keyboard, the computer determines the presence or absence of received data in the transmitting/receiving buffer, accesses the data file according to the received data, and transfers the data to the transmitting/receiving buffer. By providing a key input control means for exchanging data between data files, when the computer of one terminal station A becomes ready to input data from the keyboard while executing a certain job, it is possible to input data via the coaxial transmission line. from the computer of another terminal B,
Reading and writing data to a file on the computer of terminal station A can be executed in parallel with key input processing on the computer of terminal station A. In the process of reading key data input by the operator, there is a lot of waiting time for key input, so the CPU
From the looks of it, there is a lot of free time.
Therefore, in the process of executing the above key code data reading process, it is possible to determine the presence or absence of data in the transmission/reception buffer and to transfer a certain length of data between the file and the transmission/reception buffer. Therefore, by reducing the length of data transferred at one time between the file and the sending/receiving buffer, the file can be accessed from a computer at another terminal station during key input processing without reducing the key data input speed by the operator. becomes.

【Example】

The present invention will be described below based on specific examples. FIG. 1 is a block diagram of a computer communication system according to a specific embodiment of the present invention. A1 to An are central processing units (hereinafter referred to as "CPU"), and B1 to Bn are connected to the CPU.
It is an interface of RS232C standard, and C1 to Cn
is a modem (modulator/demodulator) connected to the coaxial transmission line D, and E is a frequency converter that converts a low frequency band to a high frequency band. In addition, each CPUA1~An
are connected to disk drive devices F1 to Fn, and disks G1 to Gn are mounted on the disk drive devices F1 to Fn.
A data file has been created in ~Gn. Each modem has a transmission band in the low group and a reception band in the high group. Therefore, the signal output in the low band is frequency-converted by the frequency conversion device E to the high band, and can be received by each modem. The line connection method is performed in the following steps. Assume that CPUA1 is the transmitting terminal station. From CPUA1
When the transmission request signal RS is output to the modem C1 via the RS232C interface B1, the modem determines whether there is a carrier in the low group on the transmission path D, and if a carrier exists, the transmission path D is used. Since the transmission request signal RS is in the middle, the transmission request signal RS is rejected. Also,
If there is no low group carrier on the transmission path D, the low group carrier is sent to the transmission path D, and the carrier is converted by the frequency conversion device E into a high group carrier. When each modem C1 to Cn receives a large number of carriers, data cannot be transmitted from any modem other than modem C1. Moreover, when the modem C1 receives a high number of carriers, it outputs a transmittable signal CS to the CPUA1 via the RS232C interface B1. When this state is reached, the terminal station of CPUA1 has acquired the right to transmit to transmission path D, and cannot transmit from other terminal stations. Next, the data frame specifying the address of the receiving station is output from the terminal station of CPUA1 via the transmission/reception buffer, and the data frame is received by the specified destination station, for example, the terminal station of CPUA3. input into the transmit/receive buffer of Next, when the data transmission of CPUA1 is completed,
The transmission request signal RS is turned off, the low group carriers are eliminated, and the transmission path D is opened. And CPUA1
The terminal station of CPUA3, which is the receiving station for data from
Immediately after completing the reception of data, modem C3
Outputs a transmission request signal RS to. The modem C3 having received the transmission request signal RS similarly detects the presence or absence of a low group carrier on the transmission line D. When transmission line D is empty, modem C3
sends the low group carrier to the transmission path D, and when it receives the high group carrier converted by the frequency converter E, it outputs the send ready signal CS to the CPUA3 via the RS232C interface B3, and the CPUA3 transmits. acquire the right. Then, for the data received from CPUA1 that specified the address of its own station,
Outputs ACK data by specifying the address of the terminal station of CPUA1, and notifies CPUA1 of completion of data reception. Such a procedure enables mutual communication between each terminal station. The communication control means performs such processing, and is executed under program control of the CPUA 1 or the like. In this embodiment, this communication control means is called a communication preprocessor. As shown in the timing chart of FIG. 3, this communication preprocessor is executed in parallel with the application program by time-sharing processing with the application program. The information processing device of one terminal station is configured as shown in FIG. That is, the key code output from the keyboard 2 is sent to the serial/parallel converter 3.
The code is input to the key code buffer 4 via the key code buffer 4. When a keycode is input to keycode buffer 4, CPUA1 inputs the keycode by interrupt processing.
It is input to the key input buffer 61 formed in the RAM 6. The key input buffer 61 has a FIFO configuration. CPUA1 also includes ROM5 and
RAM6 is connected, and RAM6 has an operating system (hereinafter referred to as "OS") including a basic input/output system (hereinafter referred to as "BIOS").
, key input buffer 61, reception buffer 62,
Transmission buffer 63, mode flags 64 to 69 indicating each mode of the terminal station, calling file name storage area 7
0, a read/write address storage area 71, a work file 72, etc. are formed. Further, a disk G1 is connected to the CPUA1 via a disk drive device F1, and a file is formed on the disk G1. FIG. 4 shows the procedure for reading the key code from the key input buffer 61 among the processing steps of the CPUA1.
It shows the processing procedure of BIOS (hereinafter referred to as "KBBIOS"). In the application program, this can be done using the keyboard read command.
KBBIOS is called and executed. step 100
Then, one character of data is read from the key input buffer 61, and in the next step 102, the key code of that one character is stored in a predetermined area. The process then proceeds to step 104, where it is determined whether the called station mode flag 65 is on. Called station mode flag 6
5 is a flag that stores whether or not the own station is designated as a called station. If the determination result in step 104 is NO, the process moves to step 108, where it is determined whether the calling station mode flag 64 is on. This calling station mode flag 64 is a flag for determining whether or not the own station is designated as a calling station. If the judgment result in step 108 is NO,
Proceeding to step 112, it is determined whether or not there is a call command in the reception buffer 62. A paging command is a command sent from a calling station that designates its own station as a called station. If the determination result in step 112 is NO, the process proceeds to step 122, where it is determined whether the key code read from the key input buffer 61 is a communication request code. The communication request code is a code for designating the own station as a calling station, and is, for example, a code output when a predetermined function key on the keyboard 2 is pressed. If the determination result in step 122 is NO, this process is completed and the process returns to the calling application program. Traditional KBBIOS
In this case, there is no determination in steps 104 to 122, and the key code is simply read into a predetermined area. If the key code does not exist in the key input buffer 61, this is used as return information and the calling program to return to. In the above process, if it is determined in step 112 that there is a calling command in the reception buffer 62, the process moves to step 114, where the called station mode flag 65 is set on, and in step 116, the call command is input to the reception buffer 62. Based on the data, calling station name data and calling file name data are stored in a predetermined area of RAM 6, and a read/write mode flag 66 is set depending on whether the file is to be read or written.
The continuation flag 68, which designates continuation of communication, is set on. Next, step 118
Set the ACK data to the transmission buffer 63 with
At step 120, the send flag 67 is set on and the program returns to the calling program. Transmission flag 6
7 is set on, the data set in the transmission buffer 63 by the communication preprocessor is sent to the calling station in the form of a data frame with the address of the calling station added in parallel with the execution of the application program. Sent. Furthermore, if the key code inputted in step 122 is determined to be a communication request code, the process moves to step 124, where the calling station mode flag 64 is set on, and in the next step 126, the destination The called station name data, the calling command, the calling file name data, and the read/write command specifying whether to read or write the file are set in the sending buffer 63, and in the next step 128, the sending flag 67 is set on. be done. When the transmission flag 67 is set on, the communication preprocessor converts the data set in the transmission buffer 63 into a data frame with the address of the called station added in parallel with the execution of the application program. The call is sent to the called station. In this way, after setting whether the local station is a called station or a calling station, and setting various other data such as the calling file name and read/write mode, next
When KBBIOS is called again, the judgments in steps 104 and 108 are executed, and if the local station is in the called station mode, the process moves to step 106 and the fifth step is executed.
When the file access acceptance program shown in the figure is executed and the local station is the calling station, the step
The process moves to 110, and the file access request program shown in FIG. 6 is executed. With the above processing,
Initial settings for sending and receiving file data are completed. (1) When the own station is the called station As described above, the paging command is received from the calling station, and steps 112, 114 to 120 of the KBBIOS execution process are executed.
Through the process described above, the own station is designated as the called station, various data such as a paging file, and the mode are set, and when the preparation as the called station is completed, ACK data is transmitted to the calling station. After that, when the calling station is in file data reading mode, it sends an ACK message indicating that it is ready to receive file data.
Send the data to the called station. At step 200, it is determined whether or not there is ACK data in the reception buffer 62. If there is ACK data, the process moves to step 202 and it is determined whether or not the continuation flag 68 is on. Continuation flag 68
If it is on, it means that communication is to be continued, so the process moves to the next step 204, and the call file input in the call file name storage area 70 is accessed. Next, in step 206, it is determined whether or not a call file exists. If a call file exists, in the next step 208, the state of the read/write mode flag 66 is determined. (a) In the case of file reading If the read mode is determined in step 208, the process moves to step 210, and the stored data is transferred to the transmission buffer 63 from a predetermined address of the calling file. And the next step
In step 212, it is determined whether the transferred data is the data end or not. If it is not the data end, it means that there is next continuous data to be sent, and the step is started.
At step 252, the transfer source file address of the next data is stored in the read/write address storage area 71, and at the next step 254, the continuation flag 68 is set on again. Then, the process moves to step 218, where the transmission data length is set in the transmission buffer 63, and the transmission flag 67 is set on at step 220, and KBBIOS returns to the calling program. Then, in parallel with the execution of the application program, if the transmission flag 67 is on, the communication preprocessor configures the data set in the transmission buffer 63 into a data frame with the calling station address added and transmits it. . When the transmission is completed, the transmission flag 67 is turned off. Then, when the calling station completes receiving the paging file data, it outputs ACK data to the called station. When this KBBIOS is called again from the application program (normally, it is called every time data for one character is read from the key input buffer 61), in step 200, the KBBIOS is called from the calling station.
The reception of ACK data is monitored, and if ACK data has not been received, it is determined in step 222 that the write mode is not present, and the process proceeds to step 224.
Then, it is determined whether the timer set when the communication preprocessor completes data transmission has timed out. If the time has not expired, the program returns to the calling program. If ACK data is received in the reception buffer 62 within the set time in step 200 during subsequent KBBIOS calling, the same process as described above is repeated. That is, the continuation flag 68 is determined to be on in step 202, the calling file is accessed in step 204, and the file data is read from the address of the data stored in the read/write address storage area 71 to be continuously transferred in step 210. A process is executed in which the data is transferred to the transmission buffer 63. In this way, after the file data is transmitted sequentially in parallel while inputting the key data, when it is determined in step 212 that the data to be transferred in the file is at the data end, the process moves to step 214 and the data is transferred. Transmission data with a data end command added to the end of the data is formed in the transmission buffer 63. The continuation flag 68 is then turned off in step 216, the transmission data length is set in step 218, and the transmission flag 67 is set in step 220, thereby transmitting data to the calling station. Then step 200 during subsequent KBBIOS runs
If the reception of the ACK data is confirmed in step 202, it is determined whether the continuation flag 68 is on or not. However, if the transmission of all the data in the calling file is completed, the continuation flag 68 is turned on. Since this is off, the process moves to step 244, where processing is executed to complete the data transmission and reception between the calling station and the called station. That is, in step 244, the called station mode flag 65 is reset to OFF.
In step 246, ACK data is set in the transmission buffer 63, and in step 248, the transmission flag 67 is set on, and the ACK data is transmitted to the calling station, completing the file data read communication. (b) In the case of file writing, the calling station is output from the called station in step 118.
When ACK data is received, write file data is immediately output. If the read/write mode flag 66 is set to the write mode for writing the received data received by the receive buffer 62 to the calling file, the called station immediately writes the received data to the file. Processing is executed. That is, the determination at step 200 is NO, the determination at step 222 is YES, and the reception buffer 62 is cleared at step 223.
If it is determined that there is received data, then in step 230 the received data in the receive buffer 62 is written from a predetermined address in the calling file. Next, step
In step 232, it is determined whether or not the write data is at the data end. If not, in step 238, the next continuous write address of the file is stored in the read/write address storage area 71.
At step 240, the continuation flag 68 is again set on. Then, the process moves to step 236, where ACK data indicating that writing of the received data to the file has been completed is set in the transmission buffer 63, and the transmission flag 67 is set on in step 242. , ACK data is sent to the calling station. The calling station receives this ACK data, and if there is continuous transmission data, it transmits the next write data, and if there is no continuous transmission data, a transmission completion procedure is executed. If it is determined in step 232 that the write data is at the data end, the continuation flag 68 is reset to OFF in step 234, and similarly, in step 236, it is determined that writing of the received data to the file has been completed. The ACK data indicated is set in the transmission buffer 63, and the transmission flag 67 is set on in step 242, thereby transmitting the ACK data to the calling station. When the continuation flag 68 turns off, the subsequent
When KBBIOS is executed, the determination at step 202 is NO, and the reception completion procedure from step 244 described above is executed. In this system, when reading a data file, the calling station sends ACK data to the called station upon receiving data in order to notify the called station of the data receivable state. The called station receives the ACK
The data is checked and the next file data is sent. Conversely, when writing file data,
The called station outputs ACK data to the calling station to notify the calling station that it is ready to receive file data.
The calling station receives the ACK data and sends file data to the called station. Therefore, the called station, in file reading mode,
Even after a certain period of time has passed after data transmission to the calling station is completed,
If ACK data is not received from the calling station,
Processing from step 225 onwards is executed as a time-over error. Also, in write mode,
If file data is not received within a certain period of time after transmitting the ACK data to the calling station, a time-over error is detected and the processes from step 225 onwards are executed. That is, in order to abandon communication with the calling station in step 225, the abort command is sent to the sending buffer 63.
By setting the transmission flag 67 to ON in step 226, an abort command is transmitted to the calling station, and the called station mode flag 65 is set to OFF in step 228, completing the communication procedure. If it is determined in step 206 that there is no call file, the process moves to step 250, and the command with no call file is sent to the sending buffer 6.
3 and the process moves to step 225, where abort processing is executed. Conversely, when an abort command is transmitted from the calling station, the determination in step 201 is YES, and the communication completion process in step 244 and subsequent steps is executed. (2) When the own station is the calling station The steps in the KBBIOS execution process as described above
Through the processes in steps 122 and 124 to 128, the own station is designated as the calling station, and various data such as the calling file name and mode data are sent to the called station by key input, etc., and the calling station receives a calling command, etc. When preparations such as mode setting of the called station are completed, ACK data is transmitted from the called station to the calling station (processing of steps 114 to 120 at the called station). In the calling station, if the calling station mode flag 64 is set to ON, the determination at step 108 will be YES during subsequent execution of KBBIOS, and the process will proceed to step 110, where the file access request program shown in FIG. 6 will be executed. is executed. A call request command is sent to the called station, and when the called station becomes able to communicate, the called station sends ACK data. At step 300, it is determined whether or not there is reception data in the reception buffer 62. If there is reception data, the process moves to steps 301 and 302, and at step 302, it is determined whether or not the call acceptance flag 69 is on. The call acceptance flag 69 is set on upon receiving ACK data transmitted when the called station becomes communicable. That is, initially, the call acceptance flag 69 is reset to OFF, and the
When it is determined that ACK data has been received in step 306, it is set on in step 306 and the step
At 308, a continuation flag 68 indicating continuation of communication is set on. Then, in step 309, the read/write mode flag 66 is checked, and if it is the read mode, the process moves to step 346, where ACK data is set in the transmission buffer 62, and in step 322, the transmission flag 67 is set on. By doing so,
Indicates that file data can be received
The ACK data is sent to the called station, and this KBBIOS returns to the calling program. From then on, the calling station
It becomes possible to receive file data. Further, if the determination in step 309 is NO, that is, in the case of write mode, the process moves to step 330 and subsequent steps, and the first transmission procedure of the file data for writing is executed. Next, when KBBIOS is activated, it is determined in step 300 whether there is any data received in the reception buffer 63. If there is no received data, the step
336, it is determined whether the time is over or not,
If it is not timed out, this KBBIOS returns to the calling program. Further, in the case of time over, the process moves to step 338, and an abort process similar to the procedure shown in FIG. 5 (steps 225 to 228) for the called station is executed. Note that the timer for determining time-over is set by the communication preprocessor when data transmission is completed. If it is determined in step 300 that there is received data in the reception buffer 63, the process moves to steps 301 and 302, and in step 302 it is determined whether or not the call acceptance flag 69 is on. At this time, since communication is possible, the call acceptance flag 69 is on, and the process moves to step 310, where the continuation flag 6 is turned on.
8 is on or not. Since the continuation flag 68 is still on at this time, the process moves to step 312 and the state of the read/write mode flag 66 is determined. (a) For file reading If the read/write mode flag 66 is set to read mode in step 312, the step
Input processing of data sent from the called station of the other party of 314 or less is executed. That is, in step 314, the data stored in receive buffer 62 is transferred to work file 72. Then, in the next step 316, it is determined whether the received data is the data end or not, and if it is not the data end, the step 316 is performed.
318 and work area write address storage area 7
The write address stored in 3 is updated.
Next, in step 320, the ACK data is set in the transmission buffer 63, and in step 322, the transmission flag 67 is set on, so that ACK data indicating that the file data has been successfully received is sent to the called station. Sent. Then, as described above, the called station receives the ACK data from the calling station within a predetermined time, and if the transmission data continues, it transmits the next file data to the calling station. The calling station steps through the received data in the receive buffer 62 every time KBBIOS is called and executed.
If the received data is checked in step 300, the received file data is sequentially transferred to the work file through the steps described above while the continuation flag 68 is on. Then, when it is determined in step 316 that the received file data has a data end,
The process moves to step 344, where the continuation flag 68 is reset to OFF, and the response ACK data is set in the transmission buffer 62 at step 346, and the next step is started.
At 322, the send flag 67 is set on and the ACK is sent.
The data is sent to the called station. After that, when this KBBIOS is called, it will normally receive ACK data from the called station, and if the decision in step 300 is YES, then the call will be made in step 301.
The judgment in step 302 is NO, the judgment in step 302 is YES,
If the determination in step 310 is NO, the process moves to step 324, where the call acceptance flag 69 is reset to OFF, and the calling station mode flag 64 is reset to OFF in step 326, so that the file from the called station is not accepted. The data reading process is completed. (b) In the case of file writing In the case of file writing, when the ACK data sent from the called station in response to the paging command is received, steps 300 to 309 are executed and the judgment in step 309 is If the answer is NO, the process moves to step 330 and the first transmission procedure of the file data for writing is executed. That is, in step 330, the transmission data of the work file 72 and its data length are set in the transmission buffer 63. Then, in the next step 332, it is determined whether the transmitted data is the data end, and if it is not the data end, the process moves to step 334,
The read address of the work area stored in the next work file read address storage area 74 is updated, and the transmission flag 67 is set on in step 322. If it is determined at step 322 that the data has ended, the process moves to step 340, where the continuation flag 68 is reset to OFF, and the process proceeds to the next step 342.
Then, the data end command is set in the transmission buffer 63, and the transmission flag 67 is set on in step 322. Next, when one transmission of file data to the called station is completed, ACK data indicating that the called station is ready to receive the next data is sent to the calling station. If the continuation flag 68 is on, the next time KBBIOS is executed, the determination in step 300 is YES, the determination in step 301 is NO,
The determination in step 302 is YES, the determination in step 310 is YES, the determination in step 312 is NO, and the process moves to step 328. And the reception buffer 62
If ACK data is received from the called station, the process moves to step 330 and the work file 72 is
Next, the transmission data and its data length are set in the transmission buffer 63. And the next step
In step 332, it is determined whether the transmitted data is the data end or not. If it is not the data end, step 334 is performed.
At step 322, the read address of the next work area is updated, and the transmission flag 67 is set on. If it is determined at step 322 that the data has ended, the process moves to step 340, where the continuation flag 68 is reset to OFF, and the process proceeds to the next step 342.
Then, the data end command is set in the transmission buffer 63, and the transmission flag 67 is set on in step 322. Furthermore, if ACK data has not been received in step 328, it is determined in step 336 whether or not the time has expired.
Return to the calling program of KBBIOS. Also,
If a timeover occurs, step 338
Then, the abort processing similar to that shown in steps 225 to 228 in FIG. 5 is executed. Furthermore, if it is determined in step 322 that the file data to be transmitted is the data end, the continuation flag 68 is turned off in step 340, so the next time KBBIOS is executed, the determination in step 310 will be NO. Then, the process advances to step 324, where the call acceptance flag 69 is reset to off, and at step 326, the calling station mode flag 64 is reset to off, completing the data transmission procedure. Note that when an abort command is received from the called station, the determination at step 301 becomes YES, and the processes from step 324 onwards are executed, completing the data transmission procedure.

【Effect of the invention】

As described above, the computer communication system of the present invention connects a computer to a coaxial transmission line connected to a frequency converter via a modem, etc., and uses interrupt processing to communicate between the transmitting and receiving buffers of each terminal station in the computer. a communication control means for transmitting and receiving data as a background job;
In the process of reading key code data input from the keyboard, it determines the presence or absence of received data in the send/receive buffer, accesses the data file according to the received data, and exchanges data between the send/receive buffer and the data file. Since the key input control means is provided, when the computer of one terminal station is executing key data input processing, the file of that computer is inputted in parallel with the data input processing. , it becomes possible to access it from computers at other terminal stations. Therefore, the workability of file access between terminal stations is improved, and the data file held in any one terminal station can be used effectively between each terminal station, resulting in effective use of data files. is planned.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a computer communication system according to a specific embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of one terminal station in the system. FIG. 3 is a timing chart showing the execution relationship between an application program executed on a computer of one terminal station and a communication preprocessor. FIG. 4, FIG. 5, and FIG. 6 are flowcharts showing the processing procedure of the CPU of each terminal station.

Claims (1)

[Scope of Claims] 1. A computer having an external storage device in which a data file is formed, a keyboard for inputting data, a transmitting/receiving buffer for inputting data transmitted and received between a central processing unit and a terminal station, and output data of the computer. a terminal station comprising a serial interface that converts the serial signal into a serial signal, and a modem that modulates and demodulates the serial signal and the analog signal; a coaxial transmission line to which the modems of the plurality of terminal stations are connected; a frequency converter connected to a transmission line and converting a transmission frequency band outputted from the terminal station into a reception frequency band; a communication control means for transmitting and receiving data as a ground job; and the computer determines whether or not there is received data in the transmitting/receiving buffer in the process of reading key code data input from the keyboard, and transmits data according to the received data. A computer communication system comprising: key input control means for accessing the data file and exchanging data between the transmission/reception buffer and the data file.