JPH0461373B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to an electronic computer (hereinafter abbreviated as computer).
The present invention relates to a data reading method in a data processing device.

(b) Background of the technology In recent years, rational design of programs has been actively carried out, but in order to realize this, it is desirable that only the display required by the operator appears on the computer display screen or printer surface. Various efforts have been made.

FIG. 1 shows the main part of a data processing device in a computer, and a file 4 stores data having various record lengths. The data processing section 6 on which the user program 3 runs exchanges commands with the data management section 5, while the data management section 5 exchanges commands with the file 4.

(c) Prior Art and Problems Now, when a read command for reading data stored in the file 4 is transmitted from the data processing unit 6 to the data management unit 5 as shown by arrow A,
Data is read out from the file 4 to the buffer 2 in the central processing unit (Cpu) 1 as shown by arrow B. And this buffer 2 is data management section 5
The data in the buffer 2 is read into the user program 3 as shown by arrow C.

Here, it is assumed that the minimum unit of data is, for example, 8 bits, and this is called one record. and,
For example, for the convenience of understanding, multiple records are
It's called a block.

The processing unit of the file 4 described above is large, ie, one block, but the processing unit of the user program 3 is small, and is limited to only one record. For this reason, one block of data read into the buffer 2 from the file 4 cannot be read into the user program 3 as is. For this purpose, an operation called blocking/deblocking is normally performed, and the user program 3 reads out one block of data stored in the buffer 2, which is made up of the above-mentioned plural records, by breaking it down one record at a time. It is a common practice to carry out predetermined calculations in the calculation section 7.

However, from the user program 3's point of view, unless it knows how many records a unit block (one block) consists of, it cannot judge how far into the data read into the buffer 2 it should read. For this purpose, conventionally, a method has been adopted in which a unit block is defined in the file 4 by forming a predetermined n number of records.
For convenience of explanation, one block will be explained below as being made up of, for example, three records. Therefore, in this case, in order for the user program 3 to read one block stored in the buffer 2, it is only necessary to read the data three times.

If the data length is defined as one record in this way, there is no problem. However, in reality, some data that must be processed can be stored in one record, such as an employee number, or several records, such as an address, depending on the target person. There are some things that take a long time.

In this way, as shown in Figure 2a, there is data that requires a length of 1 for one record, and as shown in Figure 2b, there is data that requires a length of 2 for two records, or as shown in Figure 2b. 3 as depicted in figure c.
Since there is data with a record length of 3, if data with various record lengths is stored from file 4 into buffer 2, user program 3 will not be able to handle the situation when one read command is transmitted to file 4. In this case, when looking at buffer 2 from user program 3, the data in buffer 2 is one block, but it is not clear how many records it corresponds to. This inevitably causes the inconvenience that the user program 3 has no idea how many times it will have to read the information in the buffer 2 to finish reading one block.

Moreover, once the reading of the first one block written earlier is completed, the second one block is subsequently written into the buffer 2. is the second 1
If it is longer than the block, user program 3
does not have a function to judge where to stop reading, so when reading, following reading of this second block, the first block that was written last time is read. A scandal occurs in which the data at the end of the file is read out. If this happens, if the program appears on a display screen (not shown),
After the program corresponding to the second block, the remainder of the previous program corresponding to the first block will be displayed, resulting in an uncomfortable situation.

(d) Purpose of the Invention The present invention has been made in view of the above-mentioned drawbacks of the conventional technology, and is based on the continuous data input from file 4 to buffer 2 without separating the information in buffer 2 for each record. It is an object of the present invention to provide a simple data reading method that can easily identify how far to read, thereby eliminating the above-mentioned inconvenience.

(e) Structure of the Invention According to the present invention, the object is to read the data read out in blocks from the file 4 based on the control of the data management section 5 in units of records so that the data processing section 6 can read the data in units of records. In a data processing device provided with a buffer 2 determined by the data management unit 5 between the data processing unit 6 and the data processing unit 6,
Each time a read command is issued from the data processing section 6, a specific code is temporarily stored in the entire data storage area of the buffer 2, and then the data read out in blocks from the file 4 is stored at a predetermined position in the buffer 2. The data reading method is characterized in that the specific code is written in a rewritten manner, and when the specific code appears when reading data from the buffer 2 to the data processing unit 6 in record units, the data reading is terminated. achieved.

(f) Embodiments of the Invention The data reading method according to the present invention will be described in detail below with reference to the drawings.

3a to 3b show the procedure for writing data into the buffer 2 using the data reading method according to the present invention. First, as shown in Figure 3a, the entire surface of the buffer 2 is filled up by storing codes that are rarely found among the various codes handled by this data processing device, such as a specific code called FF. . Then, as shown in FIG. 3b, starting from a predetermined position of the buffer 2, for example, point p in FIG. Store the records in order by rewriting them. By doing this, when reading record units from buffer 2,
Since the record FF appears immediately, it is clear that reading of one block of data has been completed.

All of the data stored here is read by the user program 3, but when the second block of data is subsequently stored from the file 4 to the buffer 2, a read command is issued as described above. It is transmitted as shown by arrow A. At the same time as this read command is issued, the entire buffer 2 is again filled with FF codes as shown in FIG. 3c.
That is, this operation erases all the previously written data for the first block. After doing this, the data of the second block is also transferred from the same point p in file 2 as shown in Fig. 3 d.
Write in the direction of the arrow H as shown.

In this way, the reading end point of the second block becomes point Q.

For this reason, even after reading the data of the second block, which has a shorter data length than the first block, ends at point Q, an FF code will immediately appear even if a strong subsequent read operation is attempted. In this case, the reading should be stopped immediately if the FF code appears.

If you do this, as mentioned above, even if the data of the second block written this time is displayed on the display screen (not shown) of the computer, the second half of the data of the first block written last time will be displayed immediately after it. (Remaining portion) can be prevented from being displayed at the same time.

(g) Effects of the Invention As explained in detail above, if the data reading method of the present invention is used, only the display required by the operator will appear on the display screen used in a computer or on the printer surface, making it practical. Great effects can be expected.

[Brief explanation of drawings]

Figure 1 is a diagram showing the main parts of a data processing device in a computer, Figures 2 a to c are diagrams showing record lengths of various data read during buffering, and Figure 3
The figure is a diagram showing a data reading method of the present invention. In the figure, 1 is a central processing unit, 2 is a buffer, 3 is a user program, 4 is a file, 5 is a data management section, 6 is a data processing section, and 7 is a calculation section.

Claims (1)

[Claims] 1. Based on the control of the data management section 5, the file 4
In a data processing apparatus, a buffer 2 determined by a data management section 5 is provided between a file 4 and a data processing section 6 so that the data processing section 6 can read data read out in blocks from a record in units of records. Each time a read command is issued from the data processing unit 6, a specific code is temporarily stored in the entire data storage area of the buffer 2, and then the data read out in blocks from the file 4 is stored at a predetermined position in the buffer 2. A data reading method characterized in that the specific code is written in a rewritten manner, and when the specific code appears when reading data from the buffer 2 to the data processing unit 6 in units of records, the data reading is terminated.