JPH0784800A - Character font emulator and computer system - Google Patents

Abstract

PURPOSE:To construct a character font emulator and a computer system capable of operating an OS prepared for the computer system provided with a character font ROM and an application program operated on the OS on the computer system not provided with the character font ROM. CONSTITUTION:A CPU 11 secures a window area 23 for emulating a font ROM window and an area 24 for storing the font of the same contents as the font ROM on a main memory 12, selects the font by selecting a command, loads the character font to be used through the window area in a secured RAM area, permits the reference of the character font mapped on the RAM area through a memory controller 14 and performs an operation for data protection for prohibiting write.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to a character font ROM.
Character font R on computer systems without
The present invention relates to a character font emulator capable of operating an application program created on the assumption that OM exists.

[0002]

2. Description of the Related Art In the field of personal computers, both hardware and software have been substantially standardized to make effective use of software assets. In a personal computer that handles character fonts, the character fonts are stored in ROM, and therefore the OS (operating system) has also been created on the premise of the font ROM.

In particular, many OSs dealing with Japanese are created on the assumption that a double-byte character (kanji) font is included in the ROM, and this is operated as it is on a computer without a kanji font ROM. I can't.

On the other hand, there is a Japanese OS that operates on a computer that does not have a Kanji font ROM, but many application programs do not operate as they are because of different font access methods. Therefore, they are changed or newly created. It was a wasteful investment that had to be made.

[0005]

As described above, the conventional computer system including a personal computer has a font ROM for an OS created on the basis of a Kanji font ROM and an application program operating on the OS. Could not be run on no computer system. Further, when a new OS is created for a computer that does not have a ROM, application assets accumulated in the past cannot be used, and useless development investment is required.

The present invention has been made in view of the above circumstances, and an OS created for a computer system having a character font ROM and an application program operating on the OS are computer systems having no character font ROM. An object of the present invention is to provide a character font emulator which can be operated on the above and a computer system including the character font emulator.

[0007]

SUMMARY OF THE INVENTION The present invention is a computer system for operating an operating system operating on a computer system having a character font in a ROM on a computer system having no character font ROM, which is on a memory. Means for memory mapping that allocates a part of the RAM area to the portion corresponding to the font ROM area, means for a trap that permits access to the RAM area, and RAM area where the character font to be used is mapped. And a character font emulator comprising means for loading transfer. The character font emulator has a window area for emulating a font ROM window and a RAM area for securing a RAM area for storing a font having the same contents as the font ROM, and font selection by command selection. A step for selecting and transferring a font for loading a character font used through the window area into the RAM area secured as described above;
A step for data protection which permits the reference of the character font mapped in the RAM area and prohibits the writing. Further, as hardware, a trap control device for determining a character font to be transferred by command selection, mapping an appropriate character font to the window and permitting access, and a paging mechanism for accessing the character font via a window. And a memory control device having.

[0008]

According to the present invention, a control mechanism (paging) for window access for mapping and accessing a RAM area in a portion in a font ROM area on a memory,
A font ROM emulation is realized by a trap mechanism that monitors access to the memory and a font loader that loads a character font into a mapped RAM area. The character font emulator is a window area that emulates a font ROM window,
Also, an area for storing a font having the same contents as the font ROM is secured, the font is selected by command selection, the character font used through the window area is loaded into the RAM area secured as described above, and the RAM Allows reference to the character fonts mapped in the area and prohibits writing. Operates for data protection.

As a result, the OS premised on the font ROM and the application operating on the OS can be operated without providing a special font ROM in the computer, and the existing application assets can be inherited. Further, it is not necessary to provide a new OS, and there is an effect that a unified operating environment can be realized without being affected by the difference in OS depending on the presence or absence of the font ROM.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, reference numeral 11 is a CPU, which serves as a control center for emulation of the present invention, and OS and application programs stored in RAM (main memory 12) and BIOS (basic input / output control system) stored in ROM 13. Run the program. Figure 3,
The program for emulation shown by the flowchart in FIG. 4 is also executed. The flowcharts shown in FIGS. 3 and 4 exist as a part of the BIOS program stored in the ROM 13.

Reference numeral 12 is a RAM, which is also used as a work area in addition to the programs described above, for example, as a font ROM window area described later. Reference numeral 13 is a BIOS-ROM.

Reference numeral 14 is a memory control unit (MCU). The memory control device 14 has a page control register built therein, and by paging controlling the RAM 12, the externally connected expansion memory 17 can be accessed at high speed through a window. Since this mechanism is conventionally known as paging or EMS, detailed description thereof is omitted here.

Reference numeral 15 is an input / output control unit (IOC). The input / output control device 15 is functionally divided into an IO trap control unit and a data transfer control unit. Reference numeral 16 is an output device, for example, a display device such as a CRT or a flat panel. Reference numeral 17 is a relatively large capacity expansion memory, which is optionally installed in an expansion slot of the system. Reference numeral 18 is a system bus, and the blocks 11 to 17 described above are commonly connected.

FIGS. 2 to 4 are respectively cited for explaining the operation of the embodiment of the present invention, and FIG. 2 shows the operation on a memory map ((a) is conventional, (b) is FIG. (Embodiment of the present invention), FIG. 3 is a flowchart showing the conventional initialization processing of the emulator, and FIG. 4 is a flowchart showing the trap processing.

In FIG. 2, (a) is a conventional example and (b) is a conventional example.
FIG. 7 is a diagram showing the operation of the embodiment of the present invention expanded on the main memory 12. Reference numeral 21 is a font ROM window,
The CPU 11 accesses the character font via this area.

Reference numeral 22 is a font ROM, and conventionally a character font is stored in this ROM. Since a normal font requires a relatively large capacity, it is accessed through the font ROM window 21.

Reference numeral 23 is an emulated font R
The OM window is an area mapped to the RAM area 24 in which fonts are stored. Reference numeral 24 is a character font storage area in which the same font as the content stored in the font ROM 21 is loaded from the expansion memory 17 and stored.

3 and 4 are flowcharts showing the operation of the embodiment of the present invention. FIG. 3 shows the initialization processing of the emulator and FIG. 4 shows the trap processing. In the figure, reference numeral 31 is a step for securing the font ROM window, and an area for emulating the font ROM window is secured in the main memory 12. Reference numeral 32 is a step for similarly securing a font RAM area in the main memory 12, and under the control of the CPU 11, the font ROM
An area is reserved for storing a font having the same contents as. Reference numeral 33 is a step of loading a character font from the expansion memory 17, and loads a font having the same contents as the font ROM into the area secured in step 32 described above. This loading is controlled by the input / output control device 15 under the control of the CPU 11. Reference numeral 34 is a step for enabling the font selection command to be trapped.
Set traps or memory read / write traps.

Reference numeral 41 is a step of determining a font to be selected, and the font is determined from the information of the I / O trap or the memory read / write. Reference numeral 42 is the font RO shown in FIG. 2 for the font determined in step 41.
This is a step of mapping to the M window 23, and the character font is permitted to be accessed via the font ROM window 23 here.

The operation of the embodiment of the present invention shown in FIG. 1 will be described below with reference to FIGS. In the embodiment of the present invention,
It is assumed that the area for storing the font exists in the area accessible from the CPU 11 and the system has a sufficient memory capacity for storing the font. It is also assumed that the CPU 11 has a memory management function such as a paging mechanism and an I / O trap processing function.

FIG. 2A shows a memory space of a conventional computer system having a font ROM. Generally, a font requires a large memory size, so that the entire area is not accessible at one time, and the font is accessed while selecting the required font through the font ROM window 21. You can select fonts via I / O port,
Alternatively, there is a method of using read / write to the memory.

FIG. 2 (b) shows the memory space of the emulated computer system of the present invention. An area corresponding to the font ROM window 21 is mapped to an appropriate RAM area 23. Here, under the control of the CPU 11, a function of correctly selecting an appropriate font via the input / output control device 15 and a function of inhibiting writing to the font storage area 24 via the memory control device 14 are realized.

FIG. 3 shows the flow of processing when the emulator is initialized. The CPU 11 first secures the font ROM window 23 to be emulated. Next, reserve an area to actually store the font and load the required font in that location. Font ROM window 23
The mapping between the font area 24 and the font area 24
Use the memory management function such as paging mechanism.
Finally, enable the ability to trap font selection commands and exit.

FIG. 4 shows the flow of a trap routine for trapping a font selection command. The font to be selected is determined from commands such as input / output processing and memory read / write, and the appropriate font is used as font R.
Map to OM Find 23. Here, CP
Under the control of U11, the I / O trap mechanism and paging mechanism by the input / output controller 15 are used. Through the series of processes, the OS and the application can operate as if the font ROM actually exists.

[0025]

As described above, according to the present invention, the effects listed below can be obtained. (1) It is possible to operate an OS and an application program that operates on the OS assuming the existence of the font ROM, without providing the computer with a special font ROM. (2) Can maintain existing application assets,
Eliminates development investment. (3) It is not necessary to provide a new OS. (4) A unified operating environment can be realized without affecting the difference in OS due to the presence or absence of a font ROM.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration according to an embodiment of the present invention.

FIG. 2 is a diagram showing the operation of the above embodiment developed on a memory in comparison with a conventional example.

FIG. 3 is a flowchart showing an initialization processing operation procedure of the emulator in the above embodiment.

FIG. 4 is a flowchart showing a trap routine in the above embodiment.

[Explanation of symbols]

11 ... CPU, 12 ... Main memory (RAM), 13 ... BIO
S-ROM, 14 ... Memory control unit (MCU), 15 ...
Input / output control device (IOC), 16 ... Output device, 17 ... Extended memory, 18 ... System bus.

Claims (3)

[Claims] 1. An operating system operating on a computer system having a character font in a ROM,
In a system that operates on a computer system that does not have a character font ROM, the font R on the memory
Means for memory mapping for allocating a part of the RAM area to a portion corresponding to the OM area, trap means for permitting access to the RAM area, and loading for transferring a character font to be used to the mapped RAM area. A character font emulator comprising means. 2. A RAM for securing a window area for emulating a font ROM window and an area for storing a font having the same contents as the font ROM.
Processing means for securing an area, font selection by command selection, loading means for loading character fonts to be used through the window area in the RAM area secured by the above, processing means for font transfer and transfer, and RAM area 2. The character font emulator according to claim 1, further comprising: a processing unit for protecting data, which permits the reference of the character font mapped to the above and prohibits writing. 3. A trap control device for determining a character font to be transferred by command selection and mapping an appropriate character font in the window to permit access.
2. A computer system having a character font emulator according to claim 1, further comprising a memory controller having a paging mechanism for accessing the character font via a window.