IE71661B1 - Automatic program conversion for video terminal compatibility - Google Patents

Description

Automatic Program Conversion for Video Terminal Compatibility The invention relates to automatic program conversion for video terminal compatibility.

At present, in many situations a computer system having a video terminal runs under the control of a program having commands which are compatible with that category of video terminal only. While such a situation is satisfactory if the programs are not required to be transferred onto a target computer system having different video terminals, considerable difficulties arise if this is not the case. For some programs, many months of man-hours are required for printing all source code lines, analysing all of the lines, re-writing the commands for a specific type of video terminal and inserting replacement commands. In addition, in some cases connection of additional or replacement video control circuits to the target system is necessary.

Another approach to achieving compatibility is described in the specification of British Patent No. 2,205,219 B (Hercules Computer Technology). This describes a computer system having 71661 - 2 dedicated colour/display controllers connected to a raster memory and to the CPU for automatically and on-line converting display commands to a format which is suitable for the particular type of video terminal. A problem with this approach is that quite an amount of communication between the various circuits and memories is required and processing delays are likely to incur where the screen displays must be changed quite frequently.

The invention is directed towards providing a method and apparatus for automatic program conversion for video terminal compatibility which 10 eliminates the above-mentioned problems.

According to the invention, there is provided a process for enabling a first computer system having one category of video terminal to operate compatibly under the control of a computer program written for compatibility with a second computer system having a different category of video terminal to that of the first computer system, the process being carried out by a central processing unit in an apparatus also comprising a storage device and a memory circuit, the process performing automatic conversion of said computer program by performing the steps of:transferring a program from the storage device to the memory circuit; writing a common statement in a header of the program, the common statement comprising a series of names of pixel control instructions, each instruction being associated with a target screen physical region and a - 3 display category of said first computer system and wherein there is at least one display category associated with each physical region; analysing each line of the program in turn, and for each line;· detecting a target screen cursor positioning command, if one exists in the line; determining a display category associated with data of the cursor positioning command by reference to pre-stored lexicons; using the display category, selecting a colour statement for referring a program pointer to one of the instruction names in the header; and writing the selected colour statement into the line in addition to an existing 10 monochrome command; after all lines of the program have been processed, writing target screen pixel control commands in the header; and compiling said commands to generate machine code for use on a target computer system; and the process further comprising the step of. operating said first computer system under the control of said generated machine code.

Preferably, the process comprises the additional step of automatically generating a query signal if there is an unrecognised command in a line which is analysed, and printing the query signal.

The invention will be more clearly understood from the following description of some preferred embodiments thereof, given by way of - 4 example only with reference to the accompanying drawing which is a flow chart illustrating an automatic program conversion process of the invention.

Referring to the drawing, there is illustrated a process 1 for automatic program conversion to ensure video terminal compatibility. The process 1 is illustrated for a number of computer programs and is carried out by an apparatus having a central processing unit and a memory circuit. In step 2 of the process a program is transferred from a disk into the memory circuit of the apparatus. In step 3, the CPU of the apparatus inserts a common statement in the header of the program. The common statement is a series of names of instruction for pixel control at a number of different physical regions on a target video terminal screen. In this example there are three regions on the screen, namely pixels assigned to character line 1, lines 2 to 22, and line 23. In addition, for each region there may be more than one display category. In this embodiment the pixels of lines 2 to 22 may be controlled to display one of two types of data and thus there are two display categories. Thus, the common statement which is inserted into the program in step 3 includes names for pixel control instructions for four display categories associated with three sets of pixels or display regions of a video terminal screen.

In step 4 of the process the CPU of the apparatus analyses the first line of the program which has been loaded into the memory circuit. In particular, the analysis involves detecting a cursor positioning command, which command would normally Include co-ordinates for cursor positioning in a character line a target video terminal screen. If no such command is detected, as represented by step 6 a decision is made as to whether or not there is a command on the line which is not recognised by the CPU. If there are no unrecognised commands, step 4 is repeated for the next line of the program. If there is no other line, step 2 is repeated for the next program, as indicated by the decision step 9. If, however, there is an unrecognised command, in step 7 the CPU of the apparatus generates a query signal which includes the line number in the program and the specific query and this is used for printing a query list in step 8.

If a cursor positioning command is detected in the line, in step 10 the CPU determines the display category associated with the command. The display category may, for example, be a screen header, an error message, a piece of static text or a data field, and is determined by reference to pre-stored lexicons. Using the terminal display category, in step 11 the CPU selects a colour statement for insertion in the line, which colour statement refers the program pointer to one of the four instruction names in the common statement at the header of the program. For example, if the display category is an error message, the instruction name for the display category in the third screen location of line 23 is referred to by the colour statement. If the display category is for a piece of static text, the relevant location is in lines 2 to of the screen and one of the two instruction names associated with this region is selected because it is static text. If on the other hand the category is for a data field prompt, there is a different associated instruction name associated with the second screen region and this instruction name in the common statement is referred to. In this example, the instruction names are simply A, B, C and D.

As indicated by the decision step 12, steps 4 to 11 are repeated for the next line of the program which has been loaded in step 2. When these steps have been carried out for all lines, in step 13 the CPU inserts commands for each instruction name of the common statement. These commands instruct the processor of a target system in which the program will run to control screen pixels to display the relevant data in a certain colour.

Steps 2 to 13 inclusive are repeated for each program. When there is no further program all of the source code which has been converted is compiled to generate machine code for use on a target computer system.

It will be appreciated that the process of the operation operates automatically to convert a program so that it may be used on a particular computer system. In addition, because of the manner in which the common statement commands are inserted at the end of the process, it will be relatively easy for a program to be changed for display of different colours in the various screen locations by simply changing the commands associated with the instruction names. Another important aspect of the invention is that the colour statements which are inserted in step 11 do not replace monochrome commands as they are merely inserted in addition to these commands. The processor of the target system will select either the monochrome command or the colour statement, depending on the type of terminal which is being used. Thus, the process of the invention converts a program so that it may be used on either monochrome or colour target video screens, and in addition the colours may be selected for the different screen locations relatively easily.

The process of the invention eliminates both on-line processing delays associated with conversion of commands and also eliminates many man-hours in conversion of a program.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Claims (4)

1. A process for enabling a first computer system having one category of video terminal to operate compatibly under the control of a computer program written for compatibility with a second computer system having a different category of video terminal to that of the first computer system, the process being carried out by a central processing unit in an apparatus also comprising a storage device and a memory circuit, the process performing automatic conversion of said computer program by performing the steps of:transferring a program from the storage device to the memory circuit; writing a common statement in a header of the program, the common statement comprising a series of names of pixel control instructions, each instruction being associated with a target screen physical region and a display category of said first computer system and wherein there is at least one display category associated with each physical region; analysing each line of the program in turn, and for each line:detecting a target screen cursor positioning command, if one exists in the line; determining a display category associated with data of the cursor positioning command by reference to pre-stored lexicons; -lousing the display category, selecting a colour statement for referring a program pointer to one of the instruction names in the header; and writing the selected colour statement into the line in addition to an ’ existing monochrome command; after all lines of the program have been processed, writing target screen pixel control commands in the header; and compiling said commands to generate machine code for use on a target computer system; and the process further comprising the step of: 10 operating said first computer system under the control of said generated machine code.

2. A process as claimed in claim 1 comprising the further step of generating a query signal for a program line if no cursor positioning command is detected in the line and if there is an unrecognised command 15 in the line.

3. A process as claimed in claims 1 or 2, wherein lines of a plurality of programs are processed before the commands are compiled.

4. A process substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.