# Patent

## Title
Method and apparatus for reducing flicker when displaying HTML images on

## Abstract

A method for operating a computer converts a word processing file to a computer program source file, which generates an output stream when run. The word processing file includes a linear sequence of characters having segments marked by beginning and ending tags. The method of the present invention translates the linear sequences of characters in the word processor file that are not surrounded by the tags to output statements in the computer program source file. The output statements cause the computer program generated from the source file, when executed, to reproduce the linear sequences of characters from the word processor file not surrounded by the tags in an output stream generated by the computer program. The method translates the linear sequences of characters in the word processing file that are surrounded by predetermined tags into computer source code statements. In so doing, the translation takes the form of merely copying the linear sequences of characters of the word processing file to the computer program source file or of translating the linear sequences of characters of the word processing file into statements recognized in the computer language.

## Background
The present invention relates to compilers for use in computing systems, and more particularly, to a pre-processor for generating a source file for a predetermined computer language compiler or interpreter in which the resulting computer program generates a word processing file that has part of its content generated by the computer program.

The World Wide Web ("Web") has become a very successful means of communication between central sites connected to the Internet and individual users on the Internet who wish to communicate with the site. The communications are controlled by two programs, a Web Browser that runs on the user's computer and a Web server that runs on the site's computer. A Web Browser sends a request to a Web Server using the HTTP protocol. A request results in a MIME ("Multipurpose Internet Mail Extensions"--see IETF RFC1341, 1342, 1521) Stream being sent back to the Web Browser. The MIME stream includes a Content Type header for the data that indicates how the Web Browser will treat the data being sent. For example, a "text/html" MIME type indicates that the data is in the hypertext markup language (HTML), and should be interpreted accordingly; an "image/gif" MIME type indicates that the data is a "gif" image file, and should be rendered as an image after unpacking the data in the file.

The Web Server typically services a request either by sending back a file stored locally on the server or by running a program, the output of which is the MIME stream to be sent back to the browser. As noted above, the Web typically makes use of the hypertext format to display information to a user and receive input from the user. Hypertext allows a body of information to be organized into a hierarchical system in which the user can pursue increasing levels of specificity by following the various hypertext links from one document to the next. A typical hypertext text display system (a Web Browser) displays a document in which selected words or phrases are highlighted. The highlighted phrase indicates that another document related to that phrase is in the system. If the person viewing the document selects one of these words or phrases by pointing and clicking using a pointing device, the second document related to that word or phrase is sent to the user's screen. The user may return to the original document at any time selecting a "back" option on the viewer screen.

This form of information display has found wide acceptance on the Internet because of its ease of use. A user located at a terminal on the network connects to a server on the network that has a "home page" in hypertext format. The home page is then displayed on the user's screen by the browser. When the user selects a highlighted word, the browser communicates the user's choice to the server in a MIME data stream. The server then transfers the corresponding file to the user's machine via the network. The browser on the user's machine then displays this file to the user.

Conventional browser's also allow the user to input text on the user's screen which is then transferred to the server when the user selects a graphical element such as a "button". Hence, the user can communicate information to the server beyond the predefined hypertext link information, provided the server is programmed to use this information.

The hypertext mode of information organization is also efficient from the point of view of the home page provider on the server. A home page is written in HTML. HTML is a word processing format which allows the user to define a page as the user would with a conventional word processor. In fact, programs for converting the various conventional word processing formats to HTML are commercially available. For each phrase that is to provide a link, the user marks the phrase by enclosing it with beginning and ending "tags". The user then defines another hypertext file that contains the document to be displayed in response to the user selecting the phrase. Hence, a server program can be as simple as a set of HTML documents created with a conventional word processing system and stored on the server.

If the interaction between the user and server is basically a transfer of predefined information which is static in nature, the simple "set of documents" mode is satisfactory. If, however, the information to be transferred requires some form of processing prior to the transfer, the simple hypertext engines are less than ideal. Consider an application in which the server must execute a program to gather and calculate the data that forms a portion of hypertext material that is to be returned to the user. To provide such a service, the server must include a program that is specific to the application and which performs the computations and then generates the results in the form of a hypertext document that is delivered on the network. The HTTP Protocol defines a general mechanism for programs to operate in this way, called the Common Gateway Interface (or CGI). A program that uses this mechanism is often referred to as a CGI Program.

There is no standardized program support for generating hypertext documents within a conventional processing program written in one of the common programming languages such as COBOL or C. The output facilities of these languages typically provide various forms of output statements that allow the program to output a block of text. Hence, to generate the hypertext document, the programmer must, in effect, include statements to writeout the hypertext portion of the document one line at a time. In addition, the user must be familiar with all of the various "tags" used in HTML so that the user can provide these tags in the output stream of the program.

Similarly, the hypertext generating programs provide, at most, a limited scripting capability to support computations on the server. For example, some engines have the ability to make calls to database engines to retrieve data to be inserted into the hypertext document.

Broadly, it is the object of the present invention to provide a system that combines the strength of both a word processor and a conventional computer language.

It is a further object of the present invention to provide a compiler that allows hypertext documents and native computer code to be combined in a manner in which the benefits of compiled general purpose computer language can be achieved in a hypertext document.

These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.

The present invention is a method for operating a computer to convert a word processing file to a computer program that will generate a word processing file when run. The word processing file includes a linear sequence of characters having segments marked by beginning and ending tags. The word processing file is converted to a source file for a computer language. The method of the present invention translates the linear sequences of characters in the word processor file that are not surrounded by the tags to output statements in the computer code source file. The output statements cause a computer program generated from the source file to reproduce the material in an output stream generated by the computer program. The method translates the linear sequences of the word processing file that are surrounded by predetermined tags into computer source code statements. The translation may take the form of merely copying the material to the source file or of translating the statements into statements recognized in the computer language.

FIG. 1 is a flow chart for a preprocessor according to the present invention.

The present invention may be more easily understood with reference to the structure of a typical prior art hypertext document. Such a document consists of a string of characters in which specific sequences of characters are tagged. For the purposes of this discussion, the tagged sequences can be viewed as consisting of two types, those related to on-screen formatting of the document and those related to defining links to other documents. The first type includes tags that mark the beginning and end of sequences to be displayed in a particular style which defines font, print size, etc. Since such formatting is only indirectly related to the present invention, it will not be discussed in detail here.

The second type defines the links to other files. These sequences are defined by placing predefined tags at the beginning and end of each sequence, and specifying the file to sent in response to a user selecting the sequence with the user's pointing device. As these tags are also well known in the computer arts, they will not be discussed further here.

A hypertext document according to the present invention may be viewed as a standard HTML file having a new class of tags. These new tags mark the beginning and end of code sequences in a conventional computer language such as COBOL. The modified document is then used as input to a pre-processor for the computer language compiler in question. The pre-processor converts all conventional hypertext material to output statements in the language in question. This conversion converts the hypertext to the underlying computer language. The converted file is then compiled in the conventional manner to generate an executable that is run on the server in response to a request for the hypertext file. This executable provides the MIME stream when the user requests the hypertext file.

The present invention utilizes pre-processing and compilation to avoid the need to parse the HTML file each time a request is made for the file. The alternative approach of reading the HTML file each time it is needed, interpreting the underlying computer language and replacing data variables places a significant computational load on the server.

The method of the present invention does not restrict either the HTML or computer language portion of the program. The computer language compiler processes the computer language statements, and the HTML browser processes the HTML statements.

The method of the present invention places no restrictions on the user's browser. The user's browser only needs to deal with standard HTML. There is no need to download a specific script language to the user's computer, and hence, the user's browser does not need to be customized for a specific scripting language.

To simplify the following discussion, the underlying computer language will be assumed to be COBOL; however, it will be apparent to those skilled in the art that the teachings of the present invention can be applied with a wide range of conventional computer languages.

In the preferred embodiment of the present invention, a COBOLTYPE tag is added to the HTML language tag set. This tag is optional, but if present, must be in the HTML stream, and must appear before any other HTML or COBOL tags. The COBOLTYPE tag identifies the MIME Content-Type of the output for this program. The full syntax for the COBOLTYPE tag is as follows:

The CONTENT-TYPE parameter indicates the MIME type of the information to be output by the program in the correct format for a CGI Program. If this parameter is not specified, the content type will be "text/html". If the programmer wishes to prevent a content type being output (e.g., the program is not the first in a sequence of COBOL programs or the programmer has some special requirement) then the programmer can use the CONTENT-TYPE="" to ensure that no content type header is output.

The COBOL TAG may embedded anywhere in the HTML stream. The text following the <COBOL> tag is assumed to be COBOL source code until a </COBOL> tag is encountered. For convenience a comment tag <|--COBOL statements--> is also included to allow COBOL statements to be inserted.

In the preferred embodiment of the present invention, an <ITERATE> tag is also included. The <ITERATE> tag marks the beginning of an iteration over a table of variable values. The full syntax for the tag is <ITERATE OVER! variableName>. The number of iterations is the number of the "Occurs" parameter specified for variableName. The iteration continues until a </ITERATE>. Tag is found.

In the preferred embodiment of the present invention, there is also a variable replacement tag having the form <%name%> or alternatively %%name%%. The variable called "name" is substituted for this tag wherever the tag is found. The replacement occurs everywhere in the document, outside the COBOL tagged portion. The replacement does not take place within COBOL procedural statements. If <%name%> occurs within an iteration block, the number of the current iteration will be used to determine which occurrence of the variable is to be used. If the program is running as a CGI Program, then the variable name refers to the name of the variable received in the HTTP GET or POST stream. If the program has been called by another program passing a parameter containing replacement variables, then the variable name refers to the variable received in the linkage section parameter as discussed below. While the variable replacement operation could be implemented with separate COBOL, sections without the need to define a new tag, the tags are preferred since they require much less coding by the programmer.

In the preferred embodiment of the present invention, there is also a language variable replacement tag having the form <$dataname$> or alternatively $$dataname$$. The language variable called "dataname" is substituted for this tag wherever the tag is found. The replacement occurs everywhere in the document, outside the COBOL tagged portion. The replacement does not take place within COBOL procedural statements. The variable called dataname must be declared as a language variable in the hypertext COBOL program. While the language variable replacement operation could be implemented with separate COBOL sections without the need to define a new tag, the tags are preferred since they require much less coding by the programmer.

As noted above, if the program is called by another program which passes the variables that are to be applied to the embedded COBOL program, these variables are accessed within the COBOL program in the same way as variables received from the HTTP GET or POST stream. The calling program (if any) may pass the following parameter: ##SPC1##

The above discussion can be more easily understood with reference to a simple COBOL-hypertext program. The program adds information to a database and displays the added information to the user. The hybrid file created by the programmer is as follows: ##SPC2##

This hybrid source file is converted by the COBOL pre-processor to a file that may be viewed as having a header/trailer which provides the interface to the MIME stream on the server and a COBOL section in which the material within the COBOL tags is reproduced and the material within the hypertext sections is converted to COBOL display statements. The header section is as follows: ##SPC3##

The actual input file is then converted to the following file: ##SPC4##

The trailer is as follows: ##SPC5##

While the above description of the present invention has been in terms of HTML and COBOL, it will be apparent to those skilled in the art that that the teachings of the present invention may be applied to any word processing format and computer language. The word processing file format is modified by defining a beginning and ending tag for the computer language segment.

The pre-processor for the computer language creates a source code file for the compiler in which output statements (e.g. in a COBOL implementation, DISPLAY statements are used) that, when executed, reproduce everything that is not enclosed by the language tags are inserted for the word processing file material. The code between the tags is copied to the source file. The executable file generated by the source code when compiled with the appropriate compiler or interpreter will then generate a word processing file in the word-processing format when executed.

Refer now to FIG. 1 which is a flow chart for a preprocessor according to the present invention. The pre-processor starts by writing any header information needed by the compiler or the operating system interface to the output file as shown at 12. This information may include the code needed to access particular input variables such as described above with respect to the HTML example.

The pre-processor then reads the input file until it finds a pre-processor tag that begins a computer language segment as shown at 13. The material from the input file that has been read prior to encountering the starting language tag is written to the output file as display statements in the computer language as shown at 14. The actual output sequence is a matter of design choice. For example, each line can be written as a single display statement as the line is read from the input file if the line does not contain a tag. Alternatively, the entire input stream from the input file since the last end tag can be stored and processed as a bloc in a single display statement. For the purposes of this discussion, a display statement is defined as any statement which will reproduce the material when executed in the resulting computer program.

The material from the beginning pre-processor tag to the ending pre-processor tag is then transferred to the output file as shown at 15. Any desired code translation can also be accomplished here. For example, the display tags described above with reference to the HTML embodiments of the present invention are expanded in terms of source language statements as part of this process.

When the end tag corresponding to the beginning pre-processor tag is encountered, the program checks for additional input. If the end of the input file is encountered, any trailers needed by the compiler and interface code are added to the output file as shown at 17. If there is more material in the input file, the program resumes reading the input file at block 13.

It should be noted that the pre-processor does not have to "understand" the word processor file formats. The pre-processor only needs to recognize the computer language tags. Any tag format can be used provided the word processing file format, or the embedded document, does not contain a tag of this form. Similarly, the word processing software does not have to "understand" the computer language tags; hence, no modifications to the word processing software are required. Finally, the computer language compiler also does not need to be modified.

In general, additional tags can be added to the definition. The replacement tags defined above are examples of such tags. Again, only the preprocessor needs to understand these tags. In addition, some form of interface tag that defines the inputs and output, i.e., a file, console, particular data stream, etc., will in general be useful.

It should also be noted that the present invention provides a means for defining a "live" document that may be easily transported between platforms. The source code provided by the pre-processor may be used on any platform that provides a compiler for that source code.

While the above described embodiments have referred to compiled computer languages, it will be apparent to those skilled in the art that the teachings of the present invention can be applied to interpreted languages such as BASIC and REXX.

The above described embodiments of the present invention have referred to a system in which the compiled computer language file resides on the server and is executed when a request for the "document" is received. However, it will be apparent to those skilled in the art from the above discussion that the source file may be stored instead. In such a system, the source file would be compiled the first time a request for the document is received. The operating system on the server can detect the need to re-compile the file by checking the time stamps on the source file and the executable file currently stored on the server. If the source file has been altered since the last compilation, the operating system causes the source file to be re-compiled prior to invoking the executable file.

Various modifications to the present invention will become apparent to those skilled in the art from the foregoing description and accompanying drawings. Accordingly, the present invention is to be limited solely by the scope of the following claims.

## Claims

1. A method for operating a computer to convert a word processing file, which comprises a linear sequence of characters, said linear sequence of characters comprising segments of said linear sequence marked by beginning and ending tags, into a source file comprising computer language statements, said source file defining a computer program that will generate an output stream in a format recognizable by a word processing program adapted to read said output stream, said method comprising the steps of: surrounded by said beginning and ending tags to computer language output statements and outputting said computer language output statements to said source file, source file, when said generated computer program is executed, to reproduce said linear sequence of characters in an output stream generated by said computer program; and corresponding to a segment of said linear sequence of characters that is surrounded by said beginning and ending tags.

2. The method of claim 1 wherein said word processing file comprises HTML.

3. The method of claim 1 wherein said computer language is COBOL.

4. The method of claim 1 wherein said tags occur in pairs, one marking the beginning of a sequence of characters and one marking the end of a sequence of characters, and wherein said pairs of tags are of first and second types, said first pair of tags marking sequences of characters that are to be copied to said source file without alteration, and said pair of tags marking sequences of characters that are to be translated to predetermined source code statements determined by an indication associated with said second pair of tags.

5. The method of claim 1 further comprising the step of providing computer source code statements in said source file enabling a program generated from said source file to receive input from a source outside of said generated computer program.

6. The method of claim 1 further comprising the step of replacing predetermined syntax in said linear sequence of characters that is not surrounded by said tags with variables defined outside of said linear sequence of characters.