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Chapter 16: Glossary of On-line Help Terms

The Net Express Help might introduce some new terms to you. This section defines what they mean.


A bookmark is a user-defined index entry. You set a bookmark at any point in any topic and give it a name. This is then stored, in alphabetic order, in a list of bookmarks. Bookmarks are retained between executions of Hyhelp and On-line. Accessing a defined bookmark from an alphabetically ordered list immediately displays the topic it is attached to. It is useful to attach bookmarks to frequently accessed topics. However, they can also be used as a temporary means of marking your place while you go off and browse other topics.

Browse Chain

A browse chain is a sequence of topics that the author of the on-line help file has chained together. The chain can be browsed forwards and backwards by the user. This facility should be used to connect together topics of a similar subject. If no browse chains are defined, the whole file becomes a browse chain with each topic chained to the physically preceding and following topics.

Character Graphics

When creating a topic, pictures can be created from the standard characters available. These are called character graphics. In order to maintain the vertical alignment of these graphics the lines are blocked together using the :cgraphic and :ecgraphic tags. The access and display programs ensure that the vertical alignment is maintained when a character graphic block is displayed, by specifying a monospaced font for those lines.

Context Number

Every topic has a unique context number that is used to reference that topic. The context number is used as an index into a look-up table held in the file which defines the address of each topic within the file.

You can choose the topic number and define it using a .define tag. The numbers are purely arbitrary and do not reflect the structure of the file. The sequence of the topics in the source files is the only structure recognized.

More than one context number can point to the same topic.

Cross-reference List

A cross-reference list is a special sort of fixed-lines topic where each line contains a cross-reference to another topic. Such a topic is defined using the .list tag. It must not contain any formatting tags. When displayed, a full width cursor appears. This can be used to select a line to which you wish to cross-reference.

The first word on the line is used as the cross-reference name unless it is defined as a hotspot, in which case the hotspot cross-reference is used.

External Topic-name

External topic-names are used if a topic is going to be accessed from an external source. These names are held in a tree structure within the on-line help file. When a topic-name is used in a search or on entry to the access and display systems the tree is searched for the name.

Fixed-lines Block

Blocks of lines within a topic can be identified as being fixed lines. They are displayed exactly as written with no formatting. If no vertical alignment is needed, such a block is defined using the :lines and :elines tags. If vertical alignment is to be maintained, you must define the block as a character graphic.


A flexi-text topic is formatted dynamically at display time to fit within the sides of the topic window so that no horizontal scrolling is necessary. Note that fixed-lines blocks can extend beyond the right-hand edge of the window.

History List

When displaying topics, the title of each topic displayed is recorded in the history list. By accessing the list any topic previously visited can be identified and revisited. The history list holds the last 40 items visited in the current session.

Home Topic

The home topic is the very first topic in the first source file used to create an on-line help file. The home topic is displayed whenever Hyhelp or On-line is specified with a filename but no topic-name. Additionally, the Home function causes the home topic to be displayed.

The home topic should always contain a very brief overview of the information supplied in the file, and provide hotspots to enable the user to get to the various parts of the file.


A hotspot is an area within a topic which, when activated, causes another topic to be displayed. Hotspots should be identified by using consistent highlighting.


IPF is name of the help facility used with OS/2 Presentation Manager. In the On-line Help System, IPF tags are preceded by a colon (:) and followed by a period (.).


A list is a structure within a topic that is displayed in a specific way. Each list consists of a set of items, the start of each item being identified by an appropriate tag. The start and end of each list is also identified by a tag. A list item can contain further lists. The presentation of these embedded lists reflects the depth of embedding.

There are several types of lists: simple lists, unordered lists, ordered lists, definition lists and parameter lists.

Local Topic-name

A local topic-name is a topic-name that can only be referenced from within a single on-line help file. Such a name is identified by a leading "at" character (@), although this does not apply to IPF tags. Ohbld converts all local topic-names to context numbers. Local topic-names cannot start with a digit.

On-line Help File

An on-line help file is a file with extension .hnf that is created by Ohbld from a source information file.


Tags are control words embedded within the source files that define how the file and topics are created. Some of the tags are used to define structures within the text so that the text can be reformatted dynamically within the display window.


The on-line help is made up of topics. A topic is the single entity which is displayed in a window. All of the topic can be seen by scrolling or paging. A subject can contain several topics using hotspots to cross-reference each other. The Net Express Help uses this method where, for example, the subject PERFORM is made up from several cross-referenced topics.


Every topic has at least one name attached to it. Local names are used internally to reference the topic. These are converted to context numbers. External topic-names are held in a tree structure within the on-line help file. When a topic name is used in a search or on entry to the access and display system the tree is searched for the name.

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