Information such as a return address line on an address label or a heading over a list can be entered directly into the project as "fixed text". Fixed text is printed exactly as it is held in the project.
Alternatively, this information can be taken over dynamically from a higher-level program. Such information is entered into the projects as "variables" or "fields".
Variables and Fields
Consequently, a distinction is made between two types of data fields: on the one hand there are data fields that are filled with content once per printed page (once per label or file card), these are called "variables". On the other hand, in a report, there are data fields that are filled repeatedly with different contents for a page, e.g. the data fields of an item list of an invoice. These data fields are called "fields". These fields are only available in tables, crosstabs, charts, and in the report container.
For this reason, in file card or label projects only variables can be used, while in list projects both variables and fields can occur. For printing an invoice, an application would typically declare the invoice header data such as customer name and address as variables, while the item data such as article number, unit price, description etc. would be passed as fields.
Formulas and Expressions
Using variables and fields alone, you can create appealing projects that are sufficient for many purposes. However, the Designer offers much more. With the aid of formulas and expressions, the information held in variables/fields and fixed text can be joined or modified in almost any conceivable way. The "formulas" and "expressions" make this possible. In formulas and expressions, fixed text and variables/fields can be used in "functions" and joined by "operators".
For example, with projects for printing address labels, you can use an expression to automatically add the text "PO Box" to a PO Box number held in a variable called POBOX. In this way, not just the number alone will be printed on the label but something like "PO Box 111111" instead.
Or, consider this: The net price of an article is held in a field called PRICE. However, you want to print the price including VAT in your list/table. A formula that calculates the VAT from the net price and then adds it on will help you here. The gross price will then be printed.