# EPOC OPL Guide & Reference Glossary

## Index C

Term | Topic | Meaning | See Also
call | OPL Basics | To invoke a function with its arguments. When a function is called, it returns a value. | value, function, argument
character code | OPL Basics | The number representing a letter or symbol. |
character set | OPL Basics | All the letters and symbols which can be displayed. |
coercion | OPL Basics | Translating from one variable type into another when required. This isn’t done always. |
colour mode | Graphics and Interaction | A number representing the number of colours or greys that can be displayed. Constants for colour modes are supplied in `Const.oph`. |
command | OPL Basics | A straightforward instruction to OPL with no return value. | value, return
commit | Data File Handling | To write the changes of a database transaction. After changes are committed, they cannot be undone (rolled back). | transaction, database
condition | OPL Basics | An expression with a logical value used for program flow control. | logical value, expression
constant | OPL Basics | Names which can be used like variables, but whose value cannot change. |
content type | Advanced Topics | What sort of file a particular file is. MIME content types are written as a string such as “`text/html`” or “`image/jpeg`”. | MIME