Windows also uses an extensive list of predefined constants that are used as messages, flag values, and other operational parameters. These constant values are always full uppercase and most include a two- or three-letter prefix set off by an underscore. Here are some examples:
| CS_HREDRAW | CS_VREDRAW | CW_USERDEFAULT |
| DT_CENTER | DT_SINGLELINE | DT_VCENTER |
| IDC_ARROW | IDI_APPLICATION | WM_DESTROY |
| WM_PAINT | WS_OVERLAPPEDWINDOW |
In the case of constant identifiers, the prefixes indicate the general category of the constant. Table 2.2 shows the meanings of the prefixes in the examples shown here.
Table 2.2: A Few Constant Prefixes
PrefixCategory
| CS | Class style |
| CW | Create window |
| DT | Draw text |
| IDC | Cursor ID |
| IDI | Icon ID |
| WM | Window message |
| WS | Window style |