You'll notice the use of quite a few uppercase identifiers in HELLOWIN.C. These identifiers are defined in WINDOWS.H.
Several of these identifiers contain a two-letter or three-letter prefix followed by an underscore:
| CS_HREDRAW | DT_SINGLELINE | WM_DESTROY |
| IDI_APPLICATION | CS_VREDRAW | DT_CENTER |
| WS_OVERLAPPEDWINDOW | IDC_ARROW | DT_VCENTER |
| WM_PAINT | CW_USEDEFAULT |
These are simply numeric constants. The prefix indicates a general category to which the constant belongs, as indicated in this table:
| Prefix | Category |
| CS | class style |
| IDI | ID for an icon |
| IDC | ID for a cursor |
| WS | window style |
| CW | create window |
| WM | window message |
| DT | draw text |
You almost never need to remember numeric constants when programming for Windows. Virtually every numeric constant used in Windows has an identifier defined in WINDOWS.H.