Paper trays

Some printers, such as the Hewlett-Packard HP4si, have multiple paper trays. You can set up Dvips to take advantage of this using the `bop-hook` PostScript variable (see section PostScript hooks).

For example, suppose you have an alternate tray stocked with letterhead paper; the usual tray has the usual paper. You have a document where you want the first page printed on letterhead, and the remaining pages on the usual paper. You can create a header file, say `firstletterhead.PS', with the following (PostScript) code (`bop-hook` is passed the current physical page number, which starts at zero):

```/bop-hook { dup 0 eq { alternatetray } { normaltray } ifelse } def
```

where alternatetray and normaltray are the appropriate commands to select the paper trays. On the 4SI, alternatetray is `statusdict begin 1 setpapertray end' and normaltray is `statusdict begin 0 setpapertray end'.

Then, include the file with either