request to leave one space:.sp{ }{1} make sure there are at least 3 lines left on the page:.ne{ }3 center the next line:.ce{ }{1} indent 5 spaces:.in{ }5 stop filling lines:.nf start filling lines:.fi start adding spaces between words so that right margin is even:.ad stop adding spaces between words to make right margin even:.na define page heading test for all pages:.he{ }{''''} define page heading for even numbered pages:.eh{ }{''''} define page footing request:.fo{ }{''''} temporary indent 12 spaces to the right:.ti{ }+12 underline next three input lines:.ul{ }3 make 2 blank pages (except for headers and footers):.sk{ }2 force the beginning of the next page:.pa set the current page number to 20:.pn{ }20 execute `roff' command for the document file named `abc':roff abc execute `roff' of file `letter' but print only from page 3 on:roff +3 letter what symbol stands for the page number in headers and footers:% how would you translate `;' to `-':.tr{ };- temporarily indent 4 spaces left:.ti{ }-4