Code tags usually style references to things like files names inline: comments.php, or things you should type exactly:

for file in *.html ; do mv $file `echo $file | sed 's/\(.*\.\)html/\1php/'` ; done


While pre tags make preformatted text in a block, like:

/*
 * Switch to stack of the new process and set up
 * his segmentation registers.
 */
retu(rp->p_addr);
sureg();
/*
 * If the new process paused because it was
 * swapped out, set the stack level to the last call
 * to savu(u_ssav).  This means that the return
 * which is executed immediately after the call to aretu
 * actually returns from the last routine which did
 * the savu.
 *
 * You are not expected to understand this.
 */
if(rp->p_flag&SSWAP) {
	rp->p_flag =& ~SSWAP;
	aretu(u.u_ssav);
}
/*
 * The value returned here has many subtle implications.
 * See the newproc comments.
 */
return(1);

that.