|DO||[Start of a loop (Scripting operation)]|
|LB||[Label for jump operation or end of DO-loop (Scripting operation)]|
1. <REG> is a loop index variable where the value of the index is accumulated. (SPIDER still accepts an earlier syntax where <REG> was a single letter (a...z or A..Z) which denotes the loop index).
2. <LOWER> is a integer constant that specifies the lower bound of the loop index.
3. <UPPER> is a integer constant that specifies the upper bound of the loop index.
4. <INCREMENT> is an optional integer constant that specifies an incremental value that is added to the loop index with each cycle of the loop. Default value for <INCREMENT> is 1.
In the above example, DO will repeat any operations (~~~~~) with the loop index variable [imgnum] varying from 5 to 17.Modeled after the FORTRAN 'ENDDO' syntax.