The DO command has the same looping function as in Fortran. The ratfor DO does not require an end-of-loop statement number, since it applies to the following statement block or line. DO commands may be nested.

DO condition
	statement-block

condition defines the integer looping condition which has the general form I=J,K,L. Looping is maintained provided that J<=I<=K and I is incremented by L with every pass.

statement-block specifies the statement or statements executed if the condition is true. Multiple statements must be enclosed in $( and $) braces. Note that if a statement appears on the same line as the DO condition then it must be separated by a semicolon (;).

DO I=1,100; A(I)=0. # semicolon is essential here

DO I=1,100
A(I)=0.

DO J=5,20,2
$(
A(J)=0.; B(J)=1.
$)