HP 39gII User Manual page 240

Program
Structure
Comments
230
specified as the first argument. The default is G0, which
always contains the currently displayed screen. Thus, the
full syntax for the PIXON command is:
PIXON([G,] xposition, yposition [ ,color]);
Some built-in commands employ an alternate syntax,
whereby function arguments do not appears in
parentheses. Examples include RETURN and RANDOM.
Programs can contain any number of subroutines (each of
which is a function or procedure). Subroutines start with
a heading consisting of the name, followed by
parentheses that contain a list of parameters or
arguments, separated by commas. The body of a
subroutine is a sequence of statements enclosed within a
BEGIN END; pair. For example, the body of a simple
program, called MYPROGRAM, could look like this:
EXPORT MYPROGAM()
BEGIN
PIXON(1,1);
END;
When a line of a program begins with two slashes, //,
the rest of the line will be ignored. This allows the
programmer to insert comments in the program:
EXPORT MYPROGAM()
BEGIN
PIXON(1,1);
//This line is just a comment.
END;
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