HP 35s Quick Start Manual page 45

Here is a step-by-step explanation of this program:
Program line B002 is an instruction to set ALG mode, to make
sure program B is not accidentally used in RPN mode. If you
always work in ALG mode, or if you always remember to switch
to the proper mode before using this program, then this pro-
gram line is not needed – but it is always safer to use it. A simi-
lar line, setting RPN mode, could have been used in program A
for the same reason.
Line B003 squares the value in the X–register and multiplies it
by π.
Figure 42
Enter the REGX instruction by using the < key and moving the
cursor to the left before pressing . REGX refers to the
value in the display – the X register. Since this program line is
wider than the screen, an ellipsis is displayed as shown in the
second screen image at right. To view the entire program line
when it is on the lower line of the screen, press Ö and the
entire line is displayed.
The instruction at line B004 stops program execution
Getting Started 41