HP -16C Owner's Handbook Manual page 75

Section 7: Programming Basics 73
Keystrokes in Program mode become program instructions
occupying program lines. These numbered lines indicate the
calculator's position in program memory. Line 000 marks the
beginning of program memory and cannot be used to store an
instruction; the first line that contains an instruction is line 001.
No program lines except 000 exist until instructions are stored in
them.
Programs are usually started at line 001, though you can start a
program at any existent line. As you enter instructions, any
existing programs will be preserved and '"bumped" down in
program memory, thereby incrementing their line numbers.
Beginning a Program. Clearing program memory will erase all
programs in memory and position the calculator to line 000. To do
so, press [f]JCLEAR in Program mode.
If the calculator is not at line 000 and you do not want to clear
program memory, you can position the calculator to line 000 by
pressing CLEAR [PRGM] or (] 000 in Run mode, or by
pressing (] 000 in Program mode. (The (-] instruction
cannot be recorded.)
A (label) instruction—[d] followed by a digit or letter
label {0 to 9, A to F}—is used to define the beginning of a program
or routine. The use of labels allows you to quickly select and run a
particular program or routine.
Keystrokes Display
CLEAR 000- Clears program memory
and sets calculator to
line 000 (start of
program memory).
(g](LBL]A 001-43,22, A Keycode for label "A".
Recording a Program. A program consists of the same
keystrokes you would use to solve a problem manually. Keys
pressed in Program mode are recorded in memory as programmed
instructions.* The display contains a line number and keycode(s).
Keycodes are one- or two-digit numbers indicating the position of
keys on the keyboard (described in more detail later).
* Except for the nonprogrammable functions, which are listed on page 81.