HP -67 Owner's Handbook Manual page 134

130 Simple Programming
Press Display
Pressing twice more shows you that zeros have been loaded into
steps 003 and 004:
Press Display
SST 003 00
R 004 00
Pressing E58 again shows you that the operation loaded into step 005
is B 6:
Press Display
o 005 33 06
Thus, in order to load this portion of the program into the calculator
from the keyboard, you would have pressed the following keys:
o0
500
& 6
Remember that each step of program memory can hold a complete
operation, no matter whether the operation consists of one (e.g., & ),
two (e.g., B (M), or three (e.g., Bl EJ 9) keystrokes. You can see
that the 224 steps of program memory can actually hold many more
than 224 keystrokes.
In addition to the 224 steps of program memory in which you can load
keystrokes for programs, program memory also contains step 000. No
functions can be loaded into step 000, and in fact, step 000 serves
only as a kind of marker within memory, a convenient ''starting
point'" when you begin loading a program.
Any function on the keyboard can be loaded into program memory
except the five default functions, and certain editing functions like
38 .