Section 6
The Standard Function Catalog
The HP-41C has over 130 internal functions that allow you to compute answers to problems quickly and accurately. You can list this set of functions at any time by pressing g CATALOG 3.
This section gives a brief explanation of most HP-41C standard functions (except programming functions, which are presented in part II) along with some example problems. All of the functions in this section can be stored and executed in program memory as part of a user program unless otherwise noted. Remember, execution of all functions not on the keyboard is simple when you assign the functions to the USER mode keyboard for execution (refer to section 4).
General Mathematics Functions
Changing the Sign of a Number
To key in a negative number, press the keys for the number, then press CHS (change sign). The number, preceded by a minus (–) sign, will appear in the display. You can also change the sign of either a negative or positive nonzero number in the display by pressing CHS . For example, key in 2.54 and change the sign of the number.
Keystrokes Display    
2.54 _
  The number
2.54 _
  The sign is changed.
2.54 _
  Sign is changed back again.
To change the sign of an exponent of a number, you must use CHS immediately after keying in the exponent (before you perform some operation that terminates digit entry). As soon as digit entry is terminated, CHS  changes the sign of the mantissa of the number, not the exponent. For example, key in the Rydberd constant (1.0973731 × 107, a universal constant used in spectroscopy) and change the sign of the exponent.