Disp Menu; The Fix Function; The All Function; The Sci Function - HP -42S Manual

2.6 DISP Menu

The DISP menu is the first menu we have to see. It is above E key. So start by pressing
When you do this the DISP menu appears in the first line with the following functions.
FIX SCI
These functions appear just above the top row of keys ∑+, 1/x, √x, LOG, LN and XEQ. Now with
the DISP menu active those keys don't represent their original functions but those of the DISP menu.
The same happens with all menus.

2.6.1 The FIX function

The FIX "function" is not a function in the mathematical sense, but a calculator function. By
usingFIX function the display becomes with a fixed number of digits after decimal point. Ok, press
FIX. (I mean ∑+ with DISP menu active)When you do this what appears isFIX _ _Then you have to
enter a number up to 11. For example FIX 0 4 sets the calculator to have 4 digits of precision after the
decimal point. A number like π will appear as 3.1416 and √2 will appear as 1.4142.(You can verify
this by doing π and 2 √x respectively)
If you put FIX 0 9 than those numbers will appear as 3.141592654 and 1.414213562. It is important
to say that this is not the actual precision the calculator will have but just the display precision. To see
all calculator precision you have to press ALL in DISP menu (above LOG key). By doing so those
numbers will appear as 3.14159265359 and 1.41421356237. As you can see the numbers are not
truncated but rounded.
Not all numbers can be seem with a fixed decimal precision. If you put 4 digits for fixed precision the
number π will appear as 3.1416 but if one calculates 10
what you are going to see is 100,000,000.000 with 3 decimal digits. This happens because the
calculator cannot show more than 12 digits at a same line.

2.6.2 The ALL function

We already talked about the ALL function. It makes the calculator to show all of its precision.

2.6.3 The SCI function

The SCI function works just like FIX one but puts the calculator in "scientific" mode. The numbers
will be shown as a decimal number between 1 and 10 times a power of 10. For example 1000 will be
represented as 1.00E3 with you put the calculator in scientific mode with 2 digits. 1.00E3 means
3
1.00×10 . The π number will appear as 3.14E0.
Actually even when in FIX mode, the calculator will convert some answers to scientific notation. For
example if you calculate 1.0001-1 with FIX 3 you are not going to get 0.000 but 1.000E-4. This
means that the calculator is "smart" and shows the result in the best way as possible.
Exercise. Show that 1.0001 – 1 gives 1.000E-4 in FIX 3 mode.
Answer: First we put the calculator in FIX 3 mode by doing
Then we do 1.0001 ENTER 1 – and we get the answer.
As you can see, when you are in FIX mode a sign ■ appears on the right side of the FIX name in the
DISP menu. This means FIX mode is active. The same happens with SCI, ALL, etc.

2.6.4 The ENG function

The ENG function puts the calculator in engineering notation. It looks like scientific notation but now
the first number does not need to be between 0 and 1 but can be between 0 and 1000 and the power
will be always 3 manifold (corresponding to the magnitude prefixes such as milli-, micro-, kilo-,
mega-, etc. used in engineering units). For example: 100 will be represented by 100.E0 in ENG 2
ENG ALL RDX. RDX,
8
(do this by doing 8
DISP
DISP.
x
10 or by entering 1
E
FIX 0 3.
8)