My numbers don't come out to be exact decimals in mode i put my float on number 1 and im trying to look for e with is apparently suppose to be around 2.78 but my calculator only says 2.7

The selector you are asking about is the "decimal selector". The result displayed/printed, will be in a format according to the position that you have selected as follows:
f = floating (the result will be in the number of decimal places that were entered on the keyboard
4= fixed 4 decimal places (x.0000)
3= fixed 3 decimal places (x.000)
2= fixed 2 decimal places (x.00)
0= fixed 0 decimal places (x)
add 2= (add mode*,fixed 2 places) ($.00)
Note* "ad mode" automatically enters the decimal place when entering the number on the keyboard. If you enter "123", the displayed ammount will be "1.23". If you enter "1", the display will read ".01". This is a useful setting when adding a list of numbers in a dollars/cents format, however, be careful, if entering a whole dollar ammount "three dollars" be sure to enter the decimal point, or enter the number as "300". If you don't, the result will be ".03", instead of the 3 dollars you intended.

Scientific mode is a display mode. It concerns the display of results. If the number are too small or too large they will be displayed in Scientific mode, because the screen does not have an unlimited number of digit positions.

Regarding the dots. A number followed by a radix mark (decimal mark) is considered to be a floating number, while the same number without a decimal mark is considered an integer (whole number).
The CAS is able to do symbolic and exact calculations, so that distinction between floting and integer numbers is important. Sometimes, to force a result to be displayed in its decimal representation all it takes is to append a decimal mark at the end of an integer.
Hope it answers your queation.

Actually, you are getting an exact number (try writing 1/7 as an exact decimal number). If you want to convert a single result to its decimal approximation, press diamond ENTER. If you want all results to come out in decimal, press MODE, F2, then down-arrow to the "Exact/Approx" line, press right-arrow, select "APPROXIMATE", then press ENTER twice.

When you reach the FLOAT line and see the string of numbers 01 234 etc. you are supposed to use the right arrow to highlight one of the numbers in the string of digits. If for example you highlight the number 4 and validate, your results will be displayed with 4 decimal places.

If you want your calculator to display the results with 5 decimal digits:

1. Open the [MODE] configuration screen.
2. On first line highlight [NORMAL], if it is not already highlighted and press [ENTER] to validate.
3. Use Down arrow key once to reach the line Float 0 1 2 3 4 5 6 7 8 9
4. Use right or left arrow key to highlight the number 5 in the foregoing list (Float 0 1 2 3 4 5 6 7 8 9).
5. Press ENTER to validate your choice
6. Press [2nd][Quit] to exit the [MODE] configuration screen.

Hello,
Press [MODE]. Use arrow down to go to second line Float. Use left arrow key to move cursor to a number other than zero and press [ENTER]. If you highlight 2 your results will have 2 decimal digits, but if 0 is highlighted all results will be integers (no decimals).
Hope it helps.

This is a partial solution for I do not have the TI89 titanium with me.
1. The easiest way is to insert the decimal mark (. dot or , comma) at the end of one of the elements of the fraction (numerator or denominator).

Ex: if you enter 1/2 the calculator displays the fraction 1/2, but if you enter 1./2 or 1/2. or 1./2. it displays 0.5

2. You can also configure the EXACT/APPROXIMATE mode option of the calculator ( Press Mode then scroll till you see exact/approximate) then choose AUTO, EXACT, or APPROXIMATE.

In the EXACT option the calculator will perform exact algebra ( Pi remains Pi not 3.14159... ).
In the APPROXIMATE option, calculations are performed numerically (everything is treated as a decimal number.)

In the AUTO option the calculator will try its best to keep the results as exact as possible :
x/6 + 1/2 yields x/6 + 1/2
x/6. + 1/2 becomes .166666..x +1/2
x/6. + 1./2 becomes .16666..x +0.5

My suggestion ( if you allow me) : Leave the calculator set on AUTO, and convert to decimals as needed by putting the decimal mark at the end of an integer.

I hope it helps.

Hello,
The calculator has limitations. No matter what number of decimal places you specify in the floating mode format, If the absolute value of the number is less than 0.001 the number is displayed in scientific format :
[digit][.][digt][digit] ...up to [digit9] [E][-][2 digit exponent].
Here are somme screen capture that show you that.



As you can see the two screens overlap. Floating mode is set to 4 decimal places. As long as the absolute value is less than 0.001, the number is displayed in scientific format. However when that absolute value exceeds 0.001 the display reverts to the floating mode format you want.

When you manipulate very small or very large numbers, the floating point format cannot be used because of the limitations of the screen.
In this last screen capture Floating mode is set at 9 decimal places. I entered the electron charge. The line is pretty full.


Hope it clarifies things for you

Hello,
Your TI81 can only perform numerical calculation: It always give uour numbers. The TI89, a more sophisticated calculator, can of course do numerical calculation, BUT ALSO symbolic ones. You ask it for the derivative of sin(x) and it will give you cos(x).
Anyway, if you want a decimal result for you calculation above one of the numbers must have a decimal point (instead of writing 2PI write 2.PI.

The TI 89 can do exact calculations. But if you want approximate results any number in the sequence of operations must have the mark of a decimal. Numbers without decimal marks are considered integers, Integer numbers with a decimal mark are treated as floating point numbers ( meaning decimal).

Hope it clarifies things for you.

You have to set how the calculator handles numbers. To do this follow these steps: 1. Press the 'MODE' button. This brings up the calculator's main settings page. 2. Scroll down until you reach a field titled 'Exact/Approx...'. This is the setting for how the calculator handles numbers, whether it will show the exact answer (which is usually in fraction format) or whether it will show an approximate number (which will be in decimal format). 3. Press the right arrow which will bring up the options for that setting. You must now choose between three ways of handling numbers: -'1:AUTO' will determine which type of answer the calculator will give based on what numbers you want it to calculate (e.g. if you want an answer in decimal format just add a decimal somewhere in your problem). -'2:EXACT' will automatically display all answers in either whole number format or in fraction format. -'3:APPROXIMATE' will automatically display all answers in decimal format. 4. After you have selected one of those options press enter one more time to get out of the 'MODE' dialogue and return to the 'HOME' screen. Now try a problem and see what happens. Personally I like using 'AUTO' because then I don't have to keep returning to 'MODE' when I want either or. Hope this helped, I had the same problem when I first started using the TI-89.