The display is shown and the paper feed works but I cannot enter numbers when pressing the keys, what can be the problem? This is a new calculator that I haven't used since purchase

From page 31 of the manual in English, available on HP's website at the link below:
Number of Days Between Dates
To calculate the number of days between two given dates:
1. Key in the earlier date and press [ENTER].
2. Key in the later date and press [g][?DYS].
The answer shown in the display is the actual number of days between the two dates, including leap days (the extra days occurring in leap years), if any. In addition, the hp 12c also calculates the number of days between the two dates on the basis of a 30-day month. This answer is held inside the calculator; to display it,
press [X><Y]. Pressing [X><Y]again will return the original answer to the display.


http://www.hp.com/ctg/Manual/c00363319.pdf

Nothing of the sort. Just locate the EE key. You access it by pressing [2nd][x^-1]. It is the one below the [sin] function key.
To enter Avogadro's number
Key in
6.02 [2nd][x^-1] 23 [=/Enter]
If you divide by that number just enclose it between parentheses to ensure correct calculation.
You can also enter it as described 4 lines above, press the = key. The number will be displayed. To divide by it, press the [x^-1] key and its reciprocal will be displayed ready to be multiplied.

Use the DMS key marked degree, apostrophe, double quotation mark.
Lets us call it [DMS]
To enter an angle in degree minutes seconds or hour, minutes, seconds, type in the number of degrees, press the [DMS] key, enter the number of seconds, press the [DMS] key, enter the number of seconds then the [DMS] key. Press = the calculator displays the value in DMS units. If you press the DMS key again the number displayed is converted to decimal degrees.
Example:enter 12 degrees, 15 minutes, and 25 seconds
12 [DMS]15[DMS]25[DMS] =
Calculator displays 12 deg 15'25"
Press the DMS key again and you see 12.2569444

The Down Arrow and the View buttons are disabled on the T6050 as default because reverse paper feeding is not recommended on the T6050 printer because they only have one pair of tractors which are mounted above the platen. If the printer tries to reverse feed paper, it could cause a paper jam unless the platen gap is open sufficiently to allow the paper to feed down through the gap unhindered.
You can enable reverse paper feeding if you are sure that a paper jam will not occur. This is done as follows. Set the printer to Offline. Press the Mode key: display will show Offline Normal. Press any Arrow key until display shows Offline Oper. Press the Forms/1 key. Press any Arrow key until display shows Oper Forms. Press the CPI/2 key. Press any Arrow key until display shows Forms RevPap. Press the LPI/3 key. Press any Arrow key until display shows RevPap Enabled. Press the Enter key and reverse feeding will be set. Set the printer to Online. Once the reverse paper function has been enabled this option will need to be saved to prevent the setting being lost when the printer is powered off. To save the Menu Configuration; Put the printer OFFLINE Press the MODE button, then press the DOWN ARROW until CONFIG is displayed Press FORMS/1, then press the DOWN ARROW until PRINTER is displayed Press CPI/2, then press the DOWN ARROW until SAVE is displayed Press LPI/3, and with POWERUP shown in the display, press ENTER.

TI-5045 SV
ii
English.............................................................. 1
Fran?ais ............................................................ 6
Espa?ol ............................................................. 11
Portugu?s ........................................................... 16
Examples, exemples, ejemplos, exemplos .............................. 21
ILLUSTRATIONS ¦ FIGURES ¦ ILUSTRACIONES¦ ILUSTRA??ES
Removable tab
Languette
Leng?eta extracci?n
Alavanca usada para o rolo
Ink roller
Rouleau encreur
Tamp?n de tinta
Cartucho de tinta
1
English
Your Texas Instruments calculator has a built-in printer for producing a permanent record printout of
your calculations with negative numbers printed in red. A big, easy-to-read display also enables you to
check entries or perform quick calculations without printing.
GETTING STARTED
OFF ON PRT IC GT
POWER
1. Connect the calculator to a proper power outlet (110-120V or 220-240V
where available).
2. The calculator is turned on by setting the POWER switch to the PRT
position.
Inserting the paper (see illustrations 1, 2, 3, and 4 on page ii).
1. Turn on the calculator.
2. Open the printer compartment cover by pressing down on its front edge and sliding it back in the
direction of the arrow.
3. Fit the roll of paper on the holder so that it unrolls from the bottom, with the loose end toward the
calculator.
4. Cut the end of the paper squarely and insert it firmly into the printer slot on the back of the
calculator.
5. Press & until the paper is in the printing position.
Replacing the ink roller (see illustrations 5 and 6 on page ii)
1. Turn the calculator off and tear off the excess paper.
2. Remove the printer cover by pressing down on both sides of the front edge and sliding back in the
direction of the arrow.
3. Remove the old ink roller by lifting it with the removal tab.
4. Insert the new ink roller into the compartment and press down gently until it snaps into place. Close
the printer compartment.
Note: The old ink rollers should not be refilled. Replacement rollers can be obtained from your local
retailer. The warranty does not cover ink roller replacement.
2
SELECTION SWITCH SETTINGS
OFF ON PRT IC GT
POWER ROUND
: 5/4 9 + F 0 2 3
DECIMAL
4
TAX
SET CALC
Set the POWER, ROUND, DECIMAL and TAX switches as required.
Note: The TAX switch is spring-loaded to return to CALC when it is moved to SET and released.
The switch settings are summarized in the following table:
SWITCH SETTING FUNCTION
POWER ON
PRT
IC
GT
No printout is provided; however, the display can be printed by pressing
4.
The printer provides a printout of your calculations but does not count them.
The printer is on and an item count of additions and subtractions to or from
the register is printed when sub-totaled or totaled.
The GT position controls whether or not the totals from the independent add
register are accumulated in the grand total register.
ROUND Rounds the result of a calculation to the selected number of decimal places.
:
5/4
9
Truncates the result to the selected number of decimal places.
Rounds the result up or down according to its value. For example, when the
DECIMAL switch is set to 2, the result is rounded up if the third decimal
position is 5 or more and rounded down if it is 4 or less.
Rounds the result up to the selected number of decimal places.
Ex. 220 P 6
Setup: PRINTER: PRT, ROUND: :
DECIMAL: 2, TAX: CALC
Ex. 220 P 6
Setup: PRINTER: PRT, ROUND: 5/4
DECIMAL: 2, TAX: CALC
Press Display Printout Press Display Printout
2 0. 0¦ C
220 ' 220. 220¦ P
6 3 36.66 6¦ =
36¦66 ?
2 0. 0¦ C
220 ' 220. 220¦ P
6 3 36.67 6¦ =
36¦67 ?
DECIMAL + Add mode: All results are given with two decimal places. For addition and
subtraction only, a decimal point is automatically placed to the left of the last
two digits entered, unless the number already includes a decimal point.
F Floating mode: Any results are displayed and printed with the maximum
number of decimal places.
0 2 3 4 Fixed decimal mode: Sets the number of decimals to 0, 2, 3, or 4.
3
TAX SET
CALC
Lets you enter a tax rate to perform tax calculations.
Stores the tax rate. Pressing ! or " after a tax rate has been entered,
adds/subtracts the stored tax rate to/from the value in the display.
Ex. VAT = 17.5 %
100 + VAT
Ex. VAT = 17.5 %
235 - VAT
Setup: PRINTER: PRT, DECIMAL: F, ROUND: 5/4, TAX: CALC
Move and hold the TAX switch to SET. Press 217 L 5 and release the TAX switch. It
automatically returns to CALC. 17.5% is printed.
Press Display Printout Press Display Printout
2 0. 0¦ C
100! 117.5 100¦
17¦5 @
117¦5 ?
2 0. 0¦ C
235" 200. 235¦
N35¦ @
200¦ ?
Note: The most common setup is POWER: PRT, ROUND: 5/4, DECIMAL: 2, TAX: CALC. Use these
positions for the examples unless other settings are given.
KEY DESCRIPTIONS
Basic keys
I Clear Entry: Clears an entry, enabling you to enter another number in its place. Note
that this key does not clear the add register.
2 Clear Key: Clears the add register, any pending operations, and the display. 0.C is
printed. Does not clear the memory.
( Right Shift: Deletes the right-most digit entered from an entry before an operation key is
pressed. Shifts the remaining digits one place to the right.
L Decimal Point: Enters a decimal point.
4 Date/Non-Add: Prints a date (such as 12¦10¦96) or a number for reference purposes.
Does not affect calculations. This entry is printed on the left side of the printout, the date
or number preceded by the # sign.
& Paper Advance: Advances the printing paper.
Addition and subtraction keys
9 Add: Adds a number to the add register. Displays the cumulated result.
: Subtotal: Gives the intermediate total from the add register. Using this key does not
affect the contents of the add register.
. Subtract: Subtracts a number from the add register. Displays the cumulated result.
E Total: Gives the total from the add register, and then clears the register.
4
Multiplication, division, percent and margin keys
? Multiply: Multiplies the number in the display by the next value entered.
' Divide: Divides the number in the display by the next value entered.
3 Equals: Completes any pending multiplication or division operation.
> Percent: Calculates percentages, ratios, add-ons (e.g. of VAT), or discounts.
# Gross Profit Margin: Calculates the selling price of an item when its cost and gross
profit (or loss) margin are known; also used to obtain a price excluding VAT.
Ex.
Cost: 594
Profit margin: 40%
Press:2 594 # 40 3
Answer:
Selling price: 990
Gross profit: 396
Ex.
Selling price including VAT: 252
VAT %: 20%
Press: 252 # 20 . 3
Answer:
Selling price excluding VAT: 210
VAT: 42
/ Grand Total: Gives the grand total of the operations previously performed and stored in the
Grand Total register. Every time a total is obtained with E it is cumulated into this register
(printout shows G+) which is only cleared when / is pressed twice. During long
calculations, if / is not used, this re

There are several reason why the Ti89 family of calculators might experience this inability to not shut off. Mainly, it has become known that foreign material or, static charges can get into the ports causing this malfunction. Other reasons are related to the OS, APP's and, 3rd party programming.

Generally, reinstalling the operating system takes time and, you can destroy some of your previous work. My aim here is to give you some instructions so, that you can get your calculator operating properly in the least amount of time.

(Procedure 1).

Check and see if there is any dust in the IO ports. Figure 1, shows where and what the IO ports look like and, gives some idea where they are located at the top of the calculator.
Figure 1.

Now look into both ports. Do you see any lose dust or material inside. If so, real gently with something small and non-metal (like a tooth pick), see if you can get any lose dust and debris out of the holes.

Warning! "Do Not Use Force To Get Obstructions Out".

Once you have the ports as clean as you can, blow into them with about a one second bursts. Make sure you do not spit! Now press [2nd] key and the [ON] key to turn the calculator off. Did the calculator turn off? If yes, then your done. If no, go to (Procedure 2).

(Procedure 2).

On the TI-89 family, press and hold the [2nd] key, left arrow, and right arrow; then press and release the [ON] key. This should reinitialize the operating system, in which you should see a progress bar filling on the screen. This is in hope that if any internal program was running it will now be turned off. On the TI-92 family or Voyage 200 can do the same procedure just use the [HAND] key in place of the 2 arrow keys. Now press [2nd] key and the [ON] key to turn the calculator off. Did the calculator turn off? If yes, then your done. If no, go to (Procedure 3).

(Procedure 3).

1. Press [F5], If successful the screen will display as shown below. Goto step 2.

2. Press [Diamond] [Clear], If successful the screen will display as shown below. Goto step 3.

3. Press [alpha] [S] No screen shot could be given. Go to step 4.

4. Press [0], This key is the number zero and, not the letter O. Make sure you enter the number 0 to RETURN to the Home screen. If successful the screen will display as shown below. Goto step 5.

5. Press [2nd] [Quit], If successful the screen will display as shown below. Goto step 6.




6. A repeat of (Procedure2). On the TI-89 family, press and hold the [2nd] key, left arrow, and right arrow; then press and release the [ON] key. This should reinitialize the operating system, in which you should see a progress bar filling on the screen. On the TI-92 family or Voyage 200 can do the same procedure just use the [HAND] key in place of the 2 arrow keys. If successful the screen will display as shown below. Goto step 7.

7. Now press [2nd] key and the [ON] key to turn the calculator off. Did the calculator turn off? If not go to (Procedure 4).

(Procedure 4).

Steps to re-installing the operating system:

• Connect the TI Connectivity cable between the PC and the calculator.
• Click on Start >> Programs >> TI Tools >> TI Connect >> TI OSDownloader
• Follow the on-screen directions to reinstall the calculator's OS.

Turn calculator ON
If you do not see icons, press MENU key.
Use arrows to move focus on the RUN application and press EXE
Press the [OPTN] button.
A set of thumbnails (TABs) appear on the lower part of the display screen.
Each Tab/Menu is activated by the Function key just below it.
Press the F6 Key corresponding to the right pointing arrow
Press [F3:Prob] to reveal the probability functions.

That is what you see


If you press the F6 key you get the other options.

On the first screen above, the nPr menu corresponds to the permutations, while the nCr menu corresponds to the combinations.

To use them you need to enter n (the larger value), press the key corresponding to the calculation (F2 for nPr and F3 for nCr) and then press the smaller number (r). See screen below.

While the menus are displayed at the bottom of the screen you can use the other calculator keys to enter number, etc. As long as you do not press the Function Fx keys you wont activate them.

On the screen

1. I set my calculator to the screen that is shown on the first screen capture
2. I enter 15
3. I press the F3 key: the Bold C is inserted after the number 15
4. I type in 6
   
5. To get the number of combinations that select 6 objects out of 15 ones (15C6) I press the [EXE] key.
6. Result is 5005
   

To respect the wishes of the asker, I showed all the steps, with screen captures to support the text. That is time consuming.
If this post happens to teach you something, please take the time to rate it accordingly. To show you apprerciation.

Hi. Many of the fx 9750's functions are hidden; they are accessed via the 6 grey F keys under the display. To use Int, Frac, Abs functions, after you turn on your calculator, in normal mode (menu 1 selection), press [OPTN] [F6] [ F4]

This will give you the number menu, containing Abs, Int, Frac, Rnd and Intg
Int is the F2 key. Press [F2] first, then enter number or variable. Int value will be shown.

Hope this helps.

Okay just figured this one out but on the back of the claculator there is a slip slid paper in that Press the feed key and allow the paper to feed through the claculator if it doesn't feed through push the paper in a little and hit the feed key again. It worked for me

Hi, I had the same problem...but I fixed it. Here's how: At the very back of the calculater under the paper roller there is a very thin horizontal slot. Insert the tip of the paper roll into the slot, then press the paper advance button located on the top left hand sidw of the calculator until you see the paper. Guide the paper through the top slot and voila.