Tikal-25 Manual - Calculator Operation
Data Entry
The calculator allows entering either 8 digit floating point numbers or numbers in the scientific format with up to 5 displayed mantissa digits and 2 exponent digits (see
Scientific Notation below). Internally Decimal is used which provides 128bit accuracy. Numbers with non overlapping 8-digit sequences can be entered as the sum of two 8digit numbers, such as 34567890
+ .12345678
= 34567890 displayed, but 34567890.12345678 stored.
At any point in the calculation, CLR can be pressed twice to reset the calculator to clear any errors, input and statistics mode and cancels the scientific notation display mode. Any stored number in memory will not be cleared, though.
When there is an error made while entering a number, pressing CLR once before entering any other operation key will reset the number to 0
The correction of an incorrect operation entry while there are incomplete operations in process is dependant on the table below:
| Incorrect Entry
| Desired Entry
|
| +,- |
×,÷ |
yx |
x√y |
| +,- |
CK |
CLR |
CLR |
CLR |
| ×,÷ |
CK |
CK |
CLR |
CLR |
| yx |
CK |
CK |
./. |
CLR |
| x√y |
CK |
CK |
CK |
./. |
CK means to simply press the correct key and continue
CLR indicates that the entry cannot be corrected safely to the desired entry for all conditions and that the problem has to be restarted.
When the statistics mode has been activated by pressing ∑+ "STAT" is shown in the display and the arithmetic operations are locked out. To reactivate them, the statistics mode has to be cancelled by pressing CLR twice.
Scientific Notation
To enter very large or very small number, scientific notation must be used, where the number is entered as a mantissa multiplied by 10 raised to some power (the exponent) such as -3.5034 × 1034
The entry procedure is to key in the mantissa (including its sign), then press EE and enter the power of ten, including the exponents sign.
The last two digits on the right side of the display are used to display the exponent of 10. Additional digits can be entered after pressing EE, but only the last two numbers pressed are retained in the exponent.
Regardless of how the mantissa is entered in scientific notation, the calculator normalizes the number, displaying a single digit to the left of the decimal point, when any function or operation key is pressed.
Example 1
753 EE displays 753 00
+/- displays 753-00 - after pressing EE, +/- affects the exponent
Continuing input with 43 displays -753-43
Entering any operator terminates the edition and displays the normalized form -7.53-45
Example 2
1.2345678 EE displays 1.2346 00
+/- displays 1.2346-00
Continuing input with 12 displays 1.2346-43
Entering any operator terminates the edition. While the display shows 1.2346-43, internally 1.2345678E-43 is stored
The decimal point of the entered mantissa must not be beyond the 5th digit from the left because the mantissa for scientific notation is limited to 5 digits in the display. Eight digits may be entered, but only 5 are displayed when
EE is pressed. The entire 8 digit mantissa is used for calculations. The scientific notation mode does not engage when more than 5 digits are entered left of the decimal point.
Data in scientific notation form may be entered intermixed with data in standard form.
The scientific notation can be removed from the display by pressing INVEE if the number is less than ±9.9999 × 107 and larger than ±1 × 10-7. Pressing CLR twice also cancels the scientific notation display.