The TI-108 is a basic four-function calculator. It is heavily based on the Texas Instruments TI-108. It is, of course, not an actual Texas Instruments product. It features a solar panel for battery conservation, order of operations toggling, and memory for the storage of a number for later retrieval.

The 3 indicators on the left are:

M

This indicator will be greyed out when the memory value is 0. When the memory value is not 0, this indicator will be black.

—

This indicator will be greyed out when the currently displayed value is positive, and black when it is negative.

E

This indicator will be greyed out in most circumstances. It will turn black if your calculation returns a solution which either exceeds the display limits (-99999999 <= x <= 99999999) or is invalid (e.g. 1 / 0, √-1). When it's black, you must press the 'ON/C' button to continue your calculations.

There is a limit of 8 digits; accordingly, the maximum result your calculation can return is 99,999,999 and the minimum value it can return is -99,999,999. Results outside these limits will cause the calculator to error out. Also please note that due to the display limits, precision will be an issue past 7 decimal points.

Press this button once to set the current display value to 0. Press it a second time to clear all calculations/running totals.

When MDAS is on, the operations buttons can be pressed more than once in succession to operate with the current display value. For example 3+= would return 6 (3 + 3).
3++= would return 9 (3 + 3 + 3).
3++**-= would return 30 (3 + 3 + 3 * 3 * 3 - 3).
Pressing the equals button more than once does nothing.

When MDAS is off, pressing the operations buttons more than once would cause the operation to be performed on the current display value. For example 3++**-= would return 0 (since the last display value of 20736 would be subtracted by itself). Pressing equals more than once repeats the last operation. For example 3+2*5=== would return 625 (25 * 5 * 5).

The '+/-' button toggles the display value from positive to negative. You can see the current status on the indicator.

The '√' button calculates the square root of the current display number in place.

The '%' button calculates the percent of the last displayed number in place. For example, 12+10% would display 1.2. If there is no last displayed number, it will return the display number divided by 100. For example 10% would return 0.1.

Neither the '√' or the '%' buttons are affected by the MDAS setting.

The three buttons which store and retrieve a number from memory are M+, M-, and MRC. You can see if the memory has a non-zero value by looking at the indicator.
M+ adds the current display value to memory.
M- subtracts the current display value from memory.

If adding or subtracting the current value to the memory value would cause an overflow, the addition/subtraction will not be made and the calculator will error out.

When pressed once, pressing MRC Recalls the memory value. Pressing MRC a second time will Clear the memory.

Calculator button

Keyboard key

0 - 9, .

0 - 9, . (numpad or regular keys)

ON/C

Z or Space

+

+

-

-

×

*

÷

/ or \

=

Enter or =

%

%

√

$

+/-

#

M+

M

M-

N

MRC

B

toggle MDAS

` (backtick key)

Bring up this help menu

H