Hello, I'm Kimi, an expert in the field of calculators and their functionalities. When it comes to the keys labeled "M" and "M+" on a calculator, they are part of the memory functions that are often found on scientific and graphing calculators. These keys allow users to store numbers in a memory register for later use, which can be particularly helpful in complex calculations or when working with multiple variables.

The "M" key is typically used to store the current display value into the memory. This is known as the Memory Store function. When you press "M", the calculator takes the number that is currently shown on the screen and saves it into its memory. This stored value can then be recalled later using the "MR" key, which stands for Memory Recall.

The "M+" key, on the other hand, is used to add the current display value to the value already stored in the memory. This is known as the Memory Add function. When you press "M+", the calculator adds the number on the screen to the number in the memory and then stores the new total back into the memory. This function is very useful when you want to accumulate a running total or sum a series of numbers without having to write down intermediate results.

In addition to "M" and "M+", there are a few other memory-related keys that you might find on a calculator:

- MR: This key is used to Recall the value from the memory register. It brings back the number that was previously stored without affecting the current display value.
- MC: This stands for Memory Clear. Pressing "MC" will clear the memory register, setting its value back to zero. This is useful when you want to start a new set of calculations without the old stored values interfering.

It's important to note that the functionality of these keys can vary slightly between different models and brands of calculators. Some calculators might have additional memory functions or different key labels. However, the basic principles of storing, adding to, and recalling values from memory remain consistent across most calculators.

Now, let's move on to the translation of the above explanation into Chinese.

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Old or simple calculators have a memory register - essentially a second calculator that can handle addition/subtraction only. M+, M-: Add (or subtract) the current value to (or from) the stored value in the memory register. MR : Recall the current memory register value. MC : Clear the memory register (set to zero).read more >>