Memory Keys

Almost every calculator has them — MC MR M+ and M− — and almost nobody is ever taught what they do. They're not complicated. Memory is just a single number the calculator holds onto in the background while you work, so you can set it aside and call it back whenever you need it.

What Each Key Does

M+ Add — Adds number currently on the display to whatever is in memory. If memory is empty, this is how you put a number into it the first time. Press it again later and the new number is added to the running total.

M− Subtract — Subtracts number on the display from what's in memory. Useful for keeping a running balance — add some figures in, take others out.

MR Recall — Brings stored number back onto the display so you can use it in a calculation. Memory isn't emptied;you can recall the same value multiple times.

MC Clear — Empties memory and resets it to zero. Do this whenever you're done with a stored value and want a clean start.

M Indicates Memory Is In Use

When there's a number in memory, a small M appears on the lower left side of the display along with the value being held, so you know memory is active and what it contains. When you clear memory with MC, the indicator goes away.

A Simple Example

Say you're totalling a few purchases and need to subtract a refund:

Press 4 0 M+ — memory holds 40
Press 6 5 M+ — memory now holds 105
Press 1 0 M− — memory now holds 95

You did three separate entries without writing anything down, and the running total was waiting for you the whole time.

How Memory Is Different From History

It's easy to confuse the two, but they do different jobs. History is a record, a list of calculations you've already completed, there to look back on. Memory is a single working number you're actively building and recalling as you go. Use history to review and reuse past results;use memory to hold a running total while you work on something else.

Your Memory Stays Put

Whatever you store is saved in your browser the moment you store it, so it survives closing the tab. Leave a value in memory, come back tomorrow, press MR, and it's still there, right where you left it. When you want it gone, MC clears it.