CALC 1 has the following ways to store/ recall numbers:
key copies the value from the x register into a storage variable. Storage variables a-z are general purpose user variables. If there was a pending formula, pressing STO then "u", for example, will evaluate the formula before storing it in the "u" variable.
key copies the value from the storage variable into the x register.
If you are entering a formula in chain mode, 5 + RCL b, the formula will be "5.00 + 12.00" for the value of 12.00 in b.
If you are entering a formula in algebraic mode, 5 + RCL b, the formula will be "5 + b".
So if you have a pending formula, RCL will insert the variable into the formula. Otherwise the value will be placed in the x register.
With Key Preview, tapping STO or RCL will display the value of the respective storage variable on the key. This feature makes it easy to see which variables are available and the values of used variables.
The last 200 results of every formula and key calculation is stored in the History list. The history list shows you the results along with the formula or key used to calculate it. Tapping the row will enter the value into the x register.
The Formula Calculators will automatically assume that if you enter a number or formula and tap one of the formula parameter keys that you wish to store the value. So after keying in "150", there is no need to tap =, then STO, then the "old" value key in the Percent Change calculator. Just tap "150" then "old". The "AS" indicator will appear in the display when Auto STO is active. See the Auto STO page. "Long press" the key and the hint will tell you if a Store or Calculation will take place.
The Automatic Stack keeps the last 4 results. Tapping SWAP and ROLL will bring the values to the x() register.
RPN users are familiar with the automatic stack. With CALC 1, users who prefer the chain calculation mode will also find the automatic stack useful in incorporating recent results in calculations. See the Calculations Using the Chain (CHN) Calculation Mode for an example.