Reviewing the Stack

R(Roll Down)

The (roll down) key lets you review the entire contents of the stack by "rolling" the contents downward, one register at a time. You can see each number when it enters the X–register.

Suppose the stack is filled with 1, 2, 3, 4. (press 1 ‘2 ‘3 ‘4)

Pressing four times rolls the numbers all the way around and back to where they started:

T

1

 

4

 

3

 

2

 

1

Z

2

 

1

 

4

 

3

 

2

Y

3

 

2

 

1

 

4

 

3

X

4

 

3

 

2

 

1

 

4

What was in the X–register rotates into the T–register, the contents of the T–register rotate into the Z–register, etc. Notice that only the contents of the registers are rolled — the registers themselves maintain their positions, and only the X– and Y–register's contents are displayed.

Rµ (Roll Up)

 

The (roll up) key has a similar function to

except that it "rolls" the

stack contents upward, one register at a time.

 

The contents of the X–register rotate into the Y–register; what was in the T–register rotates into the X–register, and so on.

T

1

 

2

 

3

 

4

 

1

Z

2

 

3

 

4

 

1

 

2

Y

3

 

4

 

1

 

2

 

3

X

4

 

1

 

2

 

3

 

4

RPN: The Automatic Memory Stack 2–3