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

Z Y X

1

2

3

4

4

1

2

3

3

4

1

2

2

3

4

1

1

2

3

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

Z Y X

1

2

3

4

2

3

4

1

3

4

1

2

4

1

2

3

1

2

3

4

RPN: The Automatic Memory Stack 2–3

Page 43
Image 43
HP 33s Scientific manual Reviewing the Stack, ¶ Roll Down, Rµ Roll Up