34 Section 3: The Memory Stack, LAST X, and Data Storage
what happens as the stack is filled with the numbers 1, 2, 3, 4. (The
shading indicates that the contents of that register will be written over
when the next number is keyed in or recalled.)
T
t z y
y
x
Z
z y x
x
1
Y
y x
1
1
2
X
x
1
1
2
2
Keys:
1
v
2
v
T
x
x
1
1
Z
1 1 2
2
Y
2
2
3
3
X
2
3
3
4
Keys:
3
v
4
) (roll down),
( (roll up), and ® (X exchange Y). ) and ( roll
the contents of the stack registers up or down one register (one value
moves between the X- and the T-register). No values are lost. ®
exchanges the numbers in the X- and Y-registers. If the stack were loaded
with the sequence 1, 2, 3, 4, the following shifts would result from
pressing ), (, and ®.
T
1
4
1
1
Z
2
1
2
2
Y
3
2
3
4
X
4 3 4
3
Keys:
)
| (
®
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