Editing Expressions - Texas Instruments TI-82 Keystroke Manual

For now, it would be best to have all of the settings on each line highlighted (black background) as
shown. If any of the highlighted settings on your calculator are not the ones shown above, use your
Arrow keys to move the blinking cursor over the setting desired and press ENTER. Continue in a like
manner until all of the settings on the left side are highlighted as shown. Press 2nd [QUIT] to return to
the Home screen.

EDITING EXPRESSIONS

Turn on your calculator and type in
expression.) The calculator displays 3+2*7. Note that the calculator displays multiplication with an
asterisk (*). This is a common computer notation for multiplication.
Entering an expression and editing it before evaluation
As you can already see, the TI-83 differs from ordinary scientific calculators in more ways than just
being able to draw graphs. One of its major advantages as a calculator is that it enables you to see an
entire arithmetic expression as you enter it. The TI-83 also lets you easily edit the expression both
before and after you evaluate it. To see how to edit, we will change the expression above, replacing the
2 with a 4. Use the Left Arrow key (
expression should now look like this: 3+4*7. We will now evaluate the expression. The cursor is still
in the middle of the expression, but that doesn't matter. To evaluate the expression press the ENTER key
in the lower right-hand corner of the keyboard. On the right-hand side of the calculator screen you
should see 31 displayed, which is the value of the expression. Note that the calculator uses standard
algebraic order of operations rules, performing the multiplication before the addition.
Editing an expression after evaluation
Suppose you wanted to evaluate
one character (5 instead of 4), there is a way we can quickly obtain the new expression from the old.
Rather than enter the entire expression again, just press 2nd [ENTRY]. An exact copy of the last
expression entered is reproduced on the screen. Now use the arrow keys as before to change the 4 to a
5, and press ENTER to obtain the value of the new expression, 38.
INS (Insert) and DEL (Delete)
Suppose we want to evaluate
get 3+5*7 on the display. Move the cursor over the 5. We have one problem here that we must
recognize: if we type in 4.85, we will type over part of the expression we want to keep. To avoid that,
type the 4 over the 5, and then press 2nd [INS], which puts the calculator in Insert mode. Note that the
cursor becomes a blinking underline. That means that the character at the cursor position and all those
to the right of it will be moved to the right to make room for some inserted symbols. Type in the
remaining .85 to complete the 4.85 and see how the other characters are moved to the right to make
room. Now use the arrow keys to put the cursor at the end of the expression. Note that as soon as you
move the cursor with an arrow key, the calculator leaves Insert mode. We are now going to change 7 to
7.6. Since the cursor is at the end of the expression, the calculator need not be in Insert mode to make
this change (though it would make the change just the same if it were in Insert mode). After the 7 type
in .6, and press ENTER to display the value of the new expression, 39.86.
Now suppose we want to evaluate
reproduce the last expression, and use the arrow keys to place the cursor over the 4. Type in 5.2. Since
5.2 contains one less character than 4.85, the last digit of the 4.85 is still on the screen and must be
TI-83 On/Off, Contrast, Mode, and Editing Expressions
+ ×
3 2 7 . (Don't worry just yet about calculating the value of the
<
) to move the cursor until it is over the 2. Type a 4. The
+ ×
3 5 7 . Since this expression differs from the previous one in only
+ ×
by editing the last expression. If we press 2nd [ENTRY], we
3 . 4 85 7 6 .
+ × by editing the last expression. Press 2nd [ENTRY] to
3 5 2 . 7 6 .
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