# The Calculator popdown

If you ever need to perform calculations while using the Cambridge Z88 you can simply call up the Calculator popdown using **R, even if you are in the middle of doing something else at the time:**

The top line of the calculator displays the result of your calculation - initially 0.00 - and below that are the calculator keys. You can press these in either of two ways, depending on your preference.

*Either:* Use the cursor keys , , to highlight the operation you want, and then press to enter the selected key.

*Or:* Type the Cambridge Z88 key corresponding to the key you want, as listed on the following table.

Calculator Key Legend: | Cambridge Z88 KeyEquivalent: | Function: |
---|---|---|

Clear | C | Clear |

DEL | Delete last keypress | |

StoM | S | Store to memory 0 to 9 |

RclM | R | Recall from memory 0 to 9 |

0 to 9 | 0 to 9 | Enter digit |

. | . | Decimal point |

Unit | U | Convert units (see below) |

Y<>x | Y | Swap y and x |

sIgn | I | Change sign |

Fix | F | Number of decimal places |

% | % | Percentage (see below) |

+ | + or P | Plus |

x | X, * or T | Times |

- | - or M
| Minus |

/ | /, \ or D | Divide |

= | = | Result |

## Entering numbers

Enter a number by selecting the digits with the cursor keys, and press ; or just type the number with the keys 0-9. You can use C or to correct typing mistakes. Numbers can contain a decimal point, obtained by typing the full-stop key, and can be entered in scientific notation, as in

1.27E6, entered as `1 . 2 7 E 6`

, which means 1.27 x 10^{6}.

7.1E-13, entered as `7 . 1 E 1 1 3`

, which means 7.1 x 10^{-13}.

The two operands of an operation can be exchanged, before pressing =, by selecting the Y<>x operation, or pressing `Y`

. For example, to find the reciprocal of a previous calculation, enter

`/ 1 Y =`

All calculations are performed to an accuracy of nine decimal places, and numbers can lie between 1E38 and 1E-38. The Calculator displays ** Error** if an error, such as 1/0, occurs.

## Display format

The format in which numbers are displayed can be altered with the *Fix* operation, which gives the prompt

`Fix?`

Typing a number between 0 and 8 will fix the number of decimal places displayed to the specified number; the initial value is 2. Typing 9 will give free format.

## Constants

Entering a number, followed by one of the arithmetic keys pressed twice, stores the operation as a constant operation and displays the operator with K at the top right-hand corner of the screen.

For example, entering

`1.15 * *`

sets up constant multiplication by 1.15, and displays `* K`

; entering

`1000 = `

then gives the result 1150.00, and

`2000 = `

gives the result 2300.00.

## Storing and Recalling

You can store a result for use later in a calculation with the StoM and RclM operations.

To store a result, select the StoM operation (or type S). The prompt

`StoM ?`

will be given, to which you should give a register number by typing a digit from 0 to 9. Up to ten different results can be stored, one in each register.

You can also add a result into a register, subtract a result from a register, multiply a register by a result, or divide a register by a result, by giving the StoM operation followed by '+', '-', '*', or '/' respectively, followed by the register 0 to 9.

You can cancel a store operation in the middle by pressing .

For example,

`1.2 S 9`

stores 1.2 in register 9, and

`3.56 S-9 `

subtracts 3.56 from the same register. Finally

`R 9 `

recalls the result from register 9.

## Percentages

The '%' key works in conjunction with one of the other keys '*', '/', '+', or '-' to calculate percentages, and to add or subtract a given percentage to or from a number. The following examples illustrate each of these cases.

To find 12% of 1500 enter

`1500 * 12 %`

To express 660/880 as a percentage, enter

`660 / 880 %`

To add 15% on to 125 enter

`125 * 15 % +`

Likewise, to discount 125 by 15% enter

`125 * 15 % -`

## Converting units

You can convert any result between the pairs of units displayed on the **CONVERT** menu by selecting the *Unit* operation.

Highlight the unit you want to convert to using the cursor keys, and press to perform the conversion. For example, to convert from Litres to Gallons highlight Gallons, and to convert from Gallons to Litres highlight Litres. To exit from the **CONVERT** menu press .