Calculating home expenses
The next worked example shows how to use the Cambridge Z88 to perform numerical calculations. It shows how you would analyse your monthly expenses, and discover what proportion of your income you were spending on each.
You will learn how to:
Enter numbers and expressions into a table
Copy expressions to save typing
Perform calculations
Alter the format of the numbers
Designing the table
You are going to create a table which shows for each of the months January to April what your expenditure has been on your rates, mortgage, food, car, gas and electricity.
At first sight it might appear that an awful lot of typing would be involved in setting up such a table. However, as you will see, all the repetition is carried out automatically for you by PipeDream and very little typing is actually needed.
Moving around the document
To set up the table of expenses you will need to be familiar with the procedure for moving the cursor between slots (or columns) in the document. Remember that you will need to use the following keys:
 symb_up.png |
| to move up a line |
symb_down.png |
| to move down a line |
| to move to the previous slot to the left | |
| to move to the next slot to the right | |
symb_diamond.png |
| to move to the left-most slot |
Also, when you are at the left-hand edge of a slot, pressing will move to the previous slot to the left, if there is one.
When you are working with a document you can use the First Column, Last Column, Top of Column, or Bottom of Column commands on the CURSOR menu to move to the four edges of the document in a single operation.
Labelling the table
You are now going to set up the column and row labels for the table of expenses.
Move the cursor to slot B1 and type the label Jan (for January). Likewise type Feb, March, and April in slots C1 to E1 to complete the column headings for the table. Later you could extend the table for a whole year's figures.
Now type the row labels for the different expense categories, as follows:
In slot: | Enter: |
|---|---|
A2 |
|
A3 |
|
A4 |
|
A5 |
|
A6 |
|
The table headings are now complete. Move the cursor back up to slot B2, and the table should appear as shown on the following screen:
Entering the rates
The rates in the example are going to be £500 per half-year. This is going to be divided evenly over each month's expenses, but you do not need to divide 500 by 6; PipeDream will do it for you. You only have to enter the expression 500/6 into slot B2 (the '/' sign means divide).
However, you first need to specify that this slot is to be an expression slot, so that whatever you type into it will be evaluated, and so that other slots on the table can refer to the result. To do this you give the Edit Expression command from the EDIT menu; alternatively you may find it more convenient to type X which has the same effect.
The slot B2 will be highlighted on the screen to show that you are editing an expression slot, and the cursor will move to the centre of the top line of the screen so that you can enter an expression. Type the expression
500/6
and press the
key to enter it into slot B2. The number 83.33 will be displayed right-aligned in slot B2.
Referring to slots
You do not need to type the rates expression into the other slots in row 2; you can simply indicate that you want the same value as slot B2 by typing the coordinates of that slot.
Move to slot C2 and press X to enter an expression. Then type
B2
and press
. The value 83.33 will appear in slot C2. Likewise enter the expression B2 into slots D2 and E2.
Effectively you have specified that you always want slots C2 to E2 to contain the same value as slot B2. So, for example, suppose you were granted a rates reduction to £400 per half-year. Move the cursor back to slot B2 and type X to display the slot's previous contents, 500/6. Delete them, by typing
D
and then type the new value:
400/6
Not only will the value in B2 change to 66.67, but slots C2 to E2 will also change, since they refer to this value.
Replicating values
Next you are going to enter the figure 200 for the four months' mortgage payments. Type 200 into slot B3. If you forgot to type X when entering the figure, the number will appear left-aligned just as you entered it. In this case, move the cursor back to the slot and press X and then