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:

 to move up a line 
 to move down a line 

 to move to the previous slot to the left 

 to move to the next slot to the right 

 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:

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


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


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


and then type the new value:


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  afterwards.

You do not need to type the same value in slots C3 to E3; the Replicate command will do it automatically.

Select the Replicate command from the BLOCKS menu, and press  to execute it. Answer the prompts as follows, pressing  to move to the next line after entering B3:

Range to copy from
Range to copy to
C3 E3

This says that you are going to replicate the value in slot B3 to the range of slots C3 to E3. Press  to give the command, and the figure 200.00 should appear across the entire row so that the table appears as shown:


Note that until you press the  key you can alter the values you have typed for the ranges, moving between the two prompts with and .


Other expenses

The expenses in the other categories will tend to vary each month. You can either type in the figures used in the example shown below, or use figures from your own experience. In either case complete the table, remembering to make each slot into an expression slot before you enter the figure, or if you forget, afterwards.


Monthly totals

You are now going to produce monthly totals for the expenses. Enter the label TOTAL into slot A7, and press  to move the cursor to slot B7.

Now press X, and enter the following expression:

sum(B2 B6)

Press the  key, and PipeDream will perform the calculation and instantly display the sum of the figures in the range of slots B2 to B6; ie all the expenses for January.

The function sum(B2 B6) is a convenient way of writing the equivalent expression


where the slots to be added are all in a row, column, or rectangular table.


Replicating slot references

Just as you replicated the value 200.00 above, you can also replicate an expression across a range of slots. Where the expression contains references to other slots, as in this example sum(B2 B6), the references will automatically be altered to reflect the change in position.

Replicate the expression you have just entered for slot B7 to slots C7 to E7 as follows. Select the Replicate command from the BLOCKS menu, and give the options as:

Range to copy from
Range to copy to
C7 E7

Press  and totals will appear for each column. The Replicate command has automatically altered the range B2B6 to give the appropriate totals in columns C to E.

If you now move the cursor to slot C7 you will see the expression in that slot displayed at the top left-hand side of the screen:


Note that PipeDream removes unnecessary spaces when storing an expression.


Percentage expenditures

As a final illustration of the power of PipeDream in analysing figures, you are going to calculate the percentage expenditure represented by each of the categories in the table.

First type the label


in slot Fl.

Next find the total expenditure for the four months in the table. Move to slot F7, press X, and enter the expression

sum(B7 E7)

Instead of typing the references B7 and E7, you can 'point to' each slot by moving the highlighted slot with the keys  and  ,   and , and then give the Insert Reference command, K, to enter the corresponding references, B7 and then E7, into the editing line.

Now move to F2 and enter the following expression (which will be explained in a moment):

sum(B2 E2)/$F$7 * 100

Press  to enter the expression.

This expression is built up as follows:

sum(B2 E2) is the total spent on rates for the four months.

F7 is the overall total expenditure for the four months. The $ signs 'freeze' the reference so that when the expression is replicated, the reference to F7 will remain the same.

sum(B2 E2)/$F$7 is thus the proportion of the overall expenditure spent on rates.

sum(B2 E2)/$F$7 * 100 expresses this proportion as a percentage.

Now replicate this expression down the remaining slots in column F by giving the Replicate command from the BLOCKS menu, and entering the options as

Range to copy from
Range to copy to
F3 F6

The appropriate percentages will be displayed against each category.


Changing the format

When you first start using PipeDream, the results of all expression slots are displayed with two decimal places, the most useful format for working with financial calculations (although values are stored internally with full accuracy).

You can alter the display format for all expression slots in your document by changing the Decimal Places option on the Options Page menu, or for individual slots with the Decimal Places command on the LAYOUT menu.

For example, the table would look tidier if the percentages were displayed with no decimal places. First, mark the block of slots containing the percentages with the following procedure:

  1. Move the cursor to F2 and give the Mark Block command on the BLOCKS menu; alternatively, type Z as shown on the list of key functions above the keyboard.
  2. Move the cursor to F6 and give the Mark Block command again.

The block containing slots F2 to F6 will now be highlighted.

Now select the Decimal Places command from the LAYOUT menu. Reply to the prompts as follows:

Number of decimal places
Floating format

Press  and the numbers will be displayed with no decimal places.

You can also specify that certain characters, given on the Options Page, should be displayed before or after certain numbers in the document. By default, the trailing characters are set to '%', and the leading characters are set to '£'.

To display a '%' sign after the numbers in the marked block, give the Trailing Characters command from the LAYOUT menu.

You can also display a '£' sign before each value in the table. Mark the block of slots from B2 to E7 by moving the cursor to each of these slots in turn and typing Z. Then give the Leading Characters command from the LAYOUT menu.

Finally, the column labels can be right-aligned. Mark slots B1 to F1 with the Mark Block command, Z, and give the Right Align command from the LAYOUT menu.

Press Q to clear the marked area, and the table will now appear as shown:


What you have learnt

These three examples have demonstrated how PipeDream can help you to write letters and design text documents (word processing), set up lists of information, sort them, retrieve the items you need (databases), and set up and perform calculations on tables of numerical or financial information (spreadsheets).

For simplicity, each example focussed on one aspect of PipeDream's capabilities. However, the real power of PipeDream comes in its ability to mix all three different functions in a single document. For example, the expense account could be incorporated into a letter to your bank manager, the name and address list could include financial information and calculations, or the party invitation could be automatically addressed to everyone on your name and address list.

You are now in a position to start using PipeDream for your own applications, but to get the most out of its facilities you will probably want to read through the list of commands given in Section Five. You will then be able to refer back to it when your requirements of PipeDream become more advanced.

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