SHEET.BBC is a simple spreadsheet program written in BBC BASIC.
When run, you are presented with a conventional matrix of rows
and columns.  With the evaluation version there are a maximum
of 5 columns and 12 rows, but with the full version there are
up to 7 columns and 999 rows.  The Page Up and Page Down keys
scroll up and down a screen at a time, the Home key moves to
the first row and the End key moves to the last row.

You can move around the spreadsheet using the cursor or Tab
keys, or you can click on a cell with the mouse; the current
cell is highlighted with a blue rectangle and its ID is shown
in the top left-hand corner (the column is indicated with a
letter A-G and the row with a number 1-999).  The contents of
the current cell are displayed on the top line, after the ID.

Row 'zero' of the spreadsheet is a special row which contains
formatting strings.  These determine how numbers are displayed
in that column, and also control the column width.  You can
'hide' a column by setting its width to zero (by making the
formatting string empty).  The formatting strings accord with
the specifications of the FNUSING.BBC library module (q.v.).

Spreadsheet cells, other than the special row 0, can contain
either character strings (which are displayed verbatim) or
numeric formulae (which are evaluated).  A formula cell is
indicated by the first character being an equals sign (=),
and can contain any valid BBC BASIC numeric expression.  A
formula can refer to the value in any other cell by means of
its alphanumeric ID, for example:

       =A3*B5

will calculate the product of the values in cells A3 and B5.
In addition to the usual numeric functions and operators, a
colon (:) signifies the sum of all the values in a specified
rectangle of cells.  For example:

       =A3:B5

will calculate the sum of the values in cells A3, A4, A5, B3,
B4 and B5.  You must not, either directly or indirectly,
reference the contents of the current cell.  If you do so,
the 'No Room' error will result.  Error messages are displayed
in the cell containing the erroneous data.

You can enter data into the current cell simply by typing it;
press the Enter key when the entry is complete.  Alternatively
you can edit the contents of the current cell by clicking with
the mouse in the top line.  The usual line editing features
are available.

The File menu allows you to load, save or print a spreadsheet,
to clear the spreadsheet or to exit the program.  Files are in
'comma-separated value' format, where the first line contains
the row zero formatting strings.  Cells may contain the comma
character (,) or the quotation mark character (") but NOT both.  
An example data file EXAMPLE.CSV is supplied.