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1-2-3 Notes
All Versions
September 6, 1984
Lotus Development Corporation
NOTE 102
Memory Use
Introduction
A 1-2-3 worksheet has 256 columns and 2,048 rows (or 523,288
cells), but the actual amount of information you can enter on one
worksheet depends on the amount of available memory. Available
memory depends on four factors:
* the amount of Random Access Memory (RAM) in the computer
* the organization of the worksheet
* the type of data you are entering
* the amount of information you enter in each cell
This note examines some basic aspects of 1-2-3 and memory use.
Random Access Memory
Random Access Memory, or RAM, is the amount of temporary memory
available in the computer. The memory is temporary because
information is stored in RAM only when the computer is turned on.
If you turn the computer off, all the information in RAM is lost.
(To permanently store information, you save it on a floppy disk or
hard disk.)
RAM is measured in bytes. One kilobyte, or 1K, is equal to 1,024
bytes. If a computer has 256K, it has 256 kilobytes (or 262,144
bytes) of RAM.
Think of RAM as spaces in the computer for storing information
while you are working. The larger the RAM, the more bytes, or
spaces, are available for use with a worksheet.
The /Worksheet Status Command
The /Worksheet Status command displays information about the
worksheet settings and the amount of available memory on a
worksheet. Begin with a new 1-2-3 worksheet on the screen and
select the /Worksheet Status command.
The headings for the worksheet settings and available memory
appear at the top of the screen. The third line displays the
status of the settings and memory. The number under Avail Memory
is the amount of RAM (in bytes) available for use with the
worksheet. (This is not the available space on the disk.)
On a new worksheet, the Avail Memory status reflects the amount of
RAM in the computer minus the memory used by 1-2-3 and the
operating system. The available memory will vary depending on
which version of 1-2-3 you are using, the size of the operating
system, and the particular drivers you have installed. 1-2-3
requires approximately 100K, and the operating system may need
from 12K to 30K depending on the system. The remaining memory is
available for a worksheet, and the amount of available memory will
decrease as you enter information on the worksheet.
Note: 1-2-3 does not support the use of the Assign command in
DOS. If you have used DOS's Assign command, the available
memory status may be over several megabytes.
If you add memory to the computer, the increase will automatically
be reflected by an increased amount of memory available for the
worksheet. The amount of memory you can add varies from computer
to computer.
Worksheet Organization and Memory Use
The way information is organized on a worksheet helps determine
how much memory is needed. 1-2-3 defines the "active worksheet
area" as a rectangle extending from cell A1 to the last column and
row where information was entered or a cell was formatted. You
can identify this active area by pressing the End key followed by
the Home key. This moves the pointer to the cell in the
lower-right corner of the active area.
It is important to know the size of the active area because 1-2-3
allocates 4 bytes of memory for every blank cell that falls within
the active area of the worksheet. For example, if you entered
information in cell T20, 1-2-3 would define the active area as the
range from A1 to T20. Memory would be allocated for that range
even though you entered information in only one cell. If you
pressed the End key followed by the Home key, the pointer would go
to cell T20.
Since blank cells in the active area take up memory, you should
make the active area of the worksheet as compact and close to A1
as possible.
Note: If you are creating a worksheet containing a macro, keep in
mind that blank rows and columns between the macro and the
worksheet use up memory. Although you should enter a macro
in a blank area of the worksheet, choose a spot that will
keep the active area of the worksheet as small as possible.
Using End-Home to Evaluate the Active Area
The following exercise uses the End and Home keys to examine the
relationship between worksheet size, organization, and memory use.
1. Start with an empty worksheet. Move the pointer to any cell
but do not enter any information. To check the End-Home
position, press the End key and then the Home key. The
pointer should move to cell A1 because you have not entered
any information on the worksheet.
2. Select /Worksheet Status. Look under Avail Memory and write
down the number of bytes available on the empty worksheet.
Press the Return key to return to Ready Mode.
3. Go to cell E1 and enter a single letter. Move the pointer
back to cell A1. Now press the End and Home keys. The
pointer should move to cell E1 because 1-2-3 has defined the
active area of the worksheet as the range from A1 to E1.
4. Select /Worksheet Status again and look at the available
memory. 1-2-3 has used 4 bytes for every empty cell in the
active area between cells A1 and E1. Write down how much
memory is now available. Press Return.
5. Go to cell A10 and enter a single letter. Press the End and
Home keys, and the pointer should move to cell E10. Remember,
1-2-3 defines the active area as a rectangle extending from
cell A1 to the last column and row where information was
entered. 1-2-3 now defines the active area as the range from
A1 to E10.
6. Select /Worksheet Status again and look at the available
memory. Compare the number under Avail Memory to the other
two numbers you wrote down. 1-2-3 has used 4 bytes for every
blank cell in the active area between cells A1 and E10. Press
the Return key to return to Ready Mode.
Using /File Xtract to Adjust the Active Area
Sometimes the End-Home position is not where you expect it to be.
If you have placed and then erased information or accidently typed
a character in a remote cell, the End-Home position may be far
from the worksheet data and you may get a Memory Full error
message. Memory Full means there is no more memory (RAM)
available for use with the worksheet. Erasing the contents of a
cell does not change the active area of the worksheet, so erasing
a cell or even deleting several rows will not increase the
available memory.
To decrease the active area of a worksheet and regain memory, use
the /File Xtract command. /File Xtract copies all of the
information in a specified range of the worksheet to a separate,
new worksheet file. The active area of this new worksheet file
includes only the range of information you copied.
Note: If you are doing a /File Xtract on a worksheet, be sure to
include all the information you want copied into the new
file. Also, choose a new file name. If you choose an
existing file name, the worksheet you are extracting will
replace the existing file. See the 1-2-3 User's Manual for
more information on /File Xtract.
1. Start with a new worksheet and enter the following
information, beginning in cell A1:
A B C
1 1984 Jan. Feb.
2 Rent 550 550
3 Food 400 350
4 Car 180 40
5 Medical 65 0
2. Press the End and Home keys. The pointer should move to cell
C5. Select /Worksheet Status and write down the amount of
available memory.
3. Go to cell E10 and enter a number or letter. Go back to cell
A1 and press the End and Home keys to identify the active area
of the worksheet. Select /Worksheet Status and write down the
amount of available memory.
4. Go to cell E10 and use the /Range Erase command to erase the
information there. Move back to cell A1 and press End and
Home again. Even though you erased the information in cell
E10, 1-2-3 remembers that information was placed there and
does not change the active area of the worksheet. Select
/Worksheet Status. You will see you have not regained any
memory by erasing cell E10.
5. Move the pointer to cell A1 and select /File Xtract. Select
Formulas.
6. Type in a new file name. Name the new file Memory for this
example. Press Return.
7. Now specify the worksheet range that you want to extract into
the new file, Memory. The range should include only cells
with relevant information (A1 to C5 in this example). Do not
include the blank cells below or to the right of the worksheet
data.
8. Press Return, and 1-2-3 will extract the range you specified
and make a new worksheet file.
9. To see the new file, select /File Retrieve and choose the file
named Memory. Check the size of the active area of the new
file by pressing End and Home. The End-Home position should
be cell C5. Select /Worksheet Status and check the available
memory. It should be greater than the amount of memory you
recorded before extracting the file.
Worksheet Content and Memory Use
The amount of information you can enter on a worksheet depends on
the content of the cells as well as the organization of the data.
The following information should help you evaluate memory use in a
worksheet:
* Blank cells use 4 bytes.
* Integers (numbers between -32768 and 32768) use 4 bytes.
* Real numbers use 12 bytes.
* Labels up to 4 characters long use 6 bytes. Longer labels use
an additional byte for each additional character. For example,
a 3-character label would use 6 bytes, and a 10-character label
would use 12 bytes.
* Formulas use a minimum of 30 bytes. The more complex a
formula, the more memory it uses.
* Range names use 32 bytes each, regardless of the length of the
name.
* Graph names use 461 bytes each, regardless of which options are
used.