MATLAB Programming

6 Data Import and Export
One MATLAB process (running send.m) writes a message to the file via its
memory map. It also writes the length ofthemessagetobyte1inthefile,
which serves as a means of notifying the other process that a message is
available. The second process (running answer.m) monitors byte 1 and, upon
seeing it set, displays the received message, puts it into uppercase, and echoes
the message back to the sender.
The send Function
This function prompts you to enter a string and then, using memory-mapping,
passes the string to another instance of MATLAB that is running the answer
function.
Copy the send and answer functions to files send.m and answer.m in your
current working directory. Begin the demonstration by calling send with no
inputs. Next, start a second MATLAB session on the same machine, and call
the answer function in this session. To exit, press Enter.
function send
% Interactively send a message to ANSWER using memmapfile class.
filename = fullfile(tempdir, 'talk_answer.dat');
% Create the communications file if it is not already there.
if ~exist(filename, 'file')
[f, msg] = fopen(filename, 'wb');
if f ~= -1
fwrite(f, zeros(1,256), 'uint8');
fclose(f);
else
error('MATLAB:demo:send:cannotOpenFile', ...
'Cannot open file "%s": %s.', filename, msg);
end
end
% Memory map the file.
m = memmapfile(filename, 'Writable', true, 'Format', 'uint8');
while true
% Set first byte to zero, indicating a message is not
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