Why reading and writing data is fundamental in MATLAB

Introduction

Reading and writing data lets your program get information from files and save results. This is how programs talk to the outside world.

You want to load a list of numbers from a file to analyze them.

You need to save your program's results so you can use them later.

You want to read text data like names or messages from a file.

You want to write logs to keep track of what your program did.

You want to share data between different programs or users.

Syntax

MATLAB

fileID = fopen('filename.ext', 'mode');
data = fread(fileID);
fclose(fileID);

fileID = fopen('filename.ext', 'mode');
fwrite(fileID, data);
fclose(fileID);

fopen opens a file. The 'mode' can be 'r' for reading or 'w' for writing.

fclose closes the file to save changes and free resources.

Examples

This reads all data from 'data.txt' as bytes.

MATLAB

fileID = fopen('data.txt', 'r');
data = fread(fileID);
fclose(fileID);

This writes the text 'Hello World' into 'output.txt'.

MATLAB

fileID = fopen('output.txt', 'w');
fwrite(fileID, 'Hello World');
fclose(fileID);

This reads the entire text file 'notes.txt' into a string variable.

MATLAB

data = fileread('notes.txt');

This writes a matrix of numbers into a CSV file.

MATLAB

writematrix([1 2 3; 4 5 6], 'numbers.csv');

Sample Program

This program writes a short message to a file, then reads it back and shows it on the screen.

MATLAB

filename = 'example.txt';

% Write some text to the file
fileID = fopen(filename, 'w');
fprintf(fileID, 'Hello, MATLAB!\nThis is a test file.');
fclose(fileID);

% Read the text back from the file
fileID = fopen(filename, 'r');
textData = fscanf(fileID, '%c');
fclose(fileID);

% Display the read text
fprintf('Content of the file:\n%s\n', textData);

Important Notes

Always close files after opening them to avoid errors and data loss.

Use the right mode ('r' for reading, 'w' for writing) to avoid overwriting or reading errors.

Reading and writing lets your program save work and use data from outside sources.

Summary

Reading and writing data connects your program to files and the outside world.

You use fopen, fread, fwrite, and fclose to handle files.

This lets you save results, load inputs, and share information easily.