A language choice must be made using the %language directive prior to using GENERATE or GENERATE_TYPE Main program

In MATLAB, the `%language` directive is used to specify the programming language you want to use for generating code in a particular block of code within your main program. This feature allows you to mix different languages when working with Simulink models that involve multiple blocks or custom components, where one might require C/C++, SystemC, or another supported language for better performance, low-level control, or hardware interaction.

Here's a brief explanation:

1. `%language C`: If you place this directive at the beginning of a section, all subsequent `GENERATE` or `GENERATE_TYPE` commands in that block will generate C code instead of defaulting to MATLAB code. This is useful when you want to leverage the speed and efficiency of compiled code for specific parts of your model.

2. `%language SystemC`: For SystemC modeling, you can switch to SystemC-based code generation, which is particularly relevant if you need to work with event-driven simulations or hardware interfaces.

Example usage:

% Set the language to C for a specific block or function
% Replace 'myBlock' with the actual name of your block
model = open_system('myModel');
set_param(model,'/myBlock','Language','C');

% Generate C code from a specified type or function
% For instance, if you have a function called 'customFunction'
% You would write: 
% generate_code(fullfile(model.Path,'customFunction.m'),'c')