http://gru.stanford.edu/ 2026-05-14T19:38:13-0700 http://gru.stanford.edu/ http://gru.stanford.edu/lib/tpl/gru/images/favicon.ico text/html 2025-07-23T16:21:47-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/beta?rev=1753312907&do=diff mgl 2.0 Overview This beta version (mgl 2.0) contains cocoa based code for running under 64 bit Matlab on Mac OS X, a Windows alpha version (but not yet linux) and a number of improvements as outlined below. Everything in the mgl 2.0 beta for Mac text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/betaworkingnotes?rev=1661892024&do=diff MGL 2.0 Beta Working Notes Functions affected and status * mglPrivateOpen: working. * mglPrivateClose: working. * mglGetMouse: working. * mglGetKeyEvent: working. nanosecond time stamps. * mglGetMouseEvent: working. nanosecond time stamps. text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/camera?rev=1661892024&do=diff Compiling You will need the Spinnaker SDK. This works on MacOS but you need to follow directions in the README file that comes with it that tells you how to install the libraries it uses with homebrew. If everything works properly, you should be able to go to your Applications/Spinnaker/apps folder and run SpinView_QT. If you get the error text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/contributors?rev=1661892024&do=diff Contributors Design and Implementation * Justin Gardner (Mac OS X, OpenGL, sample programs, documentation, mgl/utils and mgl/task) * Jonas Larsson (Linux, OpenGL, Mac OS X and mgl/utils) Other contributors * Christopher Broussard (Mac OS X, Windows) * Denis Schluppeck (OpenGL and documentation) * Eli Merriam (OpenGL, EyeLink tracker interface) text/html 2023-12-07T09:26:09-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/dll?rev=1701969969&do=diff Issue: Library not loaded error It seems that we are getting error messages when running compiled Mex files that the dynamic link libraries cannot be resolved at runtime. The error looks like this: >> mglResolution Invalid MEX-file '/Users/justin/proj/mgl/mgllib/mglResolution.mexmaci64': dlopen(/Users/justin/proj/mgl/mgllib/mglResolution.mexmaci64, 0x0006): Library not loaded: @rpath/eyelink_core.framework/Versions/A/eyelink_core Referenced from: <C8BD6C3… text/html 2023-08-11T21:08:48-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/download?rev=1691813328&do=diff Download The latest version of mgl (3.0) can be retrieved using git: git clone https://github.com/justingardner/mgl.git mgl This version is compatible with MacOS Catalina (10.15) onwards as it is based on Metal and not OpenGL (which Apple no longer supports). If you need an older version of mgl, for example the earlier version that was based on OpenGL, you can get the version by switching to the v2_0 branch after you download: text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/exampletasks?rev=1661892024&do=diff Sample programs can be found in the /Task subfolder, and include: * taskTemplate (Stripped down version that contains only the functions you need to write a task. This is a good starting place for any new experiment you want to program). * taskTemplateContrast10bit text/html 2024-02-08T17:40:04-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/eyelink64bit?rev=1707442804&do=diff EyeLink 64bit library installation You may install directly from the SR Research website (you will need a login), see or if you are a GRU member you can download the files directly following the instructions below (note that the libraries are SR Research proprietary so we cannot distribute them to non-lab members). text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreference?rev=1661892024&do=diff Main screen functions mglOpen: Opens the screen usage: mglOpen(whichScreen, <screenWidth>, <screenHeight>, <frameRate>, <bitDepth>) purpose: Opens an openGL window argument value whichScreen 0=Window, 1=primary screen, 2=secondary screen, etc <screenWidth> text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencecoordinateframes?rev=1661892024&do=diff Functions to adjust the coordinate frame mglVisualAngleCoordinates: Visual angle coordinates purpose: Sets view transformation to correspond to visual angles (in degrees) given size and distance of display. Display must be open and have valid width and height (defined in MGL variable) text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencedemoprograms?rev=1661892024&do=diff Test/Demo programs Run these test programs without any parameters and they should display on your second monitor. With an optional single argument you can pass the number of the display you want to display on. * mglTestAlignment: Alignment of textures text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencedigio?rev=1661892024&do=diff Digital I/O Mgl has some functions to handle digital I/O with a National Instruments card (e.g. NI USB 6501) that can be used to read and write digital I/O signals and . These can be useful to synch to an MR scanner or control an external eye tracker. These functions all live in the directory: text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencedrawing?rev=1661892024&do=diff Drawing functions mglClearScreen purpose: sets the background color usage: mglClearScreen(<color>) argument value color color to set background to, can be a grayscale value or an [r g b] value set to the level of gray (0-1) mglClearScreen(gray) text/html 2024-07-15T14:53:22-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferenceeyelink?rev=1721080402&do=diff EyeLink Eyetracker functions Overview We have functions to interface Matlab with the EyeLink scanner. These functions allow you to calibrate the scanner and get current eye position information, etc. These are all referenced below. We have included 64-bit binaries based on a beta-version of Eyelink's frameworks. text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencegammatable?rev=1661892024&do=diff Gamma tables mglSetGammaTable: Sets the display card gamma table purpose: Set the gamma table usage: There are a number of ways of calling this function explained below. Setting a redMin, redMax, redGamma, greenMin, etc. mglSetGammaTable(0,1,0.8,0,1,0.9,0,1,0.75); text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferenceimages?rev=1661892024&do=diff Texture functions used for displaying images mglCreateTexture: Create a texture from a matrix purpose: Create a texture for display on the screen with mglBltTexture image can either be grayscale nxm, color nxmx3 or color+alpha nxmx4 usage: texture = mglCreateTexture(image,axis) text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencekeyboardandmouse?rev=1661892024&do=diff Keyboard and mouse functions mglDisplayCursor: Hide or display the mouse cursor purpose: Hide or display the mouse cursor usage: mglDisplayCursor(<display>) argument value display 1 or 0 to display or hide the cursor When you call mglOpen the mouse cursor is hidden by default. You can get it to come back by doing: text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencemovie?rev=1661892024&do=diff mglMovie availability: mgl 2.0 Mac OS X 64-bit Matlab only usage: movieStruct = mglMovie(filename,position) or mglMovie(movieStruct,command,<argument>); purpose: Used to display quicktime movies. (This *only* works on 64 bit Mac. There is some issue with the quicktime library QTKit and threads which does not seem to be a problem on 64 bit). You also need to be using a cocoa window, so make sure to set mglSetParam('movieMode',1) before running mglOpen. Check the sample experiment, taskTemplate… text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencescreen?rev=1661892024&do=diff Main screen functions mglOpen: Opens the screen usage: mglOpen(whichScreen, <screenWidth>, <screenHeight>, <frameRate>, <bitDepth>) purpose: Opens an openGL window argument value whichScreen 0=Window, 1=primary screen, 2=secondary screen, etc <screenWidth> text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencesound?rev=1661892024&do=diff Sound functions mglInstallSound: Install an .aiff file for playing with mglPlaySound purpose: Install an .aiff file for playing with mglPlaySound usage: mglInstallSound(soundName) argument value soundName aiff filename This will install sounds to be played using mglPlaySound. Note that if you just want to use systems sounds then you do not need to call this function directly, it will be called by mglOpen to install all your system sounds. Once the sound is installed you can play it with … text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencestencils?rev=1661892024&do=diff Stencils to control drawing only to specific parts of screen Here is a demonstration of how to use stencils using these these functions: mglOpen; mglScreenCoordinates;%Draw an oval stencil mglStencilCreateBegin(1); mglFillOval(300,400,[100 100]); mglStencilCreateEnd; mglClearScreen; text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencetext?rev=1661892024&do=diff Drawing text mglTextSet: Set parameters for drawing text purpose: Set text properties for mglText usage: mglTextSet(fontName,<fontSize>,<fontColor>,<fontVFlip>,<fontHFlip>,<fontRotation>,<fontBold>,<fontItalic>,<fontUnderline>,<fontStrikeThrough>) text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/functionreferencetiming?rev=1661892024&do=diff Timing functions mglGetSecs: Get time in seconds purpose: Get current or elapsed time usage: mglGetSecs(<t0>) argument value t0 start time from which to compute elapsed time To get current time t=mglGetSecs Get elapsed time since t0 t0 = mglGetSecs; elapsedTime=mglGetSecs(t0) text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/getting_started?rev=1661892024&do=diff MGL Getting Started text/html 2023-08-11T21:14:55-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/gettingstarted?rev=1691813695&do=diff Initial setup * Add the mgl directory to your Matlab path. In Matlab: >> addpath(genpath('MYPATH/mgl')); where MYPATH should be replaced by the path to your version of mgl. * Make sure to enable access for assistive devices so that you can use the function mglGetKeyEvent, mglGetMouseEvent, mglPostEvent, mglSimulateRun and mglEatKeys. text/html 2022-09-16T13:40:05-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/highbitdepth?rev=1663360805&do=diff High bit depth modes in mglMetal Often for luminance or contrast displays you need more than 8 bit color depth (for example, if contrast thresholds are under 1%, you need finer color resolution to show gratings). You can set color modes for higher bit depth with the following function: text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/knownissues?rev=1661892024&do=diff Resolved issues Check here for issues that have been resolved. Some issues may also be resolved in issues on github. Recompiling MGL We (Apple developers) run the latest Mac OS (10.10.2 as of 3/27/2015) with the latest version of Matlab (8.5) or (Linux developers) Ubuntu 64-bit (Gutsy) and 32-bit (Feisty) with Matlab 7.4 and the binaries are created to run on these systems. As noted above, some older versions (notably Matlab 14.1) are not able to use these mex files and crash when you try to… text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/mgl2p0?rev=1661892024&do=diff mgl 2.0 Overview This beta version (mgl 2.0) contains cocoa based code for running under 64 bit Matlab on Mac OS X, a Windows alpha version (but not yet linux) and a number of improvements as outlined below. Everything in the mgl 2.0 beta for Mac text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/mglcamera?rev=1661892024&do=diff mglCamera There are a few routines in mgl now that use the Spinnaker API. You may need to compile the binaries to get the library linkage working (also, for now this all is working in Matlab2015a and Mac OS Mavericks. A recent version of Mac OS is probably necessary for the Spinnaker text/html 2023-08-09T12:19:20-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/mglmetal?rev=1691608760&do=diff mglMetal (mgl version 3.0) Overview Metal is here! Cupertino has decided to bring more joy and happiness to the world by deprecating the widely used open standard OpenGL, thus making everyone's code obsolete. The ominous pronouncements have proved true, and OpenGL is no longer supported on MacOS versions after Catalina (like Big Sur and Monterey). These now require us to use Apple's proprietary standard Metal. As all the graphics in mgl was written with OpenGL using Cocoa frameworks (a variant… text/html 2023-08-31T15:30:54-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/mglmetalcoding?rev=1693521054&do=diff mglMetal Coding Conventions This page provides some background on coding conventions used in mglMetal Adding new commands If you want to add a new command, you will generally make an m file which will communicate with the mglMetal application using the mglSockets commands. Here is a basic template which just reads a integer value from the mglMetal application text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/mglsinglepage?rev=1661892024&do=diff MGL Mgl is a suite of mex/m files for displaying visual psychophysics stimuli and writing experimental programs in Matlab. Runs on Mac OS X (G4/5 and Intel 32 and Intel 64 bit OS Versions 10.5-10.7) Version 2.0. A quick overview mgl is a set of matlab functions for displaying full screen visual stimuli from matlab. It is based on OpenGL functions, but abstracts these into more simple functions that can be used to code various kinds of visual stimuli. It can be used on Mac text/html 2025-01-29T19:21:33-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/moncalib?rev=1738207293&do=diff Overview Moncalib is the program in MGL that we use to calibrate monitors. It is used to measure with a photometer (PhotoResearch, Minolta or Topcon) the monitor luminance values and then store them in a table that can be used by the initScreen function to make sure you always use a calibrated output. Moncalib talks through a serial interface to these photometers so that you don't have to sit and take each measurement. Depending on settings (how many repeats of each measurement and how finely … text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/niproblem?rev=1661892024&do=diff /System/Library/Extensions/NiViPciK.kext failed to load - (libkern/kext) not privileged; check the system/kernel logs for errors or try kextutil(8). text/html 2023-11-14T16:48:56-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/overview?rev=1700009336&do=diff MGL Mgl is a suite of mex/m files for displaying visual psychophysics stimuli and writing experimental programs in Matlab. Runs on Mac OS X and is compatible with latest versions of the Mac OS (Ventura as of this writing 8/11/2023). It is based on text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/pubs?rev=1661892024&do=diff How to cite mgl Please use our Zenodo based DOI for citing use of mgl in manuscripts: The Zenodo site has a tool for how to format for different journals, but here is an example: Gardner, JL, Merriam, EP, Schluppeck, D, & Larsson, J (2018) MGL: Visual psychophysics stimuli and experimental design package (Version 2.0) Zenodo text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/resolved_isses?rev=1661892024&do=diff MacOS Mojave Loss of keyboard and mouse events. This is resolved by going to System Preferences/Security & Privacy/Privacy/Accessibility and removing Terminal (uncheck) and then adding it back (check). Matlab 2016a In matlab 2016 there was a problem opening CGL screens (the default). This has been resolved by forcing open via cocoa by doing mglSetParam('useCGL',0) in mglOpen when it detects that Matlab 2016 or greater is being used. Also made some changes to mglPrivateOpen to handle opening o… text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreference?rev=1661892024&do=diff This page provides help for using MGL task structures to program experiments. You can also check out some examples. A quick overview The task structure can be used to help code experiments, it is completely separate from the basic mgl libarary that is used to display to the screen. text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferencecallbacks?rev=1661892024&do=diff Callbacks Callbacks are the way that you control what happens on different portions of the trial and what gets drawn to the screen. They are simply functions that get called at specific times in the experiment. It doesn't matter exactly what you call them, but it does matter exactly what order you register them in. text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferenceeyelink?rev=1661892024&do=diff Eyelink Overview You can use the Eyelink eye tracker with mgl and the task code. First, make sure that the mgl eyelink is compiled by following instructions here. * Using mglEditScreenParams select use of the Eyelink by setting eyeTrackerType to Eyelink. * Set parameters such as the number of calibration points you want to use, how far those calibration points are from the center of the screen, sample rate and what data you want to save, by using text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferenceeyetracking?rev=1661892024&do=diff Integrating eye tracking with a task There is a generic interface to the eye tracking functionality. As long as the appropriate callback functions are written for an eye tracker, no code needs to be changed in your task. To configure MGL to use an eye tracker you must initialize the eye tracker support. The eye tracker configuration is specified in the eyetracker field of myscreen. text/html 2022-08-30T13:40:24-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferencefunctionreference?rev=1661892024&do=diff Task function reference mglEditScreenParams availability: mgl 2.0 You can now use a GUI to set all of your screen parameters so that when you call initScreen everything is customized for your system. The settings will be stored across matlab sessions in a file called .mglScreenParams in your home directory. If you had been passing in a screenParams field to initScreen in your mgl program, you should convert to using mglEditScreenParams. To set the parameters you need to have mrTools installed… text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferencehowtos?rev=1661892025&do=diff How to cite use of mgl in a manuscript Please see here. How to end the experiment In general, the easiest way to code the stimulus is to have it continue indefinitely until the scanner stops scanning. After the scan is finished and you want to stop the stimulus you hit the ESC key. This way you never have the stimulus stop before the scanner does, and it doesn't hurt to keep having the stimulus go past the end of the scan. text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferenceoverview?rev=1661892025&do=diff A quick overview The task structure can be used to help code experiments, it is completely separate from the basic mgl libarary that is used to display to the screen (in that you do not have to use the task code to use the basic mgl functions). The structure for these experiments involves three main variables: text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferenceparameters?rev=1661892025&do=diff Experimental parameters Basics For your experiment you can choose what parameters you have and what values they can take on. You do this by adding parameters (of your choosing) into the parameter part of a task variable: task.parameter.myParameter1 = [1 3 5 10]; task.parameter.myParameter2 = [-1 1]; text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferencesavingdata?rev=1661892025&do=diff Saving data into a stimfile Stimfiles After you have run an experiment, all three variables (myscreen, task and your stimulus variable) will get saved into a file called yymmdd_stimnn.mat Where yymmdd is the current date, and nn is a sequential number starting at 01. This file will be stored in the current directory or in the directory ~/data if you have one. text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferencesegmenttimes?rev=1661892025&do=diff Segment times How to setup segment times Each trial can be divided into multiple segments where different things happen, like for instance you might have a stimulus segment and response segment that you want to have occur for 1.3 and 2.4 seconds respectively: text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/taskreferencesid?rev=1661892025&do=diff Subject ID Overview There is a set of functionality for keeping track of subjects and what experiments have been done. Basically, you can set parameters on an experiment computer to require that a subject ID is set and if so, the stimfile will get saved to a subject specific directory and a log will be saved that logs what experiments have been run (which can be used for reporting experiments and keeping track of what experiments have been run). text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/top?rev=1661892025&do=diff MGL * Overview * Download * Getting Started * Known Issues * Function Reference * Screen * Coordinate Frames * Images * Text * Drawing * Gamma Table * Stencils * Keyboard and Mouse * Timing * Sound * Movie * Digital I/O * EyeLink Eyetracker * Demo Programs * Task Reference * Overview * Parameters * Segment Times * Callbacks * Stimfiles * Eyetracking * How Tos * Function Reference * Eyelink * Example Tasks * Troubleshooting * Publicatio… text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/troubleshooting?rev=1661892025&do=diff When things don’t work, there are some very simple bugs you should check for before losing hope. Short segment lengths cause dropped frames Setting the length of the segments of a task to “0 second” can result in lots of dropped frames. This happens because mgl adjusts automatically for the difference between the expected ( text/html 2022-08-30T13:40:25-0700 Anonymous (anonymous@undisclosed.example.com) http://gru.stanford.edu/doku.php/mgl/workingwithc?rev=1661892025&do=diff Very brief guide to working with C The following section has been tested on: * macOS High Sierra (10.13.6), Matlab 2014b, XCode 10.1 * macOS Sierra (10.12.6), Matlab 2016b, Xcode 9.2 One might have to work with C to meddle with low-level codes for softwares, or for developing new programs. There are different kinds of files for C: