any one help me how to explain this code

function varargout = gui(varargin)
% GUI MATLAB code for gui.fig
%      GUI, by itself, creates a new GUI or raises the existing
%      singleton*.
%
%      H = GUI returns the handle to a new GUI or the handle to
%      the existing singleton*.
%
%      GUI('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in GUI.M with the given input arguments.
%
%      GUI('Property','Value',...) creates a new GUI or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before gui_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to gui_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help gui

% Last Modified by GUIDE v2.5 15-Apr-2015 02:44:11

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @gui_OpeningFcn, ...
                   'gui_OutputFcn',  @gui_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT

% --- Executes just before gui is made visible.
function gui_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to gui (see VARARGIN)

% Choose default command line output for gui
handles.output = hObject;
ports = getAvailableComPort();

handles.s=serial(ports(1),'BaudRate',9600);
handles.s.RequestToSend = 'off';
handles.s.DataTerminalReady = 'off';
handles.s.BytesAvailableFcn = {@mycallback,hObject};
% Initialize slider and its readout text field
buffSize = 60;
circBuff = nan(1,buffSize);
x = 1:60; % Make up some data and plot
% Create a surface plot of peaks data. Store handle to it.
handles.plot1 = plot(handles.axes1,x,circBuff);
handles.plot2 = plot(handles.axes2,x,circBuff);
handles.plot3 = plot(handles.axes3,x,circBuff);

set(handles.com,'String',[' ';getAvailableComPort()])
set(handles.warning, 'String','Normal','BackgroundColor','Green')
% Update handles structure
guidata(hObject, handles);

% UIWAIT makes gui wait for user response (see UIRESUME)
% uiwait(handles.figure1);

% --- Outputs from this function are returned to the command line.
function varargout = gui_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;

% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
if strcmp(get(handles.s, 'Status'), 'closed')
    disp "opened"
    fopen(handles.s);
end

% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
if strcmp(get(handles.s, 'Status'), 'open')
    disp "closed"
    fclose(handles.s);
end

% --- Executes on selection change in com.
function com_Callback(hObject, eventdata, handles)
% hObject    handle to com (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: contents = cellstr(get(hObject,'String')) returns com contents as cell array
%        contents{get(hObject,'Value')} returns selected item from com
str = (get(hObject,'String'));
val = get(hObject,'Value');
temp = char(str(val));
set(handles.s,'Port',temp);

% --- Executes during object creation, after setting all properties.
function com_CreateFcn(hObject, eventdata, empty)
% hObject    handle to com (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: popupmenu controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end

function warning_Callback(hObject, eventdata, empty)
% hObject    handle to warning (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of warning as text
%        str2double(get(hObject,'String')) returns contents of warning as a double

% --- Executes during object creation, after setting all properties.
function warning_CreateFcn(hObject, eventdata, empty)
% hObject    handle to warning (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end

function mycallback(obj,eventdata,hfigure)
    %BytesAvailable = obj.BytesAvailable;
    data = fread(obj, obj.BytesAvailable);
    if data(1,1)==112 && data(end,1)==10
        temp1 = find(data==112);
        temp2 = find(data==116);
        temp3 = find(data==102);
        temp4 = find(data==13);
        pressure = (data(temp1+1,1)-48)*10^(temp2-temp1-2)+(data(temp1+2,1)-48)*10^(temp2-temp1-3)+((data(temp1+3,1)-48)*10^(temp2-temp1-4))*(temp2-temp1-3)
        temperature = (data(temp2+1,1)-48)*10^(temp3-temp2-2)+((data(temp2+2,1)-48)*10^(temp3-temp2-3))*(temp3-temp2-2)+((data(temp2+3,1)-48)*10^(temp3-temp2-4))*(temp3-temp2-3)
        fluidrate = (data(temp3+1,1)-48)*10^(temp4-temp3-2)+(data(temp3+2,1)-48)*10^(temp4-temp3-3)+((data(temp3+3,1)-48)*10^(temp4-temp3-4))*(temp4-temp3-3)
    end
    handles = guidata(hfigure);
    circBuff = get(handles.plot1,'YData');
    circBuff = [circBuff(2:end) pressure];
    set(handles.plot1,'YData',circBuff);

      circBuff = get(handles.plot2,'YData');
      circBuff = [circBuff(2:end) temperature];
      set(handles.plot2,'YData',circBuff);

      circBuff = get(handles.plot3,'YData');
      circBuff = [circBuff(2:end) fluidrate];
      set(handles.plot3,'YData',circBuff); 

      newdata = [pressure, temperature, fluidrate];
      stats = get(handles.tab, 'Data');
      stats = [newdata; stats(1:end-1,:)];
      set(handles.tab, 'Data', stats);

      if ((pressure<=290)&&(pressure>=270)) && ((temperature<=40)&&(temperature>=10)) && ((fluidrate<=110)&&(fluidrate>=100))
          set(handles.warning, 'String','Normal','BackgroundColor','Green')
      elseif ((pressure>260) && (pressure< 270)) ||  ((pressure>290) && (pressure< 300)) || ((temperature>40) && (temperature< 50)) || ((temperature>0) && (temperature<10)) || ((fluidrate>110) && (fluidrate< 120)) || ((fluidrate>90) && (fluidrate<100))
          set(handles.warning, 'String','Safety Limit','BackgroundColor','Yellow')
      else
          set(handles.warning, 'String','Warning','BackgroundColor','Red')
      end

% --- Executes when user attempts to close figure1.
function figure1_CloseRequestFcn(hObject, eventdata, handles)
% hObject    handle to figure1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
if strcmp(get(handles.s, 'Status'), 'open')
    fclose(handles.s);
end
 delete(handles.s)
% Hint: delete(hObject) closes the figure
delete(hObject);

[Jan]

You post a large program in an unreadable form and expect that anybody takes hours to explain all little details?

The question is far to general to be answered seriously.

Answer 1

[Walter Roberson]

What about it? It manages a list of serial ports and reads and plots pressure, temperature, and fluid readings read from the serial port. It keeps the last 60 points plotted.