How to save application settings which can be accessible in all forms?

[tofighi]

I'm creating an application which should have Options form (dialog) and in this form I want to save some parameters such as some folder path, some configuration numbers,etc.
I want after saving the setting in the Options dialog, it saves it in the QSettings object and I'll be able to reload it when I need it.
How can I do this? and because these settings are important to all of other dialogs, I want to know the most efficient way to save these settings and also load it easily and also it will be accessible to all dialogs.
For example I have three forms:
MainWindow
Options
SomeDialog

folderPath1 = "c:/windows";
folderPath2 = "d:/programs";
size = 100;

I want to load Settings (folderPath1 , folderPath2 , size) in the start of program using MainWindow. Then I would like to be able to edit these settings via Options dialog.
In every point of program I would like to have access to these settings from SomeDialog.

Thanks in advance.

[ChrisW67]

QSettings, which you already identified, is a solution to this problem. What exactly is your difficulty?

[kosasker]

All about logic. You can find help about QSettings

you can write a function that loads your setting from an ini file. And call it from main form constructor.

For a ini file;

QString myinifilepath("myprogsettings.ini");
    QSettings myini(myinifilepath,QSettings::IniFormat);
    myini.beginGroup("Settings");
    if (myini.value("folderPath1").isValid())
    {
        ui->lineEdit1->setText(myini.value("folderPath1").toString());
    }
.....
.....
....
   myini.endGroup();

QString myinifilepath("myprogsettings.ini");
    QSettings myini(myinifilepath,QSettings::IniFormat);
    myini.beginGroup("Settings");
    if (myini.value("folderPath1").isValid())
    {
        ui->lineEdit1->setText(myini.value("folderPath1").toString());
    }
.....
.....
....
   myini.endGroup();

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if you want to save your settings, you can call a save function, which event you want.

myini.setValue("folderPath1",ui->lineEdit1->text());

myini.setValue("folderPath1",ui->lineEdit1->text());

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please read the docs and write little prototype applications to learn.