Creating a check and uncheck all function in Angular Js

I have few check boxes which I have been check already using ng-init

<div class="checkbox">
     <label>
      <input type="checkbox" ng-init="model.A='A'" ng-model="model.A" ng-true-value="'A'" ng-false-value="'nope'"/>A
     </label>
</div>
<div class="checkbox">
     <label>
      <input type="checkbox" ng-init="model.A='B'" ng-model="model.B" ng-true-value="'B'" ng-false-value="'nope'"/>B
     </label>
</div>
<div class="checkbox">
     <label>
      <input type="checkbox" ng-init="model.C='C'" ng-model="model.C" ng-true-value="'C'" ng-false-value="'nope'"/>C
     </label>
</div>

What I want is to create a function to make these check boxes check and uncheck when I check a seperate check box, link or a button. Can some one help me?

Its simple as below,

create a link to toggle the checkboxes check status, Here i have created three links

first one is for toggle the checkbox status, second one for uncheck all the checkboxes and last one for check all the checboxes.

<a href="#" ng-click="toggleCheck()">toggle check</a> | <a href="#" ng-click="uncheckAll()">uncheck all</a> | <a href="#" ng-click="checkAll()">check all</a>

click on uncheck will be handle like below,

$scope.uncheckAll = function() {
    $scope.model.A = false;
    $scope.model.B = false;
    $scope.model.C = false;
};

assign a value which result in uncheck of the checkboxes.

click on check all will be handle like below,

 $scope.checkAll = function() {
     $scope.model.A = 'A';
     $scope.model.B = 'B';
     $scope.model.C = 'C';
};

Assign the initial values that result in check status of the checkboxes.

Toggle check like below, if A unchecked then all gonna uncheck other vice all are gonna check.

$scope.toggleCheck = function() {
    if ($scope.model.A == false) {
        $scope.checkAll();
    } else {
        $scope.uncheckAll();
    }
};

here is a DEMO