diff --git a/src/core/Announcerment.ts b/src/core/Announcerment.ts
index b03c3bf..83e3ec5 100644
--- a/src/core/Announcerment.ts
+++ b/src/core/Announcerment.ts
@@ -242,7 +242,7 @@ namespace OS {
          */
         export var quota: 0;
         /**
-         * Place holder of all global events listeners
+         * Placeholder of all global events listeners
          */
         export var listeners: API.AnnouncerListenerType = {};
 
diff --git a/src/core/BaseApplication.ts b/src/core/BaseApplication.ts
index c9102e6..3eb0943 100644
--- a/src/core/BaseApplication.ts
+++ b/src/core/BaseApplication.ts
@@ -24,7 +24,7 @@ namespace OS {
      */
     export namespace application {
         /**
-         * Abstract prototype of all AntOS application.
+         * Abstract prototype of all AntOS applications.
          * Any new application definition should extend
          * this prototype
          *
@@ -97,7 +97,7 @@ namespace OS {
 
             /**
              * Init the application, this function is called when the
-             * application process is called and docked the the application
+             * application process is created and docked in the application
              * dock.
              *
              * The application UI will be rendered after the execution
@@ -380,7 +380,7 @@ namespace OS {
 
             /**
              * Base menu definition. This function
-             * return the based menu definition of all applications.
+             * returns the based menu definition of all applications.
              * Other application specific menu entries
              * should be defined in [[menu]] function
              *
diff --git a/src/core/BaseDialog.ts b/src/core/BaseDialog.ts
index 0b2deb3..89cd7a6 100644
--- a/src/core/BaseDialog.ts
+++ b/src/core/BaseDialog.ts
@@ -203,7 +203,7 @@ namespace OS {
             private markup: string | OS.API.VFS.BaseFileHandle;
 
             /**
-             * If the `markup` variable is not provided, the
+             * If the `markup` variable is not provided, then
              * the [[init]] function will find the scheme definition
              * in this class variable
              *
@@ -277,7 +277,7 @@ namespace OS {
              * Simple prompt dialog to get user input text.
              * The input date of the dialog:
              *
-             * ```
+             * ```typescript
              * {
              *      title: string, // window title
              *      label: string, // label text
@@ -458,7 +458,7 @@ namespace OS {
                  *
                  * Input data:
                  *
-                 * ```
+                 * ```typescript
                  * {
                  *      title: string // window title
                  * }
@@ -531,7 +531,7 @@ namespace OS {
              *
              * Input data:
              *
-             * ```
+             * ```typescript
              * {
              *      title: string // window title
              * }
@@ -610,7 +610,7 @@ namespace OS {
              *
              * Input data:
              *
-             * ```
+             * ```typescript
              * {
              *      title: string, // window title
              *      [propName:string]: any
@@ -689,7 +689,7 @@ namespace OS {
              *
              * Input data:
              *
-             * ```
+             * ```typescript
              * {
              *      title: string, // window title
              *      icon?: string, // label icon
@@ -771,7 +771,7 @@ namespace OS {
              *
              * Input data:
              *
-             * ```
+             * ```typescript
              * {
              *      title: string, // window title
              *      data:
@@ -941,7 +941,7 @@ namespace OS {
              *
              * Input data:
              *
-             * ```
+             * ```typescript
              * {
              *      title: string, // window title
              *      root?: string, // the root path folder of the file view
@@ -952,6 +952,15 @@ namespace OS {
              *
              * }
              * ```
+             * 
+             * Callback data:
+             * 
+             * ```typescript
+             * {
+             *      file: string, // selected file path
+             *      name: string // user input file name
+             * }
+             * ```
              *
              * @export
              * @class FileDialog
diff --git a/src/core/BaseService.ts b/src/core/BaseService.ts
index 61bf6f2..cf2b08e 100644
--- a/src/core/BaseService.ts
+++ b/src/core/BaseService.ts
@@ -18,7 +18,14 @@
 namespace OS {
     export namespace application {
         /**
+         * Services are processes that run in the background and
+         * are waken up in certain circumstances such as global
+         * events or user interactions.
          *
+         * Each service takes an entry in the system tray menu
+         * located on the system panel. This menu entry is used
+         * to access to service visual contents such as: options,
+         * task performing based on user interaction, etc.
          *
          * @export
          * @abstract
@@ -26,18 +33,70 @@ namespace OS {
          * @extends {BaseModel}
          */
         export abstract class BaseService extends BaseModel {
+            /**
+             * The service icon shown in the system tray
+             *
+             * @type {string}
+             * @memberof BaseService
+             */
             icon: string;
+
+            /**
+             * CSS class of the service icon shown in the system tray
+             *
+             * @type {string}
+             * @memberof BaseService
+             */
             iconclass: string;
+
+            /**
+             * Text of the service shown in the system tray
+             *
+             * @type {string}
+             * @memberof BaseService
+             */
             text: string;
+
+            /**
+             * Reference to the menu entry DOM element attached
+             * to the service
+             *
+             * @type {HTMLElement}
+             * @memberof BaseService
+             */
             domel: HTMLElement;
+
+            /**
+             * Reference to the timer that periodically execute the callback
+             * defined in [[watch]].
+             *
+             * @private
+             * @type {number}
+             * @memberof BaseService
+             */
             private timer: number;
+
+            /**
+             * Reference to th system tray menu
+             *
+             * @type {HTMLElement}
+             * @memberof BaseService
+             */
             holder: HTMLElement;
-            onmenuselect: (d: OS.GUI.TagEventType<GUI.tag.MenuEventData>) => void;
+
+            /**
+             * Place holder for service select callback
+             *
+             * @memberof BaseService
+             */
+            onmenuselect: (
+                d: OS.GUI.TagEventType<GUI.tag.MenuEventData>
+            ) => void;
 
             /**
              *Creates an instance of BaseService.
-             * @param {string} name
-             * @param {AppArgumentsType[]} args
+             * @param {string} name service class name
+             * @param {AppArgumentsType[]} args service arguments
              * @memberof BaseService
              */
             constructor(name: string, args: AppArgumentsType[]) {
@@ -53,25 +112,27 @@ namespace OS {
             }
 
             /**
-             *
+             * Do nothing
              *
              * @memberof BaseService
              */
             hide(): void {}
 
             /**
+             * Init the service before attaching it to
+             * the system tray: event subscribe, scheme
+             * loading.
              *
+             * Should be implemented by all subclasses
              *
              * @abstract
              * @memberof BaseService
              */
             abstract init(): void;
-            //implement by user
-            // event registe, etc
-            // scheme loader
 
             /**
-             *
+             * Refresh the service menu entry in the
+             * system tray
              *
              * @memberof BaseService
              */
@@ -80,7 +141,7 @@ namespace OS {
             }
 
             /**
-             *
+             * Get the service meta-data
              *
              * @returns {API.PackageMetaType}
              * @memberof BaseService
@@ -90,7 +151,8 @@ namespace OS {
             }
 
             /**
-             *
+             * Attach the service to a menu element
+             * such as the system tray menu
              *
              * @param {HTMLElement} h
              * @memberof BaseService
@@ -99,30 +161,35 @@ namespace OS {
                 this.holder = h;
             }
 
-            
             /**
+             * Set the callback that will be called periodically
+             * after a period of time.
              *
+             * Each service should only have at most one watcher
              *
              * @protected
-             * @param {number} t
-             * @param {() => void} f
+             * @param {number} t period time in seconds
+             * @param {() => void} f callback function
              * @returns {number}
              * @memberof BaseService
              */
             protected watch(t: number, f: () => void): number {
                 var func = () => {
                     f();
+                    if (this.timer) {
+                        clearTimeout(this.timer);
+                    }
                     return (this.timer = setTimeout(() => func(), t));
                 };
                 return func();
             }
 
-            
             /**
-             *
+             * This function is called when the service
+             * is exited
              *
              * @protected
-             * @param {BaseEvent} evt
+             * @param {BaseEvent} evt exit event
              * @returns
              * @memberof BaseService
              */
@@ -140,32 +207,34 @@ namespace OS {
             }
 
             /**
-             *
+             * Do nothing
              *
              * @memberof BaseService
              */
             main(): void {}
 
             /**
-             *
+             * Do nothing
              *
              * @memberof BaseService
              */
             show(): void {}
 
             /**
+             * Awake the service, this function is usually called when
+             * the system tray menu entry attached to the service is
+             * selected.
              *
+             * This function should be implemented by all subclasses
              *
              * @abstract
              * @param {GUI.TagEventType} e
              * @memberof BaseService
              */
             abstract awake(e: GUI.TagEventType<GUI.tag.MenuEventData>): void;
-            //implement by user to tart the service
-
 
             /**
-             *
+             * Do nothing
              *
              * @protected
              * @param {BaseEvent} evt
@@ -173,7 +242,7 @@ namespace OS {
              */
             protected cleanup(evt: BaseEvent) {}
         }
-        //implemeted by user
+
         BaseService.type = ModelType.Service;
         BaseService.singleton = true;
     }
diff --git a/src/core/core.ts b/src/core/core.ts
index e26ecc3..93464c3 100644
--- a/src/core/core.ts
+++ b/src/core/core.ts
@@ -17,39 +17,156 @@
 //along with this program. If not, see https://www.gnu.org/licenses/.
 
 "use strict";
+/**
+ * Reference to the global this
+ */
 const Ant = this;
 
 /**
- *
+ * Extend the String prototype with some API
+ * functions used by AntOS API
  *
  * @interface String
  */
 interface String {
+    /**
+     * Simple string hash function
+     *
+     * @returns {number}
+     * @memberof String
+     */
     hash(): number;
+
+    /**
+     * Parse the current string and convert it
+     * to an object of type [[Version]] if the string
+     * is in the format recognized by [[Version]],
+     * e.g.: `1.0.1-a`
+     *
+     * @returns {OS.Version}
+     * @memberof String
+     */
     __v(): OS.Version;
+
+    /**
+     * Convert the current string to base 64 string
+     *
+     * @returns {string}
+     * @memberof String
+     */
     asBase64(): string;
+
+    /**
+     * Unescape all escaped characters on the
+     * string using `\`
+     *
+     * @returns {string}
+     * @memberof String
+     */
     unescape(): string;
+
+    /**
+     * Convert the current string to uint8 array
+     *
+     * @returns {Uint8Array}
+     * @memberof String
+     */
     asUint8Array(): Uint8Array;
+
+    /**
+     * Format the current using input parameters.
+     * The current string should be a formatted string
+     * in the following form:
+     *
+     * ```typescript
+     * "example string: {0} and {1}".format("hello", "world")
+     * // return "example string: hello and world"
+     * ```
+     *
+     * @param {...any[]} args
+     * @returns {string}
+     * @memberof String
+     */
     format(...args: any[]): string;
+
+    /**
+     * Create a [[FormattedString]] object using the current
+     * string and the input parameters
+     *
+     * @param {...any[]} args
+     * @returns {OS.FormattedString}
+     * @memberof String
+     */
     f(...args: any[]): OS.FormattedString;
+
+    /**
+     * Check if the current string is translatable, if it
+     * is the case, translate the string to the language specified
+     * in the current system locale setting.
+     *
+     * A translatable string is a string in the following
+     * form: `"__(example string)"`
+     *
+     * @returns {string}
+     * @memberof String
+     */
     __(): string;
+
+    /**
+     * Translate current string to the language specified
+     * by the system locale setting
+     *
+     * @returns {string}
+     * @memberof String
+     */
     l(): string;
+
+    /**
+     * Trim left of a string by a mask string
+     *
+     * @param {string} arg specifies a sub-string to be removed
+     * @returns {string}
+     * @memberof String
+     */
     trimLeft(arg: string): string;
+
+    /**
+     * Trim right of a string by a mask string
+     *
+     * @param {string} arg specifies a sub-string to be removed
+     * @returns {string}
+     * @memberof String
+     */
     trimRight(arg: string): string;
+
+    /**
+     * Trim both left and right of a string by a mask string
+     *
+     * @param {string} arg specifies a sub-string to be removed
+     * @returns {string}
+     * @memberof String
+     */
     trimBy(arg: string): string;
 }
 
 /**
- *
+ * Extend the Data prototype with the
+ * [[timestamp]] function
  *
  * @interface Date
  */
 interface Date {
+    /**
+     * Return the timestamp of the current Date object
+     *
+     * @returns {number}
+     * @memberof Date
+     */
     timestamp(): number;
 }
 
 /**
- *
+ * Generic key-value pair object interface
  *
  * @interface GenericObject
  * @template T
@@ -59,7 +176,12 @@ interface GenericObject<T> {
 }
 
 /**
+ * Global function to create a [[FormattedString]] from
+ * a formatted string and a list of parameters. Example
  *
+ * ```typescript
+ * __("hello {0}", world) // return a FormattedString object
+ * ```
  *
  * @param {...any[]} args
  * @returns {(OS.FormattedString | string)}
@@ -67,21 +189,28 @@ interface GenericObject<T> {
 declare function __(...args: any[]): OS.FormattedString | string;
 
 /**
- *
+ * This global function allow chaining stack trace from one error to
+ * another. It is particular helping when tracking the source of
+ * the error in promises chain which results in some obfuscated stack
+ * traces as the stack resets on every new promise.
  *
  * @param {Error} e
  * @returns {Error}
  */
 declare function __e(e: Error): Error;
 
-//define the OS object
+/**
+ * This namespace is the main entry point of AntOS
+ * API
+ */
 namespace OS {
     /**
+     * Return an range of numbers
      *
-     *
-     * @param {number} left
-     * @param {number} right
-     * @param {boolean} inclusive
+     * @param {number} left start of the range
+     * @param {number} right end of the range
+     * @param {boolean} inclusive specifies whether the
+     * `right` of the range is included in the returned array
      * @returns {number[]}
      */
     function __range__(
@@ -114,7 +243,6 @@ namespace OS {
         );
     };
 
-    // chaning error
     Ant.__e = function (e: Error): Error {
         const reason = new Error(e.toString());
         reason.stack += "\nCaused By:\n" + e.stack;
@@ -122,14 +250,40 @@ namespace OS {
     };
 
     /**
-     *
+     * Represent a translatable formatted string
      *
      * @export
      * @class FormattedString
      */
     export class FormattedString {
+        /**
+         * Format string in the following form
+         *
+         * ```typescript
+         * "format string with {0} and {1}"
+         * // {[0-9]} is the format pattern
+         * ```
+         *
+         * @type {string}
+         * @memberof FormattedString
+         */
         fs: string;
+
+        /**
+         * The value of the format pattern represented
+         * in [[fs]]
+         *
+         * @type {any[]}
+         * @memberof FormattedString
+         */
         values: any[];
+
+        /**
+         * Creates an instance of FormattedString.
+         * @param {string} fs format string
+         * @param {any[]} args input values of the format patterns
+         * @memberof FormattedString
+         */
         constructor(fs: string, args: any[]) {
             this.fs = fs;
             this.values = [];
@@ -146,7 +300,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Convert FormattedString to String
          *
          * @returns {string}
          * @memberof FormattedString
@@ -156,7 +310,9 @@ namespace OS {
         }
 
         /**
-         *
+         * Translate the format string to the current system
+         * locale language, format the string with values and
+         * then converted it to normal `string`
          *
          * @returns {string}
          * @memberof FormattedString
@@ -174,7 +330,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Return the hash number of the formatted string
          *
          * @returns {number}
          * @memberof FormattedString
@@ -184,9 +340,10 @@ namespace OS {
         }
 
         /**
+         * Match the formatted string against a regular expression
+         * a string pattern
          *
-         *
-         * @param {(string | RegExp)} t
+         * @param {(string | RegExp)} t string or regular expression
          * @returns {RegExpMatchArray}
          * @memberof FormattedString
          */
@@ -195,7 +352,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Convert the formatted string to Base^$
          *
          * @returns {string}
          * @memberof FormattedString
@@ -205,7 +362,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Un escape the formatted string
          *
          * @returns {string}
          * @memberof FormattedString
@@ -215,7 +372,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Convert the formatted string to uint8 array
          *
          * @returns {Uint8Array}
          * @memberof FormattedString
@@ -225,7 +382,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Input values for the format string
          *
          * @param {...any[]} args
          * @memberof FormattedString
@@ -238,21 +395,70 @@ namespace OS {
     }
 
     /**
+     * This class represents the Version number format used by AntOS. A typical
+     * AntOS version number is in the following format:
      *
+     * ```
+     * [major_number].[minor_number].[patch]-[branch]
+     *
+     * e.g.: 1.2.3-r means that:
+     * - version major number is 1
+     * - version minor number is 2
+     * - patch version is 3
+     * - the current branch is release `r`
+     * ```
      *
      * @export
      * @class Version
      */
     export class Version {
+        /**
+         * The version string
+         *
+         * @type {string}
+         * @memberof Version
+         */
         string: string;
+
+        /**
+         * The current branch
+         * - 1: `a` - alpha branch
+         * - 2: `b` - beta branch
+         * - 3: `r` - release branch
+         *
+         * @private
+         * @type {number}
+         * @memberof Version
+         */
         private branch: number;
+
+        /**
+         * Version major number
+         *
+         * @type {number}
+         * @memberof Version
+         */
         major: number;
+
+        /**
+         * Version minor number
+         *
+         * @type {number}
+         * @memberof Version
+         */
         minor: number;
+
+        /**
+         * Version patch number
+         *
+         * @type {number}
+         * @memberof Version
+         */
         patch: number;
 
         /**
          *Creates an instance of Version.
-         * @param {string} string
+         * @param {string} string string represents the version
          * @memberof Version
          */
         constructor(string: string) {
@@ -288,10 +494,17 @@ namespace OS {
         }
 
         /**
+         * Compare the current version with another version.
          *
+         * The comparison priority is `branch>major>minor>patch`.
          *
-         * @param {(string | Version)} o
+         * For the branch, the priority is `r>b>a`
+         *
+         * @param {(string | Version)} o version string or object
          * @returns {(0 | 1 | -1)}
+         * Return 0 if the two versions are the same, 1 if
+         * the current version is newer than the input version,
+         * otherwise return -1
          * @memberof Version
          */
         compare(o: string | Version): 0 | 1 | -1 {
@@ -328,9 +541,10 @@ namespace OS {
         }
 
         /**
+         * Check if the current version is newer than
+         * the input version
          *
-         *
-         * @param {(string | Version)} o
+         * @param {(string | Version)} o version string or object
          * @returns {boolean}
          * @memberof Version
          */
@@ -339,9 +553,10 @@ namespace OS {
         }
 
         /**
+         * Check if the current version is older than
+         * the input version
          *
-         *
-         * @param {(string | Version)} o
+         * @param {(string | Version)} o version string or object
          * @returns {boolean}
          * @memberof Version
          */
@@ -350,7 +565,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Return itself
          *
          * @returns {Version}
          * @memberof Version
@@ -360,7 +575,7 @@ namespace OS {
         }
 
         /**
-         *
+         * Convert Version object to string
          *
          * @returns {string}
          * @memberof Version
@@ -496,25 +711,45 @@ namespace OS {
         return (this.getTime() / 1000) | 0;
     };
 
+    /**
+     * Variable represents the current AntOS version, it
+     * is an instance of [[Version]]
+     */
     export const VERSION: Version = "1.0.0-a".__v();
     /**
+     * Register a model prototype to the system namespace.
+     * There are two types of model to be registered, if the model
+     * is of type [[SubWindow]], its prototype will be registered
+     * in the [[dialogs]] namespace, otherwise, if the model type
+     * is [[Application]] or [[Service]], its prototype will be
+     * registered in the [[application]] namespace.
      *
+     * When a model is loaded in the system, its prototype is registered
+     * for later uses
      *
      * @export
-     * @param {string} name
-     * @param {*} x
+     * @param {string} name class name
+     * @param {*} x the corresponding class
      * @returns {*}
      */
-    export function register(name: string, x: PM.ProcessTypeClass): void {
+    export function register(name: string, x: PM.ModelTypeClass): void {
         if (((x as any) as typeof BaseModel).type === ModelType.SubWindow) {
-            GUI.dialog[name] = x;
+            GUI.dialogs[name] = x;
         } else {
             application[name] = x;
         }
     }
 
     /**
+     * This function cleans up the entire system and
+     * makes sure the system is in a new and clean session.
+     * It performs the following operations:
      *
+     * - Kill all running processes
+     * - Unregister all global events and reset the  global
+     * announcement system
+     * - Clear the current theme
+     * - Reset process manager and all system settings
      *
      * @export
      */
@@ -540,13 +775,15 @@ namespace OS {
     }
 
     /**
-     *
+     * Booting up AntOS. This function checks whether the user
+     * is successfully logged in, then call [[startAntOS]], otherwise
+     * it shows the login screen
      *
      * @export
      */
     export function boot(): void {
         //first login
-        console.log("Booting sytem");
+        console.log("Booting system");
         API.handle
             .auth()
             .then(function (d: API.RequestResult) {
@@ -562,10 +799,17 @@ namespace OS {
             .catch((e: Error) => console.error(e));
     }
 
+    /**
+     * Placeholder for all the callbacks that are called when the system
+     * exits. These callbacks are useful when an application or service wants
+     * to perform a particular task before shuting down the system
+     */
     export const cleanupHandles: { [index: string]: () => void } = {};
 
     /**
-     *
+     * Perform the system shutdown operation. This function calls all
+     * clean up handles in [[cleanupHandles]], then save the system setting
+     * before exiting
      *
      * @export
      */
@@ -585,11 +829,11 @@ namespace OS {
     }
 
     /**
-     *
+     * Register a callback to the system [[cleanupHandles]]
      *
      * @export
-     * @param {string} n
-     * @param {() => void} f
+     * @param {string} n callback string name
+     * @param {() => void} f the callback handle
      * @returns
      */
     export function onexit(n: string, f: () => void) {
@@ -597,7 +841,9 @@ namespace OS {
             return (cleanupHandles[n] = f);
         }
     }
-
+    /**
+     *
+     */
     export namespace API {
         /**
          *
diff --git a/src/core/handles/RemoteHandle.ts b/src/core/handles/RemoteHandle.ts
index 5c9487c..75c70e6 100644
--- a/src/core/handles/RemoteHandle.ts
+++ b/src/core/handles/RemoteHandle.ts
@@ -85,7 +85,7 @@ namespace OS {
          */
         export interface RequestResult {
             /**
-             * Indicate whether an the response is error
+             * Indicate whether the response is error
              *
              * @type {(boolean | string)}
              * @memberof RequestResult
diff --git a/src/core/pm.ts b/src/core/pm.ts
index a9359d2..67f10f7 100644
--- a/src/core/pm.ts
+++ b/src/core/pm.ts
@@ -1,7 +1,7 @@
 namespace OS {
     export namespace PM {
         export type ProcessType = application.BaseApplication | application.BaseService;
-        export type ProcessTypeClass = {
+        export type ModelTypeClass = {
             new <T extends BaseModel>(args: AppArgumentsType[]): T;
         };
         export var pidalloc: number = 0;
@@ -17,7 +17,7 @@ namespace OS {
          */
         export function createProcess(
             app: string,
-            cls: ProcessTypeClass,
+            cls: ModelTypeClass,
             args?: AppArgumentsType[]
         ): Promise<ProcessType> {
             return new Promise(function (resolve, reject) {