Invoking an external command in Python is a two step process:

from subprocess import call
call(["ls","-1"])

I will begin our blog on Java Tutorial with an incredibly important aspect of java development:  memory management.  The importance of this topic should not be minimized as an application's performance and footprint size are at stake.

From the outset, the Java Virtual Machine (JVM) manages memory via a mechanism known as Garbage Collection (GC).  The Garbage collector

• Manages the heap memory.   All obects are stored on the heap; therefore, all objects are managed.  The keyword, new, allocates the requisite memory to instantiate an object and places the newly allocated memory on the heap.  This object is marked as live until it is no longer being reference.
• Deallocates or reclaims those objects that are no longer being referened. 
• Traditionally, employs a Mark and Sweep algorithm.  In the mark phase, the collector identifies which objects are still alive.  The sweep phase identifies objects that are no longer alive.
• Deallocates the memory of objects that are not marked as live.
• Is automatically run by the JVM and not explicitely called by the Java developer.  Unlike languages such as C++, the Java developer has no explict control over memory management.
• Does not manage the stack.  Local primitive types and local object references are not managed by the GC.

So if the Java developer has no control over memory management, why even worry about the GC?  It turns out that memory management is an integral part of an application's performance, all things being equal.  The more memory that is required for the application to run, the greater the likelihood that computational efficiency suffers. To that end, the developer has to take into account the amount of memory being allocated when writing code.  This translates into the amount of heap memory being consumed.

Memory is split into two types:  stack and heap.  Stack memory is memory set aside for a thread of execution e.g. a function.  When a function is called, a block of memory is reserved for those variables local to the function, provided that they are either a type of Java primitive or an object reference.  Upon runtime completion of the function call, the reserved memory block is now available for the next thread of execution.  Heap memory, on the otherhand, is dynamically allocated.  That is, there is no set pattern for allocating or deallocating this memory.  Therefore, keeping track or managing this type of memory is a complicated process. In Java, such memory is allocated when instantiating an object:

String s = new String();  // new operator being employed
String m = "A String";    /* object instantiated by the JVM and then being set to a value.  The JVM
calls the new operator */

When eCommerce companies want to optimize information security, password management tools enable users to create strong passwords for every login.

Better than a Master Pass
A two-factor authentication, a security process in which the user provides two means of identification, one of which is typically a physical token, such as a card, and the other of which is typically something memorized, such as a security code can drastically reduce online fraud such as identity theft . A common example of two-factor authenticationis a bank card: the card itself is the physical item and the personal identification number (PIN) is the data that goes with it.

LastPass 3.0 Premium and RoboForm, security downloads offer fingerprint-based authentication features that can be configured to any computer PC or mobile application.  Both are supported by the Google Authenticator mobile app for smart phone and device integration.

LastPass 3.0 is most powerful on-demand password manager on the market. LastPass 3.0 Premium includes mobile support and more features. Dashlane 2.0 is is not as robust, but includes a user-friendly interface. F-Secure Key is a free, one-device version of these top competitors. F-Secure Key is for exclusive use on an installed device, so password safe retention is dependent on proprietary use of the device itself. The application can be upgraded for a small annual fee.

Password Manager App Cross-Portability
F-Secure Key syncs with Mac, PC Android, and iOS devices simultaneously. A transient code is generated on mobile devices, in addition to the two-factor authentication default of the F-Secure Key master password security product.

Password capture and replay in case of lost credentials is made possible with a password manager. Integration of a password manager app with a browser allows a user to capture login credentials, and replay on revisit to a site. Dashlane, LastPass, Norton Identity Safe, Password Genie 4.0 offer continuous detection and management of password change events, automatically capturing credentials each time a new Web-based, service registration sign up is completed.

Other applications like F-Secure Key, KeePass, and My1login replay passwords via a bookmarklet, supported by any Java-equipped browser. KeePass ups the ante for would be keyloggers, with a unique replay technology.

Personal Data and Auto-Fill Forms
Most password managers fill username and password credentials into login forms automatically. Password managers also retain personal data for form fill interfaces with applications, and other HTML forms online. The RoboForm app is one of the most popular for its flexibility in multi-form password and personal data management, but the others also capture and reuse at least a portion of what has been entered in a form manually.

The 1Password app for Windows stores the most types of personal data for use to fill out forms. Dashlane, LastPass, and Password Genie store the various types of ID data used for form fill-in, like passport and driver's license numbers and other key details to HTML acknowledgement of discretionary password and personal information.

The Cost of Protection
LastPass Premium and Password Box are the lowest monthly password manager plans on the market, going for $1 a month. Annual plans offered by other password manager sources vary according to internal plan: Dashlane $20, F-Secure Key $16, and Password Genie, $15.
All password manager companies and their products may not be alike in the end.

Security checks on security products like password managers have become more sophisticated in response to product cross-portability and open source app interface volatility. Norton, RoboForm, KeePass, generate strong, random passwords on-demand. Some security procedures now require three-factor authentication, which involves possession of a physical token and a password, used in conjunction with biometricdata, such as finger-scanningor a voiceprint.

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Computer Programming as a Career?