Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Memory management across languages

From: Foundations of Programming: Fundamentals

Video: Memory management across languages

There's one thing we haven't talked about so far in any detail, and that's memory. Well, that's really because in JavaScript, we don't have to talk about it. We create our variables and our objects, we use them, and we forget about them. But this isn't always the case. In several languages, you can't just create an object, use it, and forget about it. You have to manage the memory that, that object uses, manage the lifetime of that object. If I was to show you some pseudo code examples, it would be that instead of just creating an object, we first have to manually allocate an area of memory.

Memory management across languages

There's one thing we haven't talked about so far in any detail, and that's memory. Well, that's really because in JavaScript, we don't have to talk about it. We create our variables and our objects, we use them, and we forget about them. But this isn't always the case. In several languages, you can't just create an object, use it, and forget about it. You have to manage the memory that, that object uses, manage the lifetime of that object. If I was to show you some pseudo code examples, it would be that instead of just creating an object, we first have to manually allocate an area of memory.

We have to grab hold of a piece of RAM and say, "I am going to use this." Then we can create our object and we can point it to that area of memory. We say, "That's what you are using. That's where your data is being stored." We use that reference what's called a pointer to that object and just use the object, call its methods, access its properties. But at some point what we are going to have to do is realize that we are not using it anymore. We don't need that memory, so we free the memory. It doesn't sound too hard, but when you start passing around these objects, you start calling functions, you start having a long lived program, this can get quite difficult.

A very common mistake is this. We allocate some memory, we then create an object, we start using that object, and then nothing. We actually don't need the object anymore, but we forgot to free the memory, or we thought we were freeing it, but we didn't free it probably. Well, that gives us a memory leak. Not a problem if you only do this once, but if you have a long-lived program that creates thousands of objects, as our program runs, it's going to get slower and slower and take up more and more memory, and at some point may even crash because of it.

But the memory leak isn't the only problem we can have. If, for example, we go back to our first object where we've already freed up that memory, well there might still be a variable that's actually pointing to that area of memory. It's what's called a pointer. And if we try and use that variable because we think the object still exists but it doesn't, we have what's called a dangling pointer, and that can actually cause our program to crash. And because memory management is difficult code to write, what's happened is as more high-level languages have evolved, there's been different methods for dealing with it.

If you remember early on in the course, we talked about the idea of low-level to high-level languages. The languages like assembly language and C were actually quite close to the machine code. You had to know a lot about how the machine operated, whereas things like Java, C#, and VB.NET were further away, you didn't have to think about that as much. Well, memory management is one of those areas. If you're working with assembly language, and C, you have to do a lot of manual work to allocate and free areas of memory that you're using.

As you start to get into the more modern high-level languages, there are techniques for dealing with it. Objective-C and C++ can choose to use something called reference counting. This is preferable to manual memory management and it allows us to keep a counter of who is using the object, but rather than manually free the memory, we just allow the system to free it up when it realizes that counter has reached 0. If we move into languages like Java, C#, and VB.NET, there is a memory management technique called garbage collection.

Rather than keep track of individual objects, what happens is the system itself keeps track of how much memory your application is using. And at certain times in your program's lifetime, what it's going to do is scan through all your objects and figure out which ones are still relevant, which ones are still being used. So it might take a sweep through a thousand objects, clear up 500 of them, and leave 500 of them around. It's called garbage collection because it bashes this up. It doesn't happen all the time.

In fact, you can't even guarantee when it will happen. When you're dealing with these languages, sometimes as a programmer, you can kind of suggest to the garbage collector that it might be a good time to go and clear up areas of memory, but you don't have to work on the individual level of the individual objects. And further up, when you get into more scripting languages, it's really fully automatic. You have either no or next to no control over when memory will be reclaimed. Now, you might think well, the automatic one sound great. The issue is of course that the more automatic it is, usually the slower it is, the less efficient it is.

Because while writing manual memory management code is tedious, it's difficult to do, if you can do it right, it leads to the most efficient use of memory, and if that's your goal, then you might be looking at languages that allow you to do manual memory management. However, for productivity, and particularly because we're in a world where we really don't have to worry about memory quite as much as we used to going back a couple of decades, you will find that the higher level languages using things like garbage collection, they usually win for being able to create code and create programs faster.

Show transcript

This video is part of

Image for Foundations of Programming: Fundamentals
Foundations of Programming: Fundamentals

61 video lessons · 85490 viewers

Simon Allardice
Author

 
Expand all | Collapse all
  1. 4m 14s
    1. Welcome
      1m 16s
    2. Making the most of this course
      2m 8s
    3. Using the exercise files
      50s
  2. 22m 11s
    1. What is programming?
      5m 45s
    2. What is a programming language?
      4m 48s
    3. Writing source code
      5m 34s
    4. Compiled and interpreted languages
      6m 4s
  3. 16m 29s
    1. Why JavaScript?
      4m 45s
    2. Creating your first program in JavaScript
      6m 54s
    3. Requesting input
      4m 50s
  4. 31m 38s
    1. Introduction to variables and data types
      5m 16s
    2. Understanding strong, weak, and duck-typed languages
      3m 51s
    3. Working with numbers
      5m 4s
    4. Using characters and strings
      4m 5s
    5. Working with operators
      4m 47s
    6. Properly using white space
      6m 46s
    7. Adding comments to code for human understanding
      1m 49s
  5. 24m 49s
    1. Building with the if statement
      7m 35s
    2. Working with complex conditions
      4m 10s
    3. Setting comparison operators
      6m 59s
    4. Using the switch statement
      6m 5s
  6. 17m 56s
    1. Breaking your code apart
      4m 1s
    2. Creating and calling functions
      2m 57s
    3. Setting parameters and arguments
      6m 7s
    4. Understanding variable scope
      2m 23s
    5. Splitting code into different files
      2m 28s
  7. 13m 32s
    1. Introduction to iteration
      4m 28s
    2. Writing a while statement
      5m 24s
    3. Creating a for loop
      3m 40s
  8. 19m 28s
    1. Cleaning up with string concatenation
      4m 30s
    2. Finding patterns in strings
      8m 3s
    3. Introduction to regular expressions
      6m 55s
  9. 19m 59s
    1. Working with arrays
      5m 47s
    2. Array behavior
      5m 29s
    3. Iterating through collections
      5m 18s
    4. Collections in other languages
      3m 25s
  10. 10m 50s
    1. Programming style
      5m 55s
    2. Writing pseudocode
      4m 55s
  11. 25m 55s
    1. Input/output and persistence
      3m 6s
    2. Reading and writing from the DOM
      8m 11s
    3. Event driven programming
      7m 47s
    4. Introduction to file I/O
      6m 51s
  12. 24m 26s
    1. Introduction to debugging
      5m 57s
    2. Tracing through a section of code
      7m 5s
    3. Understanding error messages
      3m 21s
    4. Using debuggers
      8m 3s
  13. 14m 17s
    1. Introduction to object-oriented languages
      5m 18s
    2. Using classes and objects
      6m 29s
    3. Reviewing object-oriented languages
      2m 30s
  14. 11m 14s
    1. Memory management across languages
      5m 11s
    2. Introduction to algorithms
      4m 2s
    3. Introduction to multithreading
      2m 1s
  15. 29m 20s
    1. Introduction to languages
      1m 42s
    2. C-based languages
      4m 40s
    3. The Java world
      3m 13s
    4. .NET languages: C# and Visual Basic .NET
      6m 17s
    5. Ruby
      3m 4s
    6. Python
      2m 56s
    7. Objective-C
      4m 3s
    8. Libraries and frameworks
      3m 25s
  16. 1m 2s
    1. Where to go from here
      1m 2s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ.

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Join now "Already a member? Log in

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Foundations of Programming: Fundamentals.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferencesfrom the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Are you sure you want to delete this note?

No

Your file was successfully uploaded.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.