A、All of them are big but cheap. B、They are available on the Internet. C、We can buy them from a store. D、It takes hours to downl

The chances are you’ve been using apps for years. Your home or work computer has apps likes a spreadsheet program, calculator or photo editor. Recently these apps, or applications, evolved in a big way.
    Let’s start with platforms. You know, a place to put things. A table, in a basic sense, is a platform. You plug in some plates, cups and flatware and it turns into a great place to eat. Computers work the same way. They create platforms for software applications. A spreadsheet and an accounting app can turn a computer into a business tool. Music and video apps can make a computer a studio.
    For most of their history, apps have seemed big and expensive. [23]We often bought them at a store and loaded them onto a computer with a disk. And most of these apps didn’t connect to the Internet.
    Recently platforms have changed in big ways. Our mobile phones and tablets became useful platforms just like our computers and this enabled a different kind of apps. Instead of big expensive programs, many apps became smaller and cheaper. Instead of coming in a box or taking hours to download, [24]they could be purchased or downloaded for free from the Internet with a click even on the go. This made apps collectible.
    Now apps may wake you up in the morning, give you a snapshot of the news, play the music you like, help you get to the airport, check you in and help you read your new book, all from the palm of your hand. And these new apps have another advantage. Many are built to work with the Internet. This means they can back up your work, play your music, or connect you with friends, wherever you are — without opening a web browser.
    But it’s not just phones and tablets. Computers, browsers, social networks and gaming systems have all become platforms for a new generation of apps. [25]So apps aren’t really new. What have changed are platforms and marketplaces that make them easy to purchase and collect.
23. What were the apps like in the past?
24. What do we learn about the apps at the present time?
25. What makes the apps easy to purchase according to the talk?