”あっ” ... Why a small つ？(Lesson 2.4)

こんにちは、みなさん。

In Lesson 2.4 there is the statement:

あっ、タクシー が き ました。

What's the function of the small つ in this instance being placed after the あ?  Are there other places this occurs that are worth knowing about?

Using the Japanese IME keyboard for Windows, how do I type a small つ when I'm not placing any letters after it?

ありがとうございます。

Each mora (like あ) in the syllabery is one beat so the "small tsu" would give an extended "beat" (or sustain), indicating that the word is pronounced like "ah" instead of "a".

I'm on a mac, but I think the keystroke is the same to compose half-width kana like ょ (よ), ゅ (ゆ), っ (つ). Type 'x' or 'l' followed by the mora, so "xtsu" (or ltsu)  gives っ, "xyo" (lyo) gives ょ, etc.

こんにちは (Konnichiwa) JohnB232 and toru e,

Thank you for your question! 

There are a couple of different ways we can use this small っ.

Like toru e says, the first way we can use っ is to create a double consonant sound. You can use it in this way when you see two consonants next to each other, like “TT” or “KK." When you see this little っ in the middle of a word like  がっこう (gakkō) "school," it creates a double consonant sound, where the sound before the consonant is held for a second. In the case of がっこう (gakkō), the "k" sound is held. 

However, when we use っ at the end of a word, it has a slightly different effect! 

At the end of a word, っ works similarly to an exclamation mark: to show emotions like surprise or anger.
あっ (A) is exactly the same as あ (a), but by using a little っ at the end, you can add a little more emotion. It also cuts the sound a little shorter.  

Remember, when っ is used in the middle of a word, it is showing a double consonant, and when it is used at the end of the word, it is showing emotion: just like an exclamation mark!

I've added the link to our brand new lesson on Japanese pronunciation, just incase you wanted to read a little more about っ. 
↓
https://members.rocketlanguages.com/members/japanese/lessons/4996/1-6-Pronouncing-Japanese

I hope this helped! Please let me know if you have any more questions!

べんきょう　を　がんばって　ください！ (Benkyō o ganbatte kudasai!)