What is "half-width" number?

[hiverloon]

Can someone please tell me what this annoying "half-width number" is in the sentence below? My keyboard's button comes in full, none of them is cut in half.
電話番号の上5桁は半角数字でご入力ください。

 

[Mike Cash]

１２３４５６７８９０
1234567890

See?

Just input with your keyboard set to English layout and you'll be fine.

 

[hiverloon]

It's already in English layout since it's bought in my homecountry where roman alphabet is used.

 

[Mike Cash]

It's already in English layout since it's bought in my homecountry where roman alphabet is used.

If the numbers come out looking like my second line you're fine.

 

[hiverloon]

Never mind it's solved now, it turns out that the form I am filling in doesn't accept any space which was carried along during copy-pasting.

 

[komoto]

Here is half size - Full size Katakana converter.
You can convert them using this tools.
Language study tools : Full Size Katakana to Half Size Katakana Converter
Language study tools : Half Size Katakana to Full Size Katakana Converter

 

[Mike Cash]

You can convert them using this tools.

He reported the problem solved last November.