Fortran输入/输出中*的目的是什么 [英] What is the purpose of * in Fortran input/output

问题描述

我正在学习 Fortran，因为嗯，是的，我认为我会学习它.但是，我完全没有发现 * 的用途在打印、阅读等方面的信息:

I am learning Fortran because well, yeah, thought I'd learn it. However, I've found utterly no information on what the purpose of * is in print, read, etc:

program main

    print *, "Hello, world!"

end program main

这个*的目的是什么?我做了一些研究，但我认为我没有正确理解它，我不想继续学习，直到我真正知道 * 的意义.

What is the purpose of this *? I've done some research however I don't think I understand it properly, I don't want to carry on learning until I actually know the point of *.

从我设法找到的内容来看，我认为它是某种格式说明符，但是，我不明白这意味着什么，我什至不知道我是否正确.我发现的所有教程都只是告诉我要写什么来打印到控制台，而不是 * 的实际含义.

From what I've managed to find I think that it's some sort of format specifier, however, I don't understand what that means and I have no idea if I'm even correct. All the tutorials I've found just tell me what to write to print to the console but not what * actually means.

推荐答案

你是对的，它是一个格式说明符.

You are correct in that it is a format specifier.

在 Wikibooks 上有一个页面与 IO 相关，并指出:

There's a page on Wikibooks to do with IO and that states:

第二个 * 指定用户希望读取数字的格式

The second * specifies the format the user wants the number read with

当谈到 read 语句时.这也适用于 write 和 print 语句.

when talking about the read statement. This applies to the write and print statements too.

对于定点实数:Fw.d;w 是分配给数字的空格总数，d 是小数位数.

For fixed point reals: Fw.d; w is the total number of spaces alloted for the number, and d is the number of decimal places.

他们给出的例子是

REAL :: A
READ(*,'(F5.2)') A

读取小数点前后两位的实数.因此，如果您要打印一个实数，您会使用:

which reads a real number with 2 digits before and after the decimal point. So if you were printing a real number you'd use:

PRINT '(F5.2)', A

得到四舍五入的输出.

在您的示例中，您只是打印文本，因此无需进行特殊格式设置.此外，如果您将格式说明符保留为 * 它会将默认格式应用于实数等.

In your example you're just printing text so there's no special formatting to do. Also if you leave the format specifier as * it will apply the default formatting to reals etc.

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