C中大写和小写双（浮点）类型说明符之间的区别

Question

在Cdouble/float中有一组类型说明符：%f%F%g%G%e%E。

有区别吗

%f 和 %F,
%g 和 %G,
%e 和 %E?

根据 printf 和 scanf 输出是相等的。那为什么大小写都有效呢？

请注意，scanf double 的类型说明符以小写字母开头 l

Answer 1

specifier   Output  Example
d or i  Signed decimal integer  392
u   Unsigned decimal integer    7235
o   Unsigned octal  610
x   Unsigned hexadecimal integer    7fa
X   Unsigned hexadecimal integer (uppercase)    7FA
f   Decimal floating point, lowercase   392.65
F   Decimal floating point, uppercase   392.65
e   Scientific notation (mantissa/exponent), lowercase  3.9265e+2
E   Scientific notation (mantissa/exponent), uppercase  3.9265E+2
g   Use the shortest representation: %e or %f   392.65
G   Use the shortest representation: %E or %F   392.65
a   Hexadecimal floating point, lowercase   -0xc.90fep-2
A   Hexadecimal floating point, uppercase   -0XC.90FEP-2
c   Character   a
s   String of characters    sample
p   Pointer address b8000000
n   Nothing printed.
The corresponding argument must be a pointer to a signed int.
The number of characters written so far is stored in the pointed location.  
%   A % followed by another % character will write a single % to the stream.    %

The Source of above

Answer 2

%f 和 %F 的区别在于它们将无穷大和 NaN 打印为小写还是大写。这是一个例子：

#include <stdio.h>
#include <math.h>

int main(){
    printf("%f and %f\n", INFINITY, nan("0"));    //Prints "inf and nan"
    printf("%F and %F\n", INFINITY, nan("0"));    //Prints "INF and NAN"
    return 0;
}

%f 和 %F 在打印实数时是相同的。例如，printf("%f", 1.0) 和 printf("%F", 1.0) 做完全相同的事情。

请注意 %F 仅适用于 C99 或 C++。

%e和%E的区别在于分隔数字和指数的"e"是小写还是大写（例如1.0e+0或1.0E+0。它对无穷大和 Nan 也有影响，就像 %f 和 %F 一样。这是一个例子：

#include <stdio.h>
#include <math.h>

int main(){
    printf("%e, %e and %e\n", INFINITY, nan("0"), 1.0); //Prints "inf, nan and 1.0000e+00"
    printf("%E, %E and %E\n", INFINITY, nan("0"), 1.0); //Prints "INF, NAN and 1.0000E+00"
    return 0;
}

%g和%G的区别在于%g取%e和%f之间最短的，%G取最短的%E 和 %F 之间最短。

C中大写和小写双（浮点）类型说明符之间的区别

Difference between upper and lower case double (float) type specifiers in C

c

types

double

format-specifiers