float型和double型的有关问题
float型和double型的问题
有段程序是这样的：
struct stu
{
int num;
char *name;
char sex;
float score;
} boy1={102,"Zhang ping",'M',78.5},*pstu;
main()
{
pstu=&boy1;
printf("Number=%d\nName=%s\n",boy1.num,boy1.name);
printf("Sex=%c\nScore=%f\n\n",boy1.sex,boy1.score);
printf("Number=%d\nName=%s\n",(*pstu).num,(*pstu).name);
printf("Sex=%c\nScore=%f\n\n",(*pstu).sex,(*pstu).score);
printf("Number=%d\nName=%s\n",pstu->num,pstu->name);
printf("Sex=%c\nScore=%f\n\n",pstu->sex,pstu->score);
}，运行正常，但是在我用double型替换float型后，如下，score项只显示0，这是为什么呢？
struct stu
{
int num;
char *name;
char sex;
double score;
} boy1 = { 102, "Zhang ping", 'M', 78.5 }, *pstu;
void main()
{
pstu = &boy1;
printf("Number=%d\nName=%s\n", boy1.num, boy1.name);
printf("Sex=%c\nScore=%d\n\n", boy1.sex, boy1.score);
printf("Number=%d\nName=%s\n", (*pstu).num, (*pstu).name);
printf("Sex=%c\nScore=%d\n\n", (*pstu).sex, (*pstu).score);
printf("Number=%d\nName=%s\n", pstu->num, pstu->name);
printf("Sex=%c\nScore=%d\n\n", pstu->sex, pstu->score);
}
------解决方案--------------------
The type character is the only required format field; it appears after optional format fields.
The type character determines whether the associated argument is interpreted as a character, string, or number.
The types C and S, and the behavior of c and s with printf functions, are Microsoft extensions and are not ANSI-compatible.
printf Type Field Characters
Character Type Output Format
c int or wint_t When used with printf functions, specifies a single-byte character.
C int or wint_t When used with printf functions, specifies a wide character.
d int Signed decimal integer.
i int Signed decimal integer.
o int Unsigned octal integer.
u int Unsigned decimal integer.
x int Unsigned hexadecimal integer, using "abcdef."
X int Unsigned hexadecimal integer, using "ABCDEF."
e double Signed value having the form [ – ]d.dddd e [sign]ddd where d is a single decimal digit, dddd is one or more decimal digits, ddd is exactly three decimal digits, and sign is + or –.
E double Identical to the e format except that E rather than e introduces the exponent.
f double Signed value having the form [ – ]dddd.dddd, where dddd is one or more decimal digits.
The number of digits before the decimal point depends on the magnitude of the number, and the number of digits after the decimal point depends on the requested precision.
g double Signed value printed in f or e format, whichever is more compact for the given value and precision.
The e format is used only when the exponent of the value is less than –4 or greater than or equal to the precision argument.
Trailing zeros are truncated, and the decimal point appears only if one or more digits follow it.
G double Identical to the g format, except that E, rather than e, introduces the exponent (where appropriate).
n Pointer to integer Number of characters successfully written so far to the stream or buffer; this value is stored in the integer whose address is given as the argument.
p Pointer to void Prints the address of the argument in hexadecimal digits.
s String When used with printf functions, specifies a single-byte–character string.
Characters are printed up to the first null character or until the precision value is reached.
S String When used with printf functions, specifies a wide-character string.
Characters are printed up to the first null character or until the precision value is reached.
有段程序是这样的：
struct stu
{
int num;
char *name;
char sex;
float score;
} boy1={102,"Zhang ping",'M',78.5},*pstu;
main()
{
pstu=&boy1;
printf("Number=%d\nName=%s\n",boy1.num,boy1.name);
printf("Sex=%c\nScore=%f\n\n",boy1.sex,boy1.score);
printf("Number=%d\nName=%s\n",(*pstu).num,(*pstu).name);
printf("Sex=%c\nScore=%f\n\n",(*pstu).sex,(*pstu).score);
printf("Number=%d\nName=%s\n",pstu->num,pstu->name);
printf("Sex=%c\nScore=%f\n\n",pstu->sex,pstu->score);
}，运行正常，但是在我用double型替换float型后，如下，score项只显示0，这是为什么呢？
struct stu
{
int num;
char *name;
char sex;
double score;
} boy1 = { 102, "Zhang ping", 'M', 78.5 }, *pstu;
void main()
{
pstu = &boy1;
printf("Number=%d\nName=%s\n", boy1.num, boy1.name);
printf("Sex=%c\nScore=%d\n\n", boy1.sex, boy1.score);
printf("Number=%d\nName=%s\n", (*pstu).num, (*pstu).name);
printf("Sex=%c\nScore=%d\n\n", (*pstu).sex, (*pstu).score);
printf("Number=%d\nName=%s\n", pstu->num, pstu->name);
printf("Sex=%c\nScore=%d\n\n", pstu->sex, pstu->score);
}
------解决方案--------------------
The type character is the only required format field; it appears after optional format fields.
The type character determines whether the associated argument is interpreted as a character, string, or number.
The types C and S, and the behavior of c and s with printf functions, are Microsoft extensions and are not ANSI-compatible.
printf Type Field Characters
Character Type Output Format
c int or wint_t When used with printf functions, specifies a single-byte character.
C int or wint_t When used with printf functions, specifies a wide character.
d int Signed decimal integer.
i int Signed decimal integer.
o int Unsigned octal integer.
u int Unsigned decimal integer.
x int Unsigned hexadecimal integer, using "abcdef."
X int Unsigned hexadecimal integer, using "ABCDEF."
e double Signed value having the form [ – ]d.dddd e [sign]ddd where d is a single decimal digit, dddd is one or more decimal digits, ddd is exactly three decimal digits, and sign is + or –.
E double Identical to the e format except that E rather than e introduces the exponent.
f double Signed value having the form [ – ]dddd.dddd, where dddd is one or more decimal digits.
The number of digits before the decimal point depends on the magnitude of the number, and the number of digits after the decimal point depends on the requested precision.
g double Signed value printed in f or e format, whichever is more compact for the given value and precision.
The e format is used only when the exponent of the value is less than –4 or greater than or equal to the precision argument.
Trailing zeros are truncated, and the decimal point appears only if one or more digits follow it.
G double Identical to the g format, except that E, rather than e, introduces the exponent (where appropriate).
n Pointer to integer Number of characters successfully written so far to the stream or buffer; this value is stored in the integer whose address is given as the argument.
p Pointer to void Prints the address of the argument in hexadecimal digits.
s String When used with printf functions, specifies a single-byte–character string.
Characters are printed up to the first null character or until the precision value is reached.
S String When used with printf functions, specifies a wide-character string.
Characters are printed up to the first null character or until the precision value is reached.