Data type - floating point (C language)

Catalog

1 Understand the representation and storage form of floating point numbers

1.1  Floating point classification

1.2  General representation of representation

1.3  Representation form — Exponential representation

 1.4  Floating point storage format

2 Floating point variables and constants

2.1  Floating point constants

2.2  Floating point variables

3 Comparison between floating-point numbers and zero values

3.1  Floating point number none “ zero ”

3.2  Floating point “ Zero value ” 

---

1 Understand the representation and storage form of floating point numbers

1.1  Floating point classification

C Language provides 3 There are specific floating-point types ：

（1）float- Single precision floating point

（2）double- Double precision floating point

（3）long double- Long double precision floating point

1.2  General representation of representation

（1） General notation ：[ Integral part ].[ Mantissa part ].

         The decimal point cannot be omitted , The integer part and mantissa part can be omitted , But you can't omit .

1.3  Representation form — Exponential representation

Index method : [ Sign bit ][ Mantissa part ]e[ Index part ].

Format requirements ：e And front must There are numbers ,e and E All are OK Index The part can be positive or negative or 0, but Must be an integer .

 1.4  Floating point storage format

  The storage format is divided into three parts ： Symbol part 、 mantissa Part and Index part .

2 Floating point variables and constants

2.1  Floating point constants

The default is double type , Such as ：3.5、4.0 And 3.5D、4.0d Equivalent .

Single precision constant , You need to explicitly add a suffix after the value f or F Such as 3.5f or 4.0F etc. .

2.2  Floating point variables

float f1=3.14F,f2;

f2=9.8f;

double d1;

d1=3.2; Equivalent to

d1=3.2d

3 Comparison between floating-point numbers and zero values

3.1  Floating point number none “ zero ”

3.2  Floating point “ Zero value ” 

Floating point numbers x And 0 Of The distance is less than or equal to the set value , I think x by “ zero ”

Illustrate with examples ：math.h in fabs Find the absolute value of floating point number

const float ESP=1E-6F;

fabs(x-0)<=ESP Represents a floating point type x by zero value .

Floating point numbers x And 0 Of The distance is less than or equal to the set value , I think x by “ zero ”