C language | printf output function

C The concept of language output

The output is based on the computer host , The output of data from a computer to an output device is called output ,C The language itself does not contain output statements , If you don't add headers , The following code will report an error .

//#include<stdio.h>// The header file  
int main()// The main function   Program entry  
{
   printf("Hello xiaolin!\n");// \n It means new line  
   return 0;
}

Compilation result ：

D:\ Yan Xiaolin \ Handout materials \1-100\ test .cpp In function 'int main()':
D:\ Yan Xiaolin \ Handout materials \1-100\ test .cpp [Error] 'printf' was not declared in this scope

C Language printf usage

1、 General format

printf（ Format control , Output table columns ）

• Format control

Format control is a string enclosed in double quotation marks , call “ Conversion control string ”, abbreviation “ Format string ”, contain ：

• Format statement ： from % And format characters , Such as %d、%f.
• Ordinary character ： That is, the characters that need to be output as they are .

• Output table columns
  • The output table column is some data that the program needs to output , It can be a constant 、 Variable or expression .

C Language format characters

1、d Format symbol

Used to output a signed decimal integer .

2、c Format symbol

Used to output a character

3、s Format symbol

Used to output a string

4、f Format symbol

Used to output real numbers , Output in decimal form , There are two uses ：

① Basic type , use %f, Do not specify the length of the output data , According to the actual situation of the data, the system determines the number of columns occupied by the data .

② Specify the data width and scale , use %m.nf,m The data representing the output occupies m That's ok ,n It means that it contains n Decimal place .

③ The output data is aligned to the left , use %-m.nf, Function and ② almost , That's the data to the left , Fill in the space at the right end .

5、e Format symbol

Used to specify that real numbers are output exponentially .

C Language format characters	significance
d	Output a decimal integer by symbol
c	Output a character
s	Output a string
f	Output real numbers in decimal form
%m.nf	m Specify the data width ,n Specify the number of decimal places
e	Output real numbers in exponential form
l	And d The format is the same , Used to d Format symbol
o	Output as octal integer
x	Output as a hexadecimal number
u	Output unsigned decimal integer data
g	Output floating point number , The system selects automatically f or e Format symbol

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