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Learning diary 3- input and output of data

2022-07-20 08:33:00 【Astray King】

Character output function putchar

1.putchar()

2. Function return value ： Output characters

3. The functionality ： Display a character

Format output function printf

1.printf(" Format symbol ", Output variables );

2. Format symbol

Format symbol	effect
i,d	Decimal integer
x,X	Hexadecimal unsigned integer
o	Octal unsigned integer
u	An unsigned decimal integer
c	Single character
s	character string
e,E	character string
f	Floating point decimal in exponential form
g	e,f The shorter one
%%	The percent sign itself

3. Modifier

Modifier	function
m	The output data field is wide , Data length <m, Left padding ; Otherwise, press the actual output
.n	For real numbers , Specify the number of digits after the decimal point （ rounding ）; Specify the actual number of output bits for the string
-	The output data is left aligned in the field
+	Specifies that a positive sign is displayed before the positive number of signed numbers
0（ Numbers ）	When the output value is specified, the empty position not used on the left side will be filled in automatically 0
#	In octal and 16 Show leading before hexadecimal number 0,0x
l	stay d,o,x,u front , Specify the output precision as long type
	stay e,f,g front , Specify the output precision as double type

4. Escape character

Escape character	function
\b	Backspace , Move the current position to the previous column
\n	Line break , Moves the current position to the beginning of the next line
\t	Horizontal TAB （ Skip to the next tab Location ）
\r	enter , Move the current position to the beginning of the line
\"	Represents a double quotation mark
\\	Represents a backslash character ‘\’

Character input function getchar

1.getchar(); Read a character on the keyboard , When the returned value int type , Corresponding to a letter ascii value .

Format input function scanf

1.getchar Only one character data can be read from the keyboard , If you expect to read several data , And of any type , use scanf(" Format controller ", The input variable ); Be careful “%c” As a formatter , Spaces and escape characters can be entered as valid characters .

2. Modifier

Modifier	function
h	be used for d,o,x front , Specify input as short type
l	be used for d,o,x front , Designated as long type , be used for e,f, Designated as double type
m	Specify the input data width , End with a space or a non convertible character
*	Suppressor , Specify that the input item is not assigned to the variable after reading

3. When entering data , In case of space enter tab illegal input End of width All represent the end of data .