C language format input and output functions, format input and output functions

C language format input and output functions, format input and output functions

 

I. Format output function printf ()

1. The call format is printf ("format control string", output table column );

2. The formatting control string is used to specify the output format. It has three forms:

• 1. format description: Specifies the output format of the content of the corresponding output table column, starting with %, such as % d, % o, etc.
• 2. Escape Character: it is used to output the control code or special characters represented by escape characters, such as common '\ n' and' \ t'
• 3. common characters: the characters that need to be output as is.

3. The output table is listed as a number of data items to be output. It corresponds to the number and type of format specifiers;

4. The format character m specifies the width of the output data. n pairs of real numbers indicate the output n decimal places. + pairs represent the number of truncated characters in the string, indicating the right alignment, which is usually omitted.

-Left alignment. l is used for long integer data. It can be added before d, o, x, and u. More format specifiers and their combinations are as follows:

Format characters	Data Object	Output Format	Data Output Method
% (+)-Md	Int Unsigned int Short Unsigned short Char	Decimal integer	1. output by actual number of digits without m   2. m-bit output is available. If m-bit is exceeded, the output is based on the actual number of digits.   3. + (+ by default) right alignment (left space fill)   4. Align with-left (fill spaces on the right)
% (+)-Mo		Octal integer
% (+)-Mx		Hexadecimal integer
% (+)-Mu		Unsigned integer
% (+)-Mld	Long Unsigned long	Decimal integer
% (+)-Mlo		Octal integer
% (+)-Mlx		Hexadecimal integer
% (+)-Mlu		Unsigned integer
% (+)-M. nf	Float Double	Decimal decimal
% (+)-M. ne		Decimal Index
% (+)-G		The short output width in % f and % e is automatically selected for Single Output and double-precision floating point numbers.
% (+)-Mc	Char Int Short	Single Character	1. Output a single character without m 2. m-bit output with spaces filled 3. + (+ by default) right alignment (left space fill) 4. Align with-left (fill spaces on the right)
% (+)-M. ns	String	One string of characters	1. Output all characters based on the actual string without m and n 2. Only the first n characters are output for m and n, and spaces are supplemented. 3. There are + (+ by default) right alignment (left fill space) 4. Align with-left (fill spaces on the right)

 

 

 

 

Ii. format input function scanf ()

1. Call format: scanf ("format control string", address table column );

2. The formatting control string and printf () function have similar meanings. The difference is that they control the input format;

3. The address table contains memory unit addresses corresponding to a number of data waiting for input, which are separated by commas (,). Generally, the format is & a, and a is a variable;

4. The number and type of the address column correspond to the format specifiers in the format control string;

5. The format character h indicates the input short data. It can be used before d, o, and x, and m indicates the width of the input data,

* Indicates that the corresponding data item is not assigned to the corresponding variable after it is read. More format specifiers and their combinations are as follows:

Format characters	Data Object	Input Format	Data Input Method
% Md	Int Short Unsigned int Unsigned short	Decimal integer	1. Input by actual number of digits without m   2. m-bit input is available. If m-bit is not available, press Enter.
% Mo		Octal integer
% Mx		Hexadecimal integer
% Mld	Long Unsigned long	Decimal integer
% Mlo		Octal integer
% Mlx		Hexadecimal integer
% Mlf	Float Double	Decimal integer
% Mle
% Mc	Char	Single Character	1. Take a single character without m 2. m is input, which is only the first character.
% Ms	String	One string of characters	1. There are no characters before m to retrieve the car or space 2. m only takes the first m characters