C Language-printf function

printf function

1) Basic Concepts

The printf function is a library function provided by C's compiled system to output content to the output buffer

Specific stdio.h – header file for standard input (scanf) output (printf)

printf ("xxxx");/scanf ("%d", &a);

2) Use

Format: printf ("format-controlled string", variable list);

int a,b,c;

A = b = c = 10;

printf ("a =%d,b =%d,c =%d", a,b,c);

Note: How many placeholders are in the format-controlled string, and the number of variables that follow the list of variables

3) Problem with Format control (placeholder)

%d outputs an integer variable value (default is 10 binary)

%f real Type (single and double precision)

%lf

%c character type

%s String type

%x outputs the variable in 16 binary form

%o Output in 8-binary form

(1) When the output is added modifier

*)%MD m indicates the number of bits (domain width)

%5d

<m is a positive number;:

If the actual number of bits to be output is > m, output this number as-is

Actual Mantissa < M, left to fill empty (replenishment worth)

int a=2000;//number of digits =4

Prinf ("A=%3d", a);-->|2000|

Prinf ("a=%5d", a);-->| 2000|

<m is negative;:

If the actual number of bits to be output is > m, output this number as-is

Actual Mantissa < M, right fill empty

int a=2000;//number of digits =4

Prinf ("A=%3d", a);-->|2000|

Prinf ("a=%5d", a);-->|2000 |

* *)%0MD m represents the number of digits--this use can also

0 indicates the content of the complement

for (int i=0;i<81;i++) {

NSString *str = [NSString stringwithformat:@ "xxxx_%02d.jpg", I];

}

Xxxx_00.jpg

Xxxx_01.jpg

....

Xxxx_10.jpg

%f output a real-type data

The default is six digits after the decimal point (six digits after the decimal point, does not mean that the valid number is the latter six bit,

0.123456--six digits after the decimal point are valid digits

10.123456--only 5 digits after the decimal point is valid, the 6th bit of output may be garbled, 10.123450,10.12345x)

(1)%m.nf

m represents the total number of digits, if the number of bits (m is positive, left padding blank, otherwise right padding)

M is can be omitted%.2f reserved decimal 2 digits (common)

n indicates the number of digits after the decimal point

(2)%f accuracy problem

Data of type float has 7 valid digits by default. However, after the decimal point, the default six-bit, that is,->3.000000;

Double doubles the default number of 16 digits that are valid. However, after the decimal point, the default six-bit, that is,->3.000000;

C Language-printf function