C + + format string description

C + + formatted strings are often used as output for formatted numbers, string merges and transformations, and many more.

1. Formatting the specified character

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symbolic effect

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%d decimal signed integer

%u decimal unsigned integer

%f floating point

%s string

%c Single character

%p The value of the pointer

floating-point numbers in the form of%e indices

%x,%x unsigned integer in hexadecimal notation

%0 unsigned integer represented in octal

%g automatic selection of appropriate representations

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Description:

(1). You can insert a number between "%" and a letter to indicate the maximum field width.

For example:%3d represents the output of 3 -bit integers, not enough 3 -bit right-justified.

The%9.2f represents a floating-point number with an output field width of 9, where the decimal bit is 2 and the integer bit is 6.

one decimal point, not enough 9 -bit right-aligned.

The%8s represents the output of a 8 -character string, which is not aligns aligned to 8 characters.

if the length of a string, or the number of integers exceeds the width of the description, it is output at its actual length. But for floating-point numbers, if the integer number of bits exceeds the width of the indicated integer digits, it will be output according to the actual integer digits; if the fractional number of digits exceeds the indicated decimal width, the output is rounded by the width of the description.

In addition, if you want to add some 0 before the output value, you should add a 0 before the field width.

For example ,%04d means that when you output a value that is less than 4 bits, it will be preceded by 0 to make its total width 4 bits.

If you use floating-point numbers to represent the output format of a character or integer, the number after the decimal point represents the maximum width, and the number before the decimal point represents the minimum width.

For example,%6.9s indicates that a string with a length of not less than 6 and not greater than 9 is displayed . If it is greater than 9, the contents of the 9th character will be deleted.

(2). You can add a lowercase letter L between "%" and the letter, indicating that the output is a long form.

For example,%ld indicates an output long integer

%LF indicates the output double floating-point number

(3). You can control the output left or right alignment, that is, "%" and the letter by adding a "-" sign to indicate that the output is left-justified, otherwise it is right-justified.

Example:%-7d for output 7 -bit integers left justified

%-10s indicates the output of the word aligns alignment

2. Some special provisions of the character

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character Action

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\ nthe line break

\f Clear screen and change page

\ r Enter

\ t Tab character

\xhh represents an ASCII code with an x-input representation, where HH is 1 to 2 decimal digits

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Char c, s[20], *p;

int a=1234, *i;

float f=3.141592653589;

Double x=0.12345678987654321;

P= "How does You Do";

strcpy (S, "Hello, comrade");

*i=12;

c= ' \x41 ';

printf ("a=%d\n", a); /* result output decimal integer a=1234*/

printf ("a=%6d\n", a); /* Results Output 6 -bit decimal number a= 1234*/

printf ("a=%06d\n", a); /* Results Output 6 -bit decimal number a=001234*/

printf ("a=%2d\n", a); /*a more than 2 bits, output by actual value a=1234*/

printf ("*i=%4d\n", *i); /* output 4 -bit decimal integer *i= 12*/

printf ("*i=%-4d\n", *i); /* output left-justified 4 -bit decimal integer *i=12*/

printf ("i=%p\n", I); /* output address i=06e4*/

printf ("f=%f\n", f); /* output floating-point number f=3.141593*/

printf ("f=6.4f\n", f); /* output 6 -bit floating-point number with 4 digits after the decimal point f=3.1416*/

printf ("x=%lf\n", X); /* output long floating-point number x=0.123457*/

printf ("x=%18.16lf\n", x);/* outputs The long floating-point number of which the decimal point is x=0.1234567898765432*/

printf ("c=%c\n", c); /* output character c=a*/

printf ("c=%x\n", c); /* ASCII code value for output character c=41*/

printf ("s[]=%s\n", s); /* output array string S[]=hello, comrade*/

printf ("s[]=%6.9s\n", s);/* outputs a string of up to 9 characters s[]=hello,co*/

printf ("s=%p\n", s); /* output array string first character address s=ffbe*/

printf ("*p=%s\n", p); /* output pointer string p=how do do*/

printf ("p=%p\n", p); / * The value of the output pointer p=0194*/

the address values in the above results may be different on different computers.

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C + + format string description