IO

The "IO" standard input and output, and we can easy input/output our data in format by function followedf

Format

For convenience reason, we want to quick read/write value from stdout/``stdin` with variable. We have idea of format.

For example printf("%d\n", var); print int type var

• "%d": define the variable type, if the type of var is different will raise error, but char can present int by ASCII, vice versa
• "\n": mean new line
• var: the respective variable of format

That's is, the format is the string, we can print variable in the given format or scan value write into variable in this way.

For example, we can have some format like "the %d person is %c\n" follow two variable to print the result we want, or read from stdin we want. Since we define "%" to read/write variable, we need know about what value followed to correctly present variable.

Notice for format that read, for example "the %d person is %c\n" we should input the 1 person is A to correctly read 1 and A into variable.

Input	Meaning	Type
c	a single character	char
s	a string	char *
d	integer	int
f	float number	float
e/E	in scientist notation	double
l/ld/li	long integer	long
lf	long float	double
p	pointer	void *

Furthermore, we can add extra stuff to print more specific value.

For int, we can use 0n to extend the length of number by add 0 at head. For example printf("%04d", 1); will have a output 0001. That's 0n means extend to n length when n larger than the length of the variable.

Similarly, for float/double, we can use .n to specific the decimal place, for example printf("%.2f", 1.3459834); will have a output 1.35. But notice, round will apply for this.