前面加0b表示二进制
加0x表示十六进制
数字前加0表示八进制
‘ ‘ //ASCII值是63
‘\077’ //是8进制表示’ ‘，0可以省略，因为C,C++规定不允许使用斜杠加10进制数来表示字符
‘\0x3F’ //是16进制表示’ ‘
关键字 位长(字节) 范围 格式化字符串
char 1 -128..127（或0..255，与体系结构相关） %c
unsigned char 1 0..255
signed char 1 -128..127
int 2(16位系统)或4 -32768..32767 或-2147483648..2147483647 %i, %d
unsigned int 2或4 0..65535 或0..4294967295 %u
signed int 2 或4 -32768..32767 或-2147483648..2147483647 %i, %d
short int 2 -32768..32767 %hi
unsigned short 2 0..65535 %hu
signed short 2 -32768..32767 long int 4 或8[3] -2147483648..2147483647或-9223372036854775808..9223372036854775807 %li, %ld
unsigned long 4 或8 0..4294967295 或0..18446744073709551615 %lu
signed long 4 或8 -2147483648..2147483647或-9223372036854775808..9223372036854775807
long long 8 -9223372036854775808..9223372036854775807 %lli
unsigned long long 8 0..18446744073709551615 %llu
float 4 3.4x10 38..3.4x10+38 (7 sf) %f, %e, %g
double 8 1.7x10 308..1.7x10+308 (15 sf) %f, %e, %g
long double 8 或以上 编译器相关 %Lf, %Le, %Lg