[C] Data Type 자료형

Data type means the type of variables. Variables refer to an object to transfer or store a value as the code proceeds. In particular, since C is a programming language that can access memory addresses, it is important to set an appropriate type according to the type of data for efficient coding. Data types mainly used in C language are as follows.

Data Type	Volume(B)	Min Value	Max Value
char	1	0	127
signed char	1	-128	127
unsigned char	1	0	255
signed short	2	-32768	32767
unsigned short	2	0	65535
(signed) int	4	-2147483648	2147483647
unsigned int	4	0	4294967295
signed long	4	-2147483648	2147483647
unsigned long	4	0	4294967295
signed long long	8	-9223372036854775808	9223372036854775808
unsigned long long	8	0	18499744073709551615

Data Type	Volume(B)	Min Value	Max Value
float	4	3.4e-37	3.4e+38
double	8	1.7e-307	3.4e+308

The real data cannot be used in octal or hexadecimal format, and only decimal representation is allowed. Also, the real data is signed without the concept of unsigned. The basic type of integer is signed int, the basic type of character is char, and the basic type of real is double. I/O format specifier without a predetermined data type is recognized as a default data type. The corresponding format specifiers are as follows.

Format Specifier	Data Type
%d	int, short
%ld	long
%lld	long long int
%u	unsigned int
%f	float
%lf	long double, double
%c	char
%s	string
%p	pointer

The last %p is a format specifier to the address of the variable. Also, the %s format specifier means a string.
In the code below, int i=427 means that the type of i is defined as int, and an integer 427 is assigned to this variable. Since the integer data type was used, the i variable allocates and uses the 4B memory area.

    #include <stdio.h>

    int main(void){
        int i=427;
        double a=427.427427427427;

        printf("%d\n", i);
        printf("%f\n", a);
        printf("%lf\n", a);


        return 0;
    }   

427
427.427427
427.427427