tutorial variables

Variables and Data Types

In C, data is stored as variables.

Data Types

Each variable is associated with a data type.

By default, the following types are available: (this list is not complete)

Name	Size (bytes)	Format Specifier	Description
char	1	%c	8-bit number or single ASCII character
int	2	%d or %i	2-byte signed integer
unsigned int	2	%u	2-byte unsigned integer
long	4	%d or %i	Larger signed integer
unsigned long	4	%u	Larger unsigned integer
float	4	%f or %F	4-byte floating point number (decimal number)
double	8	%e, %E, %g, or %G	Larger floating point number

NOTE: long long (64-bit integer) isn't fully supported by our compiler. Using a long long is just asking for trouble, especially if you attempt to divide it.

More explicit types can be accessed by adding #include <stdint.h> to the top of the program. This gives you access to the following types:

Name Format	Size	Format Specifier	Example	Description
uintX_t	X	%d or %i	uint16_t	X-bit unsigned integer
intX_t	X	%u	int32_t	X-bit signed integer

Declaring variables

Declare a variable by putting the desired data type in front of the desired name:

#include <stdint.h>
int main() {
    uint32_t x = 100000
    x = x + 1
    printf("%d\n", x);     // Prints x; shows 100001
}

Assignment

In C, assignment is denoted with =, with the value to be assigned on the left.

x = 5;      // 5 -> x
x = x + 1;  // x + 1 -> x

WARNING: assignment is always =. Comparison is done with ==. For example,

if(x = 5) {
    printf("%d\n", x);
}

will always print 5, since x = 5 assigns x as 5.