Data types - C

Data type	bytes
bool	1
int	4
long	8
float	4
double	8
char	1
string	?

• int

  • whole numbers
  • 4 bytes of memory (32 bits)
  • The range of values they can store is necessarily limited to 31 bits worth of information
  • $-2^{31}\text{ to }{2}^{31}-1$
  • • 2 billion to 2 billion

• unsigned int

  • unsigned is a qualifier, that can be applied to certain types (including int), which effectively doubles the positive range of variables of that type at the cost of disallowing any negative values
  • $0\text{ to }{2}^{32}-1$
  • 0 to 4 billion

• char

  • single characters
  • 1 byte of memory (8 bits)
  • We’ve developed a mapping of characters to numeric values using ASCII
  • $-2^7\text{ to }{2}^7-1$
  • -128 to 127

• float

  • used for variables that will store floating-point values - real numbers
  • 4 bytes of memory (32 bits)
  • It has a precision problem
    • ex) look at $\pi$, it goes on forever - there is a limitation coz we only have 32 bits

• double

  • variables that will store floating-point values, also known as real numbers
  • 8 bytes of memory (64 bits) - double the precision
    • additional 32 bits from float

• void

  • is a type but not a data type
  • functions can have a void return type or a void parameter

• In C, boolean and string are NOT built in!

  • use the #include <cs50.h>

Creating variables

// declaration
int number;
int height;
 
int height, number; // works, but bad practice
 
// assignment
number = 10;
 
// initialization
char letter = 'H';