C data types

February 28, 2022

Here are the basic data types for C programs.

Think of these as buckets of memory. You’ve got small buckets and big buckets. When you’re writing a C program you can pick the buckets that are best suited for your data.

Type	Explanation	Minimum size (bits)⁽¹⁾
`char`	This is the smallest addressable data type. It can represent numbers [-127, +127] or [0, 255]. I say "or" because whether `char` is `signed` or `unsigned` is platform dependant.	8
`unsigned char`	This is the same size as a `char`, but it's gauranteed to be signed, meaning it can represent numbers [-127, +127].	8
`signed char`	This is the same size as a `char`, but it's gauranteed to be unsigned, meaning it can represent numbers [0, 255].	8
`short` `short int` `signed short` `signed short int`	Can represent numbers [-32,767, +32,767]	16
`unsigned short` `unsigned short int`	Can represent numbers [0, 64,535]	16
`int` `signed int`	Can represent numbers [-32,767, +32,767]	16
`long` `long int` `signed long` `signed long int`	Can represent numbers [-2,147,483,647, +2,147,483,647]	32
`unsigned long` `unsigned long int`	Can represent numbers [0, 4,294,967,295]	32
`long long` `long long int` `signed long long` `signed long long int`	Can represent numbers [−9,223,372,036,854,775,807, +9,223,372,036,854,775,807]	64
`unsigned long long` `unsigned long long int`	Can represent numbers [0, +18,446,744,073,709,551,615]	64
`float`	Typically, this represents a 32 bit decimal number. That said, it's platform dependant.
`double`	Typically, this represents a 64 bit decimal number. That said, it's platform dependant.

1. The C specification only states the minimum size of a data type. The implementation details are left up to the compiler writers based on their target platform.