What are the basic scalar data types in C?

Three families: integer types (char/short/int/long/long long, signed or unsigned), floating-point (float/double/long double), and pointers.

Integer types:

// 1 byte, often used for characters
char c;
// At least 2 bytes
short int s;
// At least 2 bytes (usually 4)
int i;
// At least 4 bytes
long int l;
// At least 8 bytes (C99)
long long int ll;

Signed vs unsigned:

// Can be negative (default)
signed int si;
// 0 or positive only
unsigned int ui;
// 0-255
unsigned char uc;

Floating-point:

// ~7 decimal digits precision
float f;
// ~15 decimal digits precision
double d;
// Extended precision
long double ld;

Pointers:

// Pointer to int
int *p;
// Pointer to pointer to pointer to char
char ***c;

Read pointer declarations right-to-left:

• int *p → "p is a pointer to int"
• char **argv → "argv is a pointer to pointer to char"

Tip: Use https://cdecl.org/ to decode complex C declarations!

Go deeper:

• C data types — Wikipedia — the arithmetic types and their size guarantees.