Type Size

In C, the "size" (in memory) of a type is not guaranteed to be the same on all systems. That's because the size of a type is dependent on the system's architecture. For example, on a 32-bit system, the size of an int is usually 4 bytes, while on a 64-bit system, the size of an int is usually 8 bytes - of course, you never know until you run sizeof with the compiler you plan on using.

However, some types are always guaranteed to be the same. Here’s a list of the basic C data types along with their typical sizes in bytes. Note that sizes can vary based on the platform (e.g., 32-bit vs. 64-bit systems):

Basic C Types and Sizes:

• char

  • Size: 1 byte
  • Represents: Single character.
  • Notes: Always 1 byte, but can be signed or unsigned.

• float

  • Size: 4 bytes
  • Represents: Single-precision floating-point number.

• double

  • Size: 8 bytes
  • Represents: Double-precision floating-point number.
  • The actual sizes of these types can be determined using the sizeof operator in C for a specific platform, which we'll learn about next.

#include <stdio.h>

int main() {
  printf("char:   %zu bytes\n", sizeof(char));
  printf("float:  %zu bytes\n", sizeof(float));
  printf("double: %zu bytes\n", sizeof(double));

  char c = 'A';
  float f = 3.14f;
  double d = 2.71828;

  printf("Variable char:   %zu bytes\n", sizeof(c));
  printf("Variable float:  %zu bytes\n", sizeof(f));
  printf("Variable double: %zu bytes\n", sizeof(d));

  return 0;
}