C - Datatypes

C provides fundamental types like char, int, float, and double, plus modifiers like short, long, and unsigned.

Learning Objectives

• Choose appropriate types for different values and ranges.
• Understand signed vs unsigned and size modifiers.
• Use sizeof to determine type sizes.

Prerequisites

• C - Variables

Basic Types

#include <stdio.h>

int main(void) {
  char c = 'A';                    // typically 1 byte
  int i = 42;                      // typically 4 bytes
  float f = 3.14f;                 // typically 4 bytes
  double d = 3.141592653589793;    // typically 8 bytes
  
  printf("char: %c (size: %zu)\n", c, sizeof(c));
  printf("int: %d (size: %zu)\n", i, sizeof(i));
  printf("float: %.2f (size: %zu)\n", f, sizeof(f));
  printf("double: %.15f (size: %zu)\n", d, sizeof(d));
}

Modifiers

#include <stdio.h>
#include <limits.h>

int main(void) {
  short s = 32000;
  long l = 2000000000L;
  unsigned int u = 4000000000U;
  long long ll = 9000000000000LL;
  
  printf("short: %d (range: %d to %d)\n", s, SHRT_MIN, SHRT_MAX);
  printf("unsigned: %u (range: 0 to %u)\n", u, UINT_MAX);
  printf("long long: %lld\n", ll);
}

Common Pitfalls

• Integer overflow wraps around for unsigned types but is undefined for signed.
• Comparing signed and unsigned values can give unexpected results.
• Using wrong format specifiers for printf (e.g., %d for long).

Checks for Understanding

1. What's the difference between float and double?
2. What happens when an unsigned char exceeds 255?
3. How do you print a long long?

Practice

1. Choose appropriate types for: age, bank balance, pixel color (0-255), population count.
2. Use sizeof to print the size of each basic type on your system.