Chapter 2 · Lesson 1

Data Types in C

C has a small set of basic data types:

Integer Types:

char: 1 byte (also used for characters)
short: At least 2 bytes
int: At least 2 bytes (usually 4)
long: At least 4 bytes
long long: At least 8 bytes

Floating Point:

float: Single precision (4 bytes)
double: Double precision (8 bytes)
long double: Extended precision

Modifiers:

signed: Can hold negative values (default)
unsigned: Only positive values

sizeof Operator: Returns the size in bytes of a type or variable.

Type Qualifiers:

const: Value cannot be changed
volatile: May change unexpectedly (hardware)

Code Examples

C Data Typesc

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

int main() {
    // Integer types
    char c = 'A';
    short s = 32767;
    int i = 2147483647;
    long l = 2147483647L;
    long long ll = 9223372036854775807LL;
    
    printf("char: %c (ASCII: %d)\n", c, c);
    printf("int: %d\n", i);
    
    // Unsigned types
    unsigned int ui = 4294967295U;
    printf("unsigned int: %u\n", ui);
    
    // Floating point
    float f = 3.14159f;
    double d = 3.141592653589793;
    
    printf("float: %.5f\n", f);
    printf("double: %.15f\n", d);
    
    // sizeof operator
    printf("\nSizes in bytes:\n");
    printf("char: %zu\n", sizeof(char));
    printf("int: %zu\n", sizeof(int));
    printf("long: %zu\n", sizeof(long));
    printf("float: %zu\n", sizeof(float));
    printf("double: %zu\n", sizeof(double));
    
    // Constants
    const double PI = 3.14159265359;
    printf("\nPI: %.11f\n", PI);
    
    // Type limits
    printf("\nInt range: %d to %d\n", INT_MIN, INT_MAX);
    
    return 0;
}

C data type sizes can vary by platform. Always use sizeof() when you need exact sizes. limits.h contains type range constants.

Quick Quiz

1. What's the minimum guaranteed size of an int in C?

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Code Examples

C Data Typesc

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

int main() {
    // Integer types
    char c = 'A';
    short s = 32767;
    int i = 2147483647;
    long l = 2147483647L;
    long long ll = 9223372036854775807LL;
    
    printf("char: %c (ASCII: %d)\n", c, c);
    printf("int: %d\n", i);
    
    // Unsigned types
    unsigned int ui = 4294967295U;
    printf("unsigned int: %u\n", ui);
    
    // Floating point
    float f = 3.14159f;
    double d = 3.141592653589793;
    
    printf("float: %.5f\n", f);
    printf("double: %.15f\n", d);
    
    // sizeof operator
    printf("\nSizes in bytes:\n");
    printf("char: %zu\n", sizeof(char));
    printf("int: %zu\n", sizeof(int));
    printf("long: %zu\n", sizeof(long));
    printf("float: %zu\n", sizeof(float));
    printf("double: %zu\n", sizeof(double));
    
    // Constants
    const double PI = 3.14159265359;
    printf("\nPI: %.11f\n", PI);
    
    // Type limits
    printf("\nInt range: %d to %d\n", INT_MIN, INT_MAX);
    
    return 0;
}

C data type sizes can vary by platform. Always use sizeof() when you need exact sizes. limits.h contains type range constants.