2. Data Types & Qualifiers

1. Data Types in C

Data types specify the type and size of data that can be stored in a variable. C categorizes data types into three main types:

1. Primary (Fundamental) Data Types: Built-in types that form the basis for all other types.
   • int (Integer values)
   • char (Single character values)
   • float (Single-precision floating-point values)
   • double (Double-precision floating-point values)
   • void (Empty/No value)
2. Secondary (User-Defined) Data Types: Data types created by the user to group data.
   • struct (Structures)
   • union (Unions)
   • enum (Enumerated types)
   • typedef
3. Tertiary (Derived) Data Types: Data types that are derived from primary data types.
   • Arrays
   • Pointers
   • Functions

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2. Data Type Qualifiers (Modifiers)

Qualifiers are keywords used to modify the properties (size or sign) of primary data types to fit specific needs.

1. Size Qualifiers

Used to alter the memory size allocated to a data type.

• short: Decreases the memory size (usually minimum 2 bytes). Used when small numbers are expected to save memory.
• long: Increases the memory size (usually minimum 4 or 8 bytes) to store very large numbers.

2. Sign Qualifiers

Used to specify whether a variable can hold negative values or only positive values.

• signed: Can store both negative and positive values (default for int and char).
• unsigned: Can store only zero and positive values. By removing negative numbers, it doubles the maximum positive range.

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3. Sizes and Ranges (Standard 32/64-bit Systems)

Note: The exact size may vary depending on the compiler and architecture, but these are the standard typical sizes.

Data Type / Qualifier	Size in Bytes	Size in Bits	Range	Format Specifier
char (or signed char)	1 byte	8 bits	-128 to +127	%c
unsigned char	1 byte	8 bits	0 to 255	%c
short int (signed)	2 bytes	16 bits	-32,768 to +32,767	%hd
unsigned short int	2 bytes	16 bits	0 to 65,535	%hu
int (signed)	4 bytes	32 bits	-2,147,483,648 to +2,147,483,647	%d or %i
unsigned int	4 bytes	32 bits	0 to 4,294,967,295	%u
long int (signed)	4 or 8 bytes	32 or 64	Varies based on architecture	%ld
unsigned long int	4 or 8 bytes	32 or 64	Varies based on architecture	%lu
long long int	8 bytes	64 bits	-(2^63) to (2^63)-1	%lld
float	4 bytes	32 bits	6 decimal places of precision	%f
double	8 bytes	64 bits	15 decimal places of precision	%lf
long double	10 or 16 bytes	80 or 128	19 decimal places of precision	%Lf

Example Usage of Qualifiers

#include <stdio.h>

int main() {
    short int a = 1000;
    unsigned int b = 4000000000; // Positive only
    long long int c = 9000000000000000000LL;
    
    printf("Size of short int: %zu bytes\n", sizeof(a));
    printf("Size of unsigned int: %zu bytes\n", sizeof(b));
    printf("Size of long long int: %zu bytes\n", sizeof(c));
    
    return 0;
}