C - Type System in C

Definition

The type system in C defines the rules for declaring variables, functions, and expressions, specifying:

• What kind of data can be stored

• How much memory is allocated

• What operations are permitted on that data

Data Types in C (Type System Classification)

1. Basic (Primitive) Data Types

Used to store simple values.

Example:

int a;
float b;
char c;

2. Derived Data Types

Derived from basic data types.

• Arrays

• Pointers

• Structures

• Unions

Example:

int arr[10];
int *p;

3. User-Defined Data Types

Created by programmers.

• struct

• union

• enum

• typedef

Example:

typedef int marks;

4. Void Type

• Represents no value

• Used for functions that do not return anything

Example:

void display();

Importance of Type System

• Ensures type safety

• Helps in error detection

• Determines memory allocation

• Improves code readability and reliability

Type Conversion in C

Definition

Type conversion is the process of converting a value from one data type to another.

C supports two types of type conversion:

1. Implicit (Automatic)

2. Explicit (Type Casting)

1. Implicit Type Conversion

• Done automatically by the compiler

• Occurs when different data types are used in an expression

• Smaller data type is converted into larger data type

Example:

int a = 10;
float b = a;

Here, int is automatically converted to float.

Usual Type Promotion Order

char → int → float → double

Example:

int a = 5;
float b = 2.5;
float c = a + b;   // a converted to float

2. Explicit Type Conversion (Type Casting)

• Done manually by the programmer

• Used when forced conversion is required

Syntax:

(type) expression

Example:

int a = 10, b = 3;
float result = (float)a / b;

Without casting, result would be 3.

Type Conversion in Expressions

Example:

int a = 5;
double b = 2.0;
double c = a * b;

Here, a is converted to double.

Type Conversion in Assignment

Example:

float f = 10.75;
int x = f;

Fractional part is truncated → x = 10

Problems Due to Improper Type Conversion

• Loss of precision

• Unexpected results

• Overflow or underflow

• Logical errors

Difference Between Implicit and Explicit Conversion