C Data Types

Derived Data Types:

Derived data types in C are data types that are created by combining or modifying the fundamental or basic data types in some way. They are derived from the primary data types and include pointers, arrays, structures, and unions. Here's an overview of these derived data types:

Pointers: Pointers are variables that store memory addresses. They allow you to work with the memory locations of other data types. Pointer types are derived from the basic data types they point to. For example, an int* is a pointer to an integer, and a char* is a pointer to a character.

Arrays: Arrays are collections of elements of the same data type stored in contiguous memory locations. The array itself is considered a derived data type. For example, an 'int[]' is an array of integers.

User-Defined Data Types:

In C, you can define custom data types using various mechanisms. Here are some common ways to define custom data types:

typedef: The 'typedef' keyword allows you to create a new name for an existing data type. It's often used to improve code readability or to create custom data type names. For example:

typedef int Age;
Age personAge = 30;

In this example, 'Age' is defined as a new name for the 'int' data type.

struct: You can use the struct keyword to create a composite data type that groups together variables of different data types. For example:

struct Point {
    int x;
    int y;
};

struct Point p1;
p1.x = 10;
p1.y = 20;

Here, a custom data type 'struct Point' is defined to represent a point with 'x' and 'y' coordinates.

Union: Similar to 'struct', you can use 'union' to define a composite data type, but in a union, all members share the same memory location. This can be useful in situations where you want to represent data that can be one of several types. For example:

union Variant {
    int intValue;
    float floatValue;
    char stringValue[20];
};

union Variant data;
data.intValue = 42;

Here, 'union Variant' can hold an integer, a float, or a string, but only one at a time.

enum: The enum keyword allows you to create an enumerated data type with a set of named values. For example:

enum Days { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday };
enum Days today = Wednesday;

In this case, 'enum Days' defines a custom data type with named constants for days of the week.

Format Specifiers

C format specifiers are placeholders used in format strings to control how data is formatted and displayed when using functions like printf and scanf. They are used to specify the type and formatting of data that is to be input or output. Here are three commonly used C format specifiers with their meanings:

Data Types	Formats	Meanings
int	%d	Respects a decimal integer value.
	%u	Respects an unsigned integer value.
	%o	Respect an unsigned octal value.
	%x	Respect an unsigned hexadecimal value.
float	%f	Represents a floating point value.
	%e	Floating value in decimal or exponential form.
char	%c	Represents a single character value.
	%s	Represents a strings of value of characters.