STRUCTURED PROGRAMMING

3. Program structure

Data types in C are broadly classified into three categories:

These are the basic built-in types provided by the C language.

Data Type	Keyword	Description	Typical Size (bytes)	Format Specifier
Integer	`int`	Stores whole numbers (positive or negative).	2 or 4	`%d`
Character	`char`	Stores a single character (letter/symbol).	1	`%c`
Float	`float`	Stores numbers with decimal points (single precision).	4	`%f`
Double	`double`	Stores large decimal numbers (double precision).	8	`%lf`
Void	`void`	Represents the absence of value (used in functions).	0	-

These are derived from the fundamental data types to handle complex data.

Arrays: A collection of elements of the same data type (e.g., a list of 10 integers).
Pointers: Variables that store the memory address of another variable.
Functions: A block of code that returns a value of a specific data type.

These allow the programmer to define their own data structures.

Structure (struct): A collection of variables of different data types grouped together under a single name (e.g., a "Student" structure containing name, age, and marks).
Union (union): Similar to structures, but all members share the same memory location.
Enumeration (enum): Consists of named integer constants (e.g., enum Week {Mon, Tue, Wed}).

Modifiers are used with basic data types (specifically int and char) to alter the size or range of data they can hold.

signed: The variable can hold both positive and negative numbers (default for int).
unsigned: The variable can hold only positive numbers (doubles the positive range).
short: Reduces the storage size (usually 2 bytes).
long: Increases the storage size (usually 4 or 8 bytes).

Example of Modifier Usage:

C

short int age = 20;          // Uses less memory
unsigned long int distance;  // Uses more memory, positive values only

In structured programming, you must declare a variable's data type before using it.

Syntax: data_type variable_name;

Examples:

C

int score = 95;
float pi = 3.142;
char grade = 'A';
double salary = 50000.50;