C Programming Data Types and Declaration

Data Types

• C has several built-in data types:
  • Integers: int, short, long, unsigned int, etc.
  • Floating-point numbers: float, double, long double
  • Characters: char
  • Boolean: No built-in type, but often represented using int (0 for false, 1 for true)
  • Void: void (no value)

Declaration

• A variable must be declared before it can be used
• Declaration syntax: data_type variable_name;
  • Example: int x;
• Multiple variables can be declared in a single statement, separated by commas
  • Example: int x, y, z;

Assignment

• Assignment operator: =
• Syntax: variable_name = value;
  • Example: x = 10;
• Assignment can be done at declaration time or later in the code

Initialization

• Initialization is a combination of declaration and assignment
• Syntax: data_type variable_name = value;
  • Example: int x = 10;
• Initialization is optional, but recommended to avoid undefined values

Scope

• Scope refers to the region of the code where a variable is accessible
• Variables have one of the following scopes:
  • Local: Variables declared inside a function or block, accessible only within that scope
  • Global: Variables declared outside all functions, accessible from any function
  • Static local: Variables declared inside a function, but retain their value between function calls
  • External: Variables declared in one file, accessible from other files

Data Types

• C has several built-in data types, including integers, floating-point numbers, characters, and void.
• Integers can be int, short, long, or unsigned int.
• Floating-point numbers can be float, double, or long double.
• The character data type is char.
• Boolean is not a built-in type, but often represented using int (0 for false, 1 for true).
• The void data type has no value.

Declaration

• A variable must be declared before it can be used.
• The declaration syntax is data_type variable_name;.
• Multiple variables can be declared in a single statement, separated by commas.

Assignment

• The assignment operator is =.
• The assignment syntax is variable_name = value;.
• Assignment can be done at declaration time or later in the code.

Initialization

• Initialization is a combination of declaration and assignment.
• The initialization syntax is data_type variable_name = value;.
• Initialization is optional, but recommended to avoid undefined values.

Scope

• Scope refers to the region of the code where a variable is accessible.
• Variables have one of four scopes: local, global, static local, or external.
• Local variables are declared inside a function or block and are only accessible within that scope.
• Global variables are declared outside all functions and are accessible from any function.
• Static local variables are declared inside a function, but retain their value between function calls.
• External variables are declared in one file and are accessible from other files.