C Programming: Character Constants and Escape Sequences

Character Constants

• A character constant is a constant enclosed in single quotation marks, e.g., 'a', 'l', 'm', 'F'.
• Escape sequences are used to represent characters that cannot be typed or have special meanings in C programming.

Escape Sequences

• Examples of escape sequences include \n for newline, \t for tab, and ? for question mark.
• The backslash () causes the compiler to "escape" from the normal interpretation of characters.

String Constants

• String constants are enclosed in double quotation marks, e.g., "Hello, World!".
• String constants are used to represent a sequence of characters.

Enumeration Constants

• The keyword enum is used to define enumeration types.
• Enumeration constants have values, e.g., yellow, green, black, and white have values 0, 1, 2, and 3, respectively.

Data Types

• In C programming, variables or memory locations must be declared before use.
• Data types refer to the type and size of data associated with variables and functions.

Integer Data Types

• Integers are whole numbers with no decimal values, e.g., 0, -5, 10.
• The keyword int is used to declare integer variables.

Keywords and Identifiers

• Character set includes alphabets, letters, and special characters that are valid in C language.
• C accepts both lowercase and uppercase alphabets as variables and functions.

Keywords

• Keywords are predefined, reserved words used in programming that have special meanings to the compiler.
• Examples of keywords include int, char, and void.

Identifiers

• Identifiers refer to names given to entities such as variables, functions, and structures.
• Identifiers must be unique and cannot be used as keywords.

Rules for Writing an Identifier

• A valid identifier can have letters, digits, and underscores.
• The first letter of an identifier should be a letter or an underscore.
• Identifier names must be different from keywords.

Variables

• A variable is a container to hold data.
• Each variable should be given a unique name (identifier).
• Variables can be assigned values, and the values can be changed.

Rules for Naming a Variable

• A variable name can have letters, digits, and underscores.
• The first letter of a variable should be a letter or an underscore.
• Variable names must be different from keywords.