C Programming Tokens and Characters

White Space Characters

• Tab: '\t'
• Newline: '\n'

Character Set

• Represented by ASCII codes

C Tokens

• The smallest building blocks of a C program
• Include keywords, identifiers, constants, operators, and punctuation marks

Types of C Tokens

• Keywords: Reserved words with fixed meanings
  • Cannot be redefined by the user
  • Examples: int, float, char, void
• Identifiers: User-defined names for variables, arrays, functions, and other program elements
  • Must follow specific rules:
    • Start with an alphabet or underscore
    • Digits can be used after the first character
    • Cannot contain spaces or special symbols
    • Cannot be keywords
    • Case sensitive
• Constants: Fixed values that cannot be changed during program execution
  • Examples: 10, 3.14159, 'A', "Hello"
• Operators: Symbols that perform specific operations on data
  • Examples: +, -, *, /, %, =, >, <
• Punctuation Marks: Symbols used to separate or organize C code
  • Examples: {, }, ;, ,

Datatypes

• Define the type of data that a variable can hold
• Determine the amount of memory allocated for a variable
• Used in variable declarations

Classification of Datatypes

• Primary Datatypes: Also called built-in or fundamental data types
  • Examples: char, int, float, double
• Derived Datatypes: Created using primary data types
  • Examples: Arrays, structures, pointers, unions
• User-defined Datatypes: Defined by programmers using keywords like enum, struct, and typedef

Primary Data Types

• char: Stores single characters
  • Encoded using the ASCII character set
  • Occupies 1 byte of memory
• int: Stores whole numbers (integers)
  • Can be signed (positive, negative, and zero) or unsigned (only positive and zero)
  • Occupies 2 or 4 bytes of memory depending on the system architecture
• float: Stores single-precision floating-point (decimal) numbers
  • Provides 4 bytes of memory for storage
• double: Stores double-precision floating-point numbers
  • Provides 8 bytes of memory for storage
  • Often used for higher precision calculations

Qualifiers/Modifiers

• Used to alter the size and sign of primary data types
• Size: short, long
• Sign: signed, unsigned

Variables

• Named memory locations that can store values
• Can be modified during program execution
• Must be declared before use
• Can be initialized during declaration
• Memory Address: The location of the variable in memory.
• Value: The data stored in the variable.
• Name: The identifier used to access the variable.

Types of Variables

• Local: Declared inside a function
  • Scope is limited within the function
• Global: Declared outside of all functions
  • Scope is accessible throughout the program

Constants

• Fixed values that cannot be changed during program execution
• Useful for representing unchanging data, such as mathematical constants or configuration settings

Types of Constants

• Integer Constants: Whole numbers
  • Decimal: Base-10 numbers (e.g., 123)
  • Octal: Base-8 numbers (e.g., 0177)
  • Hexadecimal: Base-16 numbers (e.g., 0x4b)
• Real Constants: Floating-point numbers (decimals)
  • Fractional Form: e.g., 3.14159, -0.005
  • Exponential Form: e.g., 1.23e4
• Character Constants: Single characters enclosed in single quotes
  • e.g., 'A', '5', '$'
• String Constants: Sequences of characters enclosed in double quotes
  • e.g., "Hello", "World", "123"

Operators

• Symbols that perform mathematical, logical, or other operations on data

Symbolic Constants

• Defined using the #define directive
• Used to give meaningful names to constants
• Can be used throughout the program

Program Structure

• Link Section: Includes header files (e.g., stdio.h, math.h)
• Definition Section: Defines constants using #define
• Global Declaration Section: Declares global variables and functions
• Global Function Section: Contains global functions
• Main Function Section: The entry point for program execution
  • Must have int main() {}
  • Contains declaration and execution statements
• User-Defined Function Section: Contains user-defined functions

Sections of a C program

• #include <stdio.h>: Header file for standard input/output functions
• #define PI 3.14: Symbolic constant declaration
• int main(): The main function
• // Welcome to C: Single-line comment
• void myfunction(): A user-defined function
• int a = 10, b = 20;: Global variable declaration

Execution

• The program begins execution at the main() function.

Explore the foundational elements of C programming in this quiz, focusing on various types of C tokens including keywords, identifiers, constants, and operators. Test your understanding of character sets and whitespace characters integral to writing effective C code.