Program Structure in C

Program Structure in C

• Documentation Section: Contains metadata such as program name, date, description, and title. Formatted as either // ProgramName or enclosed in /* Overview of the code */.

• Preprocessor Section: Includes all header files required by the program. Utilizes the #include directive to link libraries during compilation. Key libraries include standard input/output files for stdin, stdout, and stderr.

• Definition Section: Involves constant declarations using the define keyword to create fixed values for use in the program.

• Global Declaration: Contains all global declarations that can be accessed throughout the entire program, thereby providing shared visibility.

• Main Function:

  • The entry point of a C program, executed first by the computer.
  • Must include at least one main function defined as either int main() or void main().
  • Categorized into:
    • Local Declarations: Variables defined within a function, e.g., int i = 2;.
    • Statements: Control structures like if, else, while, for that dictate flow.
    • Expressions: Combinations of values and operators, e.g., a - b;.

• Return Function: Typically the last segment of the main function, used to return a value when the return type is not void.

Tokens in C

• Definition: The smallest individual element in a C program, crucial for forming syntactically correct code.

• Classification of Tokens: Includes:

  • Keywords: Pre-defined reserved words with specific functionality, e.g., int, float, if.
  • Identifiers: User-defined names for variables, functions, arrays, etc. Must begin with a letter or underscore, be case-sensitive, and cannot exceed 31 characters.
  • Strings: A sequence of characters enclosed in double quotes.
  • Operators: Symbols that perform operations on data (e.g., +, -, *, /).
  • Constants: Fixed values that do not change during program execution, e.g., numeric literals.
  • Special Characters: Symbols that have specific roles, like semicolons and braces.

Data Types and Constants

• Common Data Types:

  • int: Whole numbers, 2 or 4 bytes.
  • float: Fractional numbers, requiring 4 bytes.
  • double: More precise fractional numbers, 8 bytes.
  • char: Single characters or ASCII values, 1 byte.

• Void Data Type: Represents no value, used for functions that do not return a value.

Variable Declaration and Initialization

• Declaration: Informs the compiler about variable types and storage requirements. The syntax includes the data type followed by variable names (e.g., int a, b;).

• Initialization: Assigns a value at the time of declaration. Syntax includes the variable name followed by an equal sign and a value (e.g., int x = 10;).

User Defined Type Declaration

• Type Definition: Allows the creation of new identifiers for existing data types, enabling custom data types which can be used for variable declaration later.

This quiz covers the essential components of a C program, including the documentation, preprocessor, definition, and main function sections. You'll explore key concepts such as global declarations and local variables. Test your understanding of how these elements work together to form a coherent C program.