Function Definition and Parameters Quiz

Function Definition

• The general form of a function definition includes a return type, function name, parameters enclosed in parentheses, and a function body enclosed in curly braces.
• The function body contains declarations for local variables and statements that execute the function's logic.

Parameters

• Parameters are variables declared within the function's parentheses.
• Each parameter is specified with its data type.
• Parameters are separated by commas.
• The keyword "void" is used when a function has no parameters.

Local Variables

• Local variables are declared within the function body.
• Their scope is restricted to the enclosing function, meaning they are only visible and accessible within that function.
• They have automatic storage duration, allocated when the function is called and deallocated when the function returns.

Parameter Properties

• Parameters have the same properties as local variables, including automatic storage duration and block scope.
• They are automatically initialized with values from the corresponding arguments when the function is called.

Passing Arguments

• Arguments are values passed to a function during a function call.
• Arguments allow information transfer to the function.

External Variables

• External variables are declared outside any function.
• Their scope is global, accessible from any part of the program.
• They are also known as global variables.

Function Definitions

• General form: return-type function-name ( parameters ) { declarations statements }
• Parameters:
  • Preceded by type specification
  • Separated by commas
  • If no parameters, use void between parentheses
• Local variables:
  • Declared within the function body
  • Visible from declaration to end of enclosing function body
• Block scope:
  • Local variables are only visible within the function block
  • Functions can use the same variable names for different purposes
• Automatic storage duration:
  • Memory is allocated when the function is called and deallocated when it returns

Local Variables and Parameters

• Local variables and parameters have the same storage duration and scope
• Parameters are automatically initialized when a function is called with corresponding argument values

Passing Information to Functions

• Arguments: One way to transmit information to a function
• External variables (global variables): Declared outside any function body, accessible by all functions
• Pointers:
  • Used to store memory addresses
  • Declared with an asterisk (*) before the variable name
  • int *p; declares a pointer variable p that points to an integer

Pointer Operations

• Address operator (&):
  • Used to find the address of a variable
  • For example: &i gives the address of the variable i
• Indirection operator (*):
  • Used to access the value that a pointer points to
  • For example: *p gives the value stored at the address pointed to by p
• Pointer initialization:
  • Assign it the address of a variable
  • p = &i; assigns the address of i to pointer p, making p point to i
• Pointer assignment:
  • q = p; copies the address stored in p to q
• Dereference assignment:
  • *q = *p; copies the value pointed to by p to the memory location pointed to by q

Decomposing Numbers

• decompose() function: Takes a double x, a pointer to an integer int_part and a pointer to a double frac_part
• Functionality:
  • *int_part = (int) x; assigns the integer part of x to the memory location pointed to by int_part
  • *frac_part = x - *int_part; assigns the fractional part of x to the memory location pointed to by frac_part

Pointer Arithmetic

• Purpose:
  • To navigate through arrays using pointers
• Supported operations:
  • Adding an integer to a pointer
  • Subtracting an integer from a pointer
  • Subtracting one pointer from another
• Restrictions:
  • You cannot add two pointers

String Manipulation

• Copying strings: strcpy(char *s1, const char *s2);
  • Copies the string pointed to by s2 into the array pointed to by s1
  • Returns s1 (a pointer to the destination string)

Command-line Arguments

• Purpose: Provide information to the program when it is executed
• main function parameters:
  • argc: Represents the number of command-line arguments
  • argv: An array of pointers to strings, where each element points to a command-line argument
  • argv[0] points to the name of the program
  • argv[1] through argv[argc-1] point to the remaining command-line arguments