Programming Ch.5

Chapter 5: C Functions

5.1 Introduction

• Real-world programs are often large; to maintain them, they should be constructed from smaller, manageable pieces known as functions.

• The divide-and-conquer technique is emphasized to manage program complexity effectively.

5.2 Modularizing Programs in C

• Functions are crucial for modularizing C programs.

• C standard library includes numerous pre-packaged functions for math calculations, string manipulations, and others.

• Good programming practice encourages familiarity with standard library functions instead of re-inventing them.

• Standard functions (e.g., printf, scanf, pow) hide implementation details, promoting software engineering principles.

• Each function executes tasks designated by the caller and returns results.

5.3 Math Library Functions

• Common mathematical calculations are achievable using math library functions (e.g., sqrt).

• Arguments can be constants, variables, or expressions, and results typically return the data type double.

• Essential math functions include:

  • sqrt(x): square root.

  • pow(x, y): x raised to the power y.

  • fabs(x): absolute value.

  • sin, cos, tan: trigonometric functions.

5.4 Functions

• Functions create modular programs with local variables and parameters.

• The motivation for using functions includes manageability, reusability, and avoiding code duplication.

• Each function should perform one clear task, and names should reflect this to promote clarity.

5.5 Function Definitions

• Functions consist of a prototype and definition.

• A function prototype must match the definition; improper prototypes lead to compilation errors.

• The syntax of a function definition includes the return type, function name, and parameter list.

• Example definitions:

  • int square(int y): Returns the square of y.

  • int maximum(int x, int y, int z): Returns the maximum of three integers.

5.6 Function Prototypes: A Deeper Look

• Prototypes facilitate type checking and error prevention in function calls.

• Good practice includes prototypes for better code maintenance and fewer errors.

5.7 Function Call Stack and Stack Frames

• The call stack is essential for maintaining function calls, return addresses, and local variable information.

• Stack frames are created upon the calling of a function and are removed when functions return.

• Stack overflow errors can occur if there are too many nested function calls.

5.8 Headers

• Each standard library has associated headers that contain function prototypes necessary for use.

• Programmers can create custom headers to organize their functions effectively.

5.9 Passing Arguments By Value and By Reference

• Arguments can be passed by value (copy) or by reference (direct access).

• Pass-by-value avoids accidental changes to variables in the calling function, while pass-by-reference allows for modifications.

5.10 Random Number Generation

• Randomness can be introduced in applications using rand() from <stdlib.h>.

• To achieve specific ranges, scaling and shifting are used with rand().

• For secure applications, use secure random number generators.

5.11 Example: A Game of Chance; Introducing enum

• The enum type provides a means to create meaningful constant names, simplifying code readability.

• Used in games (e.g., craps) to indicate game status.

5.12 Storage Classes

• Identifiers in C have different storage classes (auto, register, extern, static) affecting their duration and linkage.

• Automatic duration applies to local variables; static variables retain values between function calls.

5.13 Scope Rules

• Scope defines where identifiers are accessible; includes function scope, file scope, block scope, and function-prototype scope.

• Hiding variables in inner blocks can lead to errors if not managed properly.

5.14 Recursion

• Recursive functions call themselves directly or indirectly, solving problems by handling base cases and simplifying the problem.

• Example: Factorial calculation using recursion demonstrates self-referential calling.

• Caution with recursion as it can lead to exponential complexity if not managed properly.

5.15 Example Using Recursion: Fibonacci Series

• Fibonacci sequence is defined recursively, illustrating natural occurrences and relationships.

• Recursive Fibonacci functions showcase rapid growth in call count and potential performance issues.

5.16 Recursion vs. Iteration

• Both techniques involve repetition; recursion does so through function calls while iteration uses loops.

• Recursive solutions can be easier to understand even with added overhead costs.

5.17 Secure C Programming

• The standard library lacks secure random-number generation; alternative platform-specific implementations are encouraged.

These notes provide an in-depth overview of functions in C programming, covering modularity, math libraries, recursion, and function management practices.