Introduction to C Programming

Introduction to C

• C was developed in 1972 by Dennis Ritchie at Bell Laboratories.
• Initially developed for writing system software.
• Now a popular language used to write various software programs.

Characteristics of C

• High-level programming language.
• Relatively easy to learn with only 32 keywords.
• Extensive use of function calls.
• Stable and quick language.
• Core language.
• Portable (platform-independent).
• Extensible.

Uses of C

• Primarily used for system programming.
• Portability, efficiency, and ability to access specific hardware addresses make it suitable for implementing operating systems and embedded system applications.
• Low runtime demand on system resources.

Structure of a C Program

• Documentation Block: Optional block for programmer comments and program description. Uses single-line comments (//) or multi-line comments (/* ... */).
• Preprocessor Directives Block: Contains special instructions to prepare the program for compilation. The include directive is commonly used to access header files.
• Global Declarations Block: Declares global variables that are available throughout the entire program. Global variables are declared outside the main function.
• Main Block (main()): The entry point of every C program. Execution begins here.
• Function Block: Contains user-defined functions (subprograms) to perform specific tasks.
  • Functions can be built-in/library functions or user-defined functions. User-defined functions are declared outside of main(). Each defined function has a name given to it.
  • Local declarations and statements are found within the curly braces {}.

Your First C Program

• Example showing a simple C program that displays a welcome message.
• Includes necessary header files (e.g., stdio.h, conio.h).

Files Used in a C Program

• Source File: Contains the source code of the program. Has a .c extension.
• Header File: Contains predefined standard library functions and subroutines. Has a .h extension. Useful when dealing with large projects to store subroutines and have standardized code for various programs.
• Object File: Contains compiled code (binary) from source code. Generated by the compiler. Has a .o or .obj extension.
• Executable File: Contains linked code (binary) that can be directly run (executed). Created by a linker from one or more object files. Has a .exe extension (Windows).

Compiling and Executing C Programs

• Two-step compilation process:
  • Preprocessor reads source files as text and generates an intermediate text file as an output.
  • Linker combines the object file with library routines to create an executable file.

Tokens

• Tokens are the smallest building blocks of a C program (words and punctuation).
  • Keywords: Reserved words with fixed meanings (e.g., int, float, if).
  • Identifiers: User-defined names for program elements (e.g., variables, functions). Rules for naming identifiers.
  • Constants: Fixed values that don't change (e.g., numbers, characters).
  • Special characters: Punctuation marks with special meanings in C.
  • Operators: Symbols representing operations to be performed (e.g., +, -, *).

Keywords

• Set of 32 reserved words, typically lowercase.

Identifiers

• User-defined names for program elements (variables, arrays, functions, structures).
• Can include lowercase letters, uppercase letters, digits or underscores.
• Must start with an alphabet or underscore.
• Cannot include special characters or punctuation marks (except underscore)
• Case-sensitive (e.g., FIRST is different from first).
• Should not be longer than 31 characters and cannot be a reserved keyword.

Constants

• Fixed values that do not change during program execution.
• Types include integers, floating-point numbers, characters, and strings.
• Declared using const or via the #define preprocessor directive.

Special Characters

• Symbols in C programs that have specific meanings.
  • Examples include parentheses, brackets, curly braces, commas, etc.

Data Types

• Data types are used to specify the type of data a variable can hold. This allows the compiler to allocate appropriate memory space and determine valid operations using that variable.
  • Primitive/basic types like integers, characters and floating point numbers.
• Modifiers (e.g. signed,unsigned,double,short,long). Modifiers can change the size and meaning of a basic type.

Variables in C

• Represent memory locations that can store data.
• Variables can be numeric (integers or floating-point) or character type.
• Declared using a data type followed by variable name (e.g. int x;).
• Initialized with a value during declaration (e.g. int x = 5;).
• Variables are given meaningful names to represent values in programs.

Constants in C

• Identified constant values written in the program, which can be declared either by using the const keyword or via the preprocessor directive #define. These values do not change during program execution.

Escape Sequence Characters

• Special sequences of characters in C programs that don't represent their literal meaning when embedded within strings.
  • Useful for representing special characters (e.g., newline, tab).

This quiz covers the basics of the C programming language, including its history, characteristics, and uses. Participants will explore the structure of a C program, including key components and best practices. Perfect for beginners looking to understand the fundamentals of C.