Introduction to C Programming

Introduction to C Language

• C is a middle-level language combining high-level language features with assembly language control and flexibility.
• It's derived from ALGOL 60 (1960) and evolved through predecessors like ALGOL, BCPL, and B.
• Standardization began in 1983 by ANSI, approved in 1989, then adopted by ISO in 1990 as C89.
• Minor changes led to C95 in 1995, followed by significant updates in 1999, forming C99.

Objectives

• Understand the structure of a C program.
• Write a basic C program.
• Introduce the include preprocessor command.
• Create good identifiers for program quantities.
• Explain and use basic data types in C.
• Create and use variables and constants in C programs.

Agenda

• Background of the C Language
• Structure of a C program
• C comments
• Identifiers in C
• Data types in C
• Variables in C
• Constants in C

Features of C

• Structured programming language with compartmentalization of code and data.
• Supports multiple looping constructs like while, do-while, and for.
• Allows statements to be placed anywhere on a line without strict field concept.
• Discourages or prohibits the use of the goto statement.

Structure of a C Program

• Preprocessor Directives: Include standard libraries (e.g., stdio.h) for input/output. (This comes first)
• Global Declarations: Declares data visible throughout the program. (Optional)
• main Function: The starting point of every C program, contains local declarations and statements within curly brackets {}
• Local Declarations: Data declared within the function. (Optional)
• Statements: Instructions executed within the program.
• Other Functions: Optional modules for specific tasks.

Dissecting a Minimal C Program

• #include <stdio.h>: A preprocessor command to include the standard input/output library.
• int main(void): The main function which returns an integer value (0 usually).
• printf("Welcome to Computer Programming");: Instruction that prints a message to the screen.
• return 0;: Instruction instructing the program to end.

Creating and Compiling a Minimal C Program

• Create the program in a text editor.
• Save the file with the .c extension (e.g., welcome.c).
• Compile the code using a compiler (e.g., cc welcome.c).
• Compile and Link to create an executable file.
• Save the program with a .c file extension.

Executing a Minimal C Program

• Locate the compiled executable file (a.out).
• Run the program by typing ./a.out. This displays the output.

Summary of Writing and Executing a C Program

• The steps to create and run a C program (editing, compiling, linking and running).
• Diagram showing the process from editing the code to executing.

C Comments

• Comments help explain sections of code.
• They're disregarded by the compiler.
• Include two formats: line comments (//) and block comments (/* */).

Line Comments

• Use '//' to denote a line comment.
• Comments end at the end of the line and can be at the beginning, middle, or end of a line.

Block Comments

• Use '/* */' to enclose multiline comments
• The compiler skips everything within these opening and closing symbols
• These can span multiple lines.

Caution with Comments

• Comments should not be nested (i.e., one inside the other). This would result in an error.

Minimal C Program Revisited with Comments

• Example of a minimal C program with explanation of comments, preprocessor directives, and functions.

The C Character Set

• Includes alphabets (A-Z, a-z), digits (0-9), and special symbols (~!@#$%^&*()_+=-`[]{}|;:'",./<>?).

Escape Sequence Characters

• Two characters (e.g., '\n') to perform a special task.
• Example characters and representations.

Identifiers in C

• Names given to variables to represent data.
• Can include letters from A-Z and a-z and underscore.
• Must start with a letter or underscore.
• Rules for creating identifiers.

Some Keywords/Reserved Words in C

• Keywords with pre-defined meanings that cannot be used as identifiers.

Examples of Valid and Invalid Identifiers

• Examples of valid and invalid identifier names along with reasons.

Types in C

• Categorization of data types (void, integral, floating-point, and derived) with detailed explanations.

Void Type

• A data type with no values or operations.
• Useful in functions when no parameters or returns are needed.

Integral Types

• Types that contain only whole numbers, excluding fractions.
• Includes boolean, character, and integers.

Boolean Type

• Represents logical values (True or False).

Character Type

• Stores one character, typically 8 bits.

Integer Types

• Stores whole numbers without decimal places. Includes short int, int, long int, and long long int.

Floating-Point Types

• Stores real numbers with decimal points, like float, double, and long double.

Imaginary Type

• A component of the complex data type.

Complex Type

• Another component of the C complex data type.

Variables in C

• Named memory locations that hold data.
• Must be declared for the compiler to manage memory.

Variable Declaration

• Statement to reserve space for variables of a particular type.

Variable Definition

• Allocate memory for the variable and assign its initial value.

Variable Initialization

• Providing an initial value when a variable is declared.

Constants in C

• Fixed data values that cannot change during program execution.

Boolean Constants

• Represent true/false conditions (0 or 1).

Character Constants

• A single character enclosed within single quotes.

Escape Characters

• Special characters (e.g., \n for newline).

Integer Constants

• Whole number values, including the use of L and U indicators for integer values.

Real Constants

• Real numbers, including specifying form using f and F for float type real values and L for long double.

Imaginary Constants

• Imaginary parts of complex numbers.

Complex Constants

• Complex numbers.

String Constants

• A sequence of characters enclosed in double quotes.

Literal Constants

• Named constants in C, similar to literal data input, not using the #define method

Defined Constants

• Using #define to create named constants

Memory Constants

• Creating constants using the const keyword.

Exercises

• Practice questions on various aspects of C programming

Solutions to Exercises

• Answers to the practice questions.