C Programming Language Lecture Notes

Introduction to C Language

• Invented by Dennis Ritchie at AT&T Bell Laboratories in the early 1970s.
• Influenced by earlier B language and its ancestors.
• Middle Level Language: Used for system-level programming (like OS) and application development (games).

Characteristics of C Language

• Structured Programming: Programs organized into functions and modules.
• Object-Oriented Programming: C++ is the extension of C for OOP.

Getting Started with C

• Compiler Required: Install GCC or Clang.
• File Extension: C files end with .c.
• Main Function: Every C program requires a mandatory main() function.
• Header Files: Use #include to include other C files, ending with .h (e.g., #include <stdio.h>).

Basic Concepts

Keywords and Data Types

• Keywords: 32 keywords in C language.
• Primary Data Types:
  • char: Characters.
  • int: Integer values.
  • float: Decimal values (up to 6 decimal places).
  • double: Decimal values (up to 15 decimal places).
  • void: No value (often used in functions).

Variables

• Declare variable: specify data type and variable name.
• Rules for Declaring Variables: Refer to specific rules given in the course.
• Assigning Values: Can be done upon declaration or later.
• Statements End with Semicolon.

Input and Output

• Printing Output: Use printf() with format specifiers.
  • Example: printf("%d", variable_name);
• Reading Input: Use scanf().
  • Example: scanf("%d", &variable_name); (use & for address).

Operators

• Arithmetic Operators: For basic calculations.
• Relational Operators: For comparing values.
• Logical Operators: Combine expressions (e.g., &&, ||).

Control Structures

Conditional Statements

• if Statement: Syntax: if (condition) { // statements }
• else Statement: Follows if to execute if the condition is false.
• Nested if-else: Allows multiple conditions.
• Switch Statement: Selects block of code based on variable value.
  • Syntax: switch(variable) { case value: // statements; break; }

Loops

• Types of Loops:
  • while Loop: Checks condition before executing.
  • do-while Loop: Executes at least once before checking the condition.
  • for Loop: More control over iterations.
    • Syntax: for (initialization; condition; increment/decrement) { // code }

Functions

• Definition: Block of code performing a specific task.
• Declaration: Return type, function name, parameters.
• Calling a Function: Use the function name with arguments.

Arrays and Pointers

Arrays

• Collection of data items of the same type.
• Syntax: data_type array_name[size];
• Access elements using index (starting from 0).

Pointers

• Variables that store memory addresses.
• Declare using * before the variable name.
• Use & to get the address and * to dereference.

Strings and Structures

Strings

• Strings are arrays of characters.
• Use char string_name[size];
• Format specifier for strings: %s.

Structures

• Definition: Collection of different data items.
• Declaration: struct structure_name { // items };
• Access elements using dot notation.

Unions

• Allows storing different data types in the same memory location.
• Only one member can hold a value at a time.
• Declaration similar to structures but use union.

Comments

• Single Line Comments: Use //.
• Multi-Line Comments: Start with /* and end with */.

Compiling C Programs

• Use GCC: gcc filename.c -o output_filename

Conclusion

• Understanding these basics is crucial for effective programming in C.