C Programming Chapter 1: Variables & Constants

C Programming Notes

• Computer programming is a medium for communicating with computers, similar to using languages like Hindi or English to communicate with each other.
• Programming instructs the computer.
• C is an old and refined programming language.
• C was developed by Dennis Ritchie at Bell Labs, USA in 1972.
• C is used for numerous system components, including major parts of Windows and Linux operating systems.
• C is used for device drivers, such as those for tablets and printers.
• C is used to program embedded systems, like microwaves and cameras.
• These systems need fast programs to react swiftly to user input.

Chapter 1: Variables, Constants & Keywords

• Variables act as containers to store values (e.g., rice, dal, sugar).
• Variables in C store values like integers, decimals, or characters.
• Variables in C must start with an alphabet or an underscore, followed by further alphabets, underscore, or digits.
• No special symbol (e.g., @, #, $, %) or commas or blanks are allowed.
• Variable names are case-sensitive (e.g., 'myVariable' is different from 'myvariable').
• Constants are entities whose values never change.
• Variables can change their values.

Types of Constants

• Integer constants: Whole numbers (e.g., -1, 6, 7, 9)
• Real constants: Numbers with decimal points (e.g., -322.1, 2.5, 7.0)
• Character constants: Single characters enclosed in single quotes (e.g., 'a', '$', '@')

Keywords

• Keywords are reserved words with pre-defined meanings known to the compiler.
• There are 32 keywords in C.
• Examples of C keywords:

  auto, double, int, struct
  break, else, long, switch
  case, enum, register, typedef
  char, extern, return, union
  const, float, short, unsigned
  continue, for, signed, void
  default, goto, sizeof, volatile
  do, if, static, while
  

First C Program

• A simple C program example:

#include <stdio.h>
int main() {
printf ("Hello, I am learning C with Harry");
return 0;
}

Basic Structure of a C Program

• Every C program's execution begins with the main() function.
• Each statement in C ends with a semicolon (;).
• Instructions are case-sensitive.
• Instructions are executed in the order they are written.

Comments

• Comments clarify the program's logic.
• Single-line comments start with //.
• Multi-line comments are enclosed in /* */.
• Comments are ignored during compilation.

Compilation & Execution

• The compiler converts a C program into machine language for the computer to understand.
• A C program is typically written in plain text, with instructions arranged sequentially.
• The compiler checks the instructions and turns them into an executable file.
• C programs use library functions, like printf, which handle specific tasks, such as displaying values on the screen.

Types of Variables

• Integer variables store whole numbers (e.g., int a = 3).
• Real variables store decimal numbers (e.g., float a = 7.7, double a = 7.7).
• Character variables store single characters (e.g., char a = 'A').

Receiving Input from the User

• Use the scanf function to receive input from the user and assign it to a variable.
• The & operator is important in scanf; it indicates the memory address where the input should be stored.

Chapter 2 - Practice Set

• Includes questions to solve practical C programming problems.

Chapter 2: Instructions and Operators

• Types of instructions.
• Arithmetic instructions.
• Control instructions.
• Examples of different variations of instructions and relevant errors.

Arithmetic Instruction and Operators

• List of arithmetic operators in C (+, -, *, /, %)
• Rules governing operators.
• Examples showing the execution of different variations of operators.

Type Conversion

• How integers and floats get converted during arithmetic operations.

Operator Precedence in C

• Rules for determining the order of evaluation in a C expression.

Control Instructions

• Sequence control instruction.
• Decision control instruction.
• Loop control instruction.
• Case control instruction.

Conditional Instructions

• if-else statements for decision-making based on conditions.
• switch statements for multiple-choice situations.

Logical Operators

• Logical operators in C for implementing complex conditions (&&, ||, !).
• Rules, precedence and how they translate to truth and false contexts.

Types of Loops

• while loop for repeating a block of code as long as a condition is true.
• do-while loop for executing a block once and repeating it while a condition is true
• for loop for repeating a block of code a predetermined number of times.
• Loop control commands: break, continue.

Chapter 4 - Practice Set

• Questions for practice on executing different types of loops and the relevant control commands.

Project 1: Number Guessing Game

• Project to create a game where the user guesses a random number.

Chapter 5 : Functions and Recursion

• Functions are reusable blocks of code.
• Function prototypes, calls, and definitions.
• How to call functions and obtain return values.
• Recursion: functions that call themselves.
• Examples include factorial calculation.

Chapter 5 - Practice Set

• Practical programming problems utilizing functions and recursion.

Chapter 6: Pointers

• Pointers store memory addresses.
• Using pointers to access address and values.
• Pointer declaration (int *ptr;, char *ptr).
• The & and * operators.
• How to pass values to a function using pointers by reference.

Chapter 6 - Practice Set

• Practical problems on pointers.

Chapter 7: Arrays

• Arrays: store multiple sequential data elements (same data type.)
• Array declaration and initialization.
• Accessing array elements.
• Arrays in memory: Contiguous storage
• How to initialize an array.

Chapter 7 - Practice Set

• Exercises to practice the concepts of arrays and pointers used accessing array elements.

Chapter 8: Strings

• Strings as arrays of characters.
• Declaration by character array and string literal.
• Useful string functions (strlen, strcpy, strcmp, strcat).
• How to input/output strings (e.g., user input using scanf).

Chapter 8 - Practice Set

• Problems on string manipulation, using the library functions.

Chapter 9: Structures

• Structures: grouping data items (different data types) into a single unit.
• Structure declaration, initialization.
• Structures in memory (contiguous allocation for members).
• How to pass structures to functions.
• Use of typedef keyword in creating aliases for structures (optional topic).

Chapter 9 - Practice Set

• Exercises to enhance understanding of structures, passing data through functions and memory management.

Chapter 10: File I/O

• Reading and writing data from files.
• File pointers, opening files, reading from files, writing to files, closing files.
• Special file handling functions (fopen, fscanf, fprintf, fgetc...).
• File opening modes ('r', 'w', 'a').

Chapter 10 - Practice Set

• Problems of combining files, and reading/writing data into them.

Project 2: Snake, Water, Gun

• Game-dev project involving loops and choices.

Chapter 11: Dynamic Memory Allocation

• Dynamically allocating memory during program execution (using malloc, calloc).
• Deallocating memory when not needed (using free).
• realloc function for changing allocated memory size.

Chapter 11 - Practice Set

• Practical problems involving dynamic memory allocation, reallocation of different data type and size of these elements.