Unit 2: Art of Programming and C Overview

1. Art of Programming through Algorithms and Flowcharts
2. Overview of C Programming

1. Art of Programming through Algorithms and Flowcharts

Before writing code, a programmer must plan the logic. This "art of programming" is done using algorithms and flowcharts.

An Algorithm is a finite, step-by-step, unambiguous set of instructions to solve a specific problem.

Example: Algorithm to add two numbers

Start
Declare three variables: num1, num2, sum.
Read values for num1 and num2.
Calculate sum = num1 + num2.
Display sum.
Stop

Qualities of a Good Algorithm

A good algorithm must have the following properties:

Input: It must take zero or more well-defined inputs.
Output: It must produce one or more well-defined outputs.
Finiteness: It must terminate after a finite number of steps.
Definiteness/Unambiguous: Each step must be clear and precisely defined.
Effectiveness: Each step must be simple enough to be carried out (e.g., "add two numbers" is effective; "find the best move" is not).

Flowchart Symbols

A Flowchart is a graphical or pictorial representation of an algorithm. It uses standard symbols to show the sequence of operations.

Symbol	Name	Function
Oval / Terminal	Start / Stop	Indicates the beginning or end of the flowchart.
Parallelogram	Input / Output	Used for reading data (Input) or displaying results (Output).
Rectangle	Process	Represents an operation or calculation (e.g., `sum = a + b`).
Diamond	Decision	Used for asking a question (e.g., `is a > b?`). Has one entry and two exits (Yes/No).
Arrows	Flow Lines	Show the direction and sequence of operations.

Rules for designing Flowcharts

A flowchart should have only one Start and one Stop symbol.
The flow of logic should generally be from top to bottom or left to right.
A decision (diamond) symbol must have two exit points (Yes, No).
All symbols must be connected by flow lines (arrows).

2. Overview of C Programming

History and Importance of C

History: C was developed in the early 1970s by Dennis Ritchie at Bell Labs. It was created to write the UNIX operating system.
Importance:
- It is a "middle-level" language: it has high-level features (portability, easy-to-read) and low-level features (pointer manipulation, direct memory access).
- It is extremely fast and efficient.
- It is the foundation for many other languages (C++, C#, Java, Python) and modern operating systems (Windows, Linux, macOS).

Basic Structure of C program

Every C program follows a standard structure.

#include   // Preprocessor Directive

// Global declarations (if any)

int main() {        // The main function where execution begins
    
    // Variable declarations
    int num;
    
    // Program statements
    printf("Hello, World!");
    
    return 0;   // Return statement
}

#include : A preprocessor directive that tells the compiler to include the "Standard Input/Output" header file (which contains printf, scanf, etc.).
int main(): The main function. Every C program must have one. Execution *always* starts here.
{ ... }: The curly braces define the "body" or block of the function.
return 0;: Tells the operating system that the program executed successfully.

Executing a C program

The process from writing code to getting an output involves several steps:

Create (Write) Source Code: Save your program as a .c file (e.g., hello.c).
Compile: Use a compiler (like gcc) to translate the source code into machine-readable object code (hello.o). The compiler also checks for syntax errors.
Link: A Linker combines your object code with any necessary library code (like the code for printf) to create a final executable file (e.g., hello.exe or a.out).
Execute (Run): You run the executable file, and the computer performs the instructions.