Unit II: Introduction to Computing

Table of Contents

1. Art of Programming through Algorithms
2. Flowcharts: Symbols and Rules
3. Overview of C: History and Importance
4. Basic Structure and Execution of C

1. Art of Programming through Algorithms

An Algorithm is a step-by-step procedure or a set of rules to be followed in calculations or other problem-solving operations. Before writing actual code, programmers use algorithms to define the logic of the program.

Qualities of a Good Algorithm:

Finiteness: It must terminate after a finite number of steps.
Definiteness: Each step must be clearly defined and unambiguous.
Input: It should have zero or more well-defined inputs.
Output: It must produce at least one output.
Effectiveness: Steps must be basic enough to be carried out exactly.

2. Flowcharts: Symbols and Rules

A Flowchart is a pictorial or graphical representation of an algorithm. It uses various symbols to represent different types of operations.

Flowchart Symbols:

Symbol Name	Shape	Purpose
Terminal	Oval / Ellipse	Indicates the START or END of a program.
Input/Output	Parallelogram	Used for reading data (Input) or printing results (Output).
Processing	Rectangle	Used for calculations or data manipulation.
Decision	Diamond	Represents a condition (Yes/No or True/False branch).
Flow Lines	Arrows	Indicates the direction of program flow.

Rules for Designing Flowcharts:

Flow should usually be from top to bottom or left to right.
Only one flow line should come out of a process symbol.
Only one flow line should enter a decision symbol, but two or three may leave it.
Avoid intersection of flow lines for better clarity.

3. Overview of C: History and Importance

C is a powerful general-purpose programming language developed by Dennis Ritchie at Bell Laboratories in the early 1970s.

History: It was originally developed to write the UNIX operating system.
Importance: C is known for its efficiency and portability. It provides low-level access to memory while remaining easy to read for humans. Most modern languages like C++, Java, and Python have roots in C.

4. Basic Structure and Execution of C

A C program follows a specific template to ensure the compiler can process it correctly.

Basic Structure of a C Program:

Documentation Section: Comments about the program.
Link Section: Header file inclusions (e.g., #include <stdio.h>).
Definition Section: Defining symbolic constants.
Global Declaration Section: Declaring variables used throughout the program.
Main Function: The entry point where execution begins (main() { ... }).
Subprogram Section: User-defined functions.

Executing a C Program:

The execution involves four main steps:

Creating the Program: Writing code in an editor and saving it as .c.
Compiling: The compiler checks for syntax errors and converts code to an object file.
Linking: Linking the object file with library functions to create an executable (.exe).
Running: Executing the program to see the output.

Exam Tips

Flowchart Accuracy: Always use a diamond for "if" conditions and a parallelogram for "print" or "input" statements.
Algorithm vs. Flowchart: Algorithms are text-based; Flowcharts are image-based. Both describe the same logic.
C History: Mentioning Dennis Ritchie and UNIX in history questions usually earns extra points.

Frequently Asked Questions

Q1: Why is C called a "middle-level" language?
Because it combines features of high-level languages (human readability) with the power and efficiency of low-level languages (memory manipulation).

Q2: Can a flowchart have multiple start points?
No, a flowchart must have exactly one START terminal to represent the beginning of execution.