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C Programming
Unit - I

Introductory Concepts & C Fundamentals

1. Introductory Concepts

Types of Programming Languages

  • Low-Level Languages: These languages are closer to machine code and are hardware-specific. Examples include:

    • Machine Language: Consists of binary instructions (0s and 1s) that the computer understands directly.
    • Assembly Language: Uses mnemonics (like ADD, MOV) and needs an assembler to convert to machine code.

  • High-Level Languages: These are closer to human language, making them easier to learn and use. Examples include C, Python, and Java.

Introduction to C

  • C Language: Created by Dennis Ritchie in 1972, C is a powerful general-purpose language used for system programming, developing operating systems, and other performance-critical applications. It provides low-level access to memory and is structured.

Some Simple C Programs

  • Hello World Example:
#include <stdio.h>
int main() {
    printf("Hello, World!\n");
    return 0;
}
  • This program prints "Hello, World!" on the screen. The #include directive imports the standard input/output library, main() is the entry point, and printf() outputs the message.

Desirable Program Characteristics

  • Readability: Code should be easy to understand.
  • Modularity: Code is organized into reusable functions.
  • Efficiency: Programs should minimize resource usage (CPU, memory).
  • Maintainability: Code should be easy to update or modify.

2. C Fundamentals

C Character Set

  • Letters: A to Z, a to z.
  • Digits: 0 to 9.
  • Special Characters: +, -, *, /, =, {, }, etc.
  • Whitespace: Spaces, tabs, and newlines are used to separate tokens.

Identifiers and Keywords

  • Identifiers: Names for variables, functions, etc. Must begin with a letter or an underscore.
    • Example: int total;, float marks;.
  • Keywords: Reserved words in C (e.g., int, return, if) that cannot be used as variable names.

Data Types

  • Basic Data Types:

    • int: For integers (whole numbers), e.g., int x = 5;.
    • float: For floating-point numbers (decimals), e.g., float y = 3.14;.
    • char: For single characters, e.g., char ch = 'A';.
    • double: For large floating-point numbers.

  • Derived Data Types: Arrays, pointers, structures.

Constants, Variables, and Arrays

  • Constants: Fixed values that do not change, defined using #define or the const keyword.
    • Example: #define PI 3.14159.
  • Variables: Named storage locations in memory.
    • Example: int age = 21;.
  • Arrays: A collection of variables of the same type stored sequentially in memory.
    • Example: int numbers[5] = {1, 2, 3, 4, 5};.

Declarations, Expressions, and Statements

  • Declarations: Allocate memory for variables, e.g., int a;.
  • Expressions: Combine variables and operators to produce a result, e.g., a + b.
  • Statements: Instructions that perform an action, e.g., a = 5;.

Symbolic Constants

  • A symbolic name is given to a constant value using #define.
    • Example: #define MAX 100.
Unit - II