Introduction to Computer Languages, C, and Flowcharts

Computer Languages

• Machine Level Language:

  • Lowest-level language composed of binary digits ($0$ and $1$) directly executed by the CPU.

  • Advantages: Very fast execution with no translation required, direct control over hardware, memory efficient.

  • Disadvantages: Difficult to read and write, machine-dependent, error-prone.

• Assembly Level Language:

  • Uses mnemonic abbreviations (e.g., MOV, ADD, JMP) to represent machine instructions.

  • Requires an Assembler to translate code into machine code.

  • Advantages: Easier to read and write than machine code, mnemonics are easy to remember.

  • Disadvantages: Machine-dependent, complex compared to high-level languages.

• High-Level Languages:

  • Close to human language; includes control structures, I/O facilities, and built-in functions (e.g., FORTRAN, COBOL, PASCAL, C, C++, Java, Python).

  • Advantages: Machine-independent (portable), easier to learn, faster development time.

  • Disadvantages: Slower execution, requires a compiler or interpreter, provides less direct hardware control.

Introduction to C Language

• Origin: Developed by Dennis Ritchie at Bell Laboratories in 1972 to construct the UNIX operating system.

• Key Features: High-speed execution, highly versatile, foundational syntax shared with Java, Python, C++, and C#.

• C vs. C++: C++ extends C by adding support for classes and objects, which C lacks.

C Header Files

• Purpose: Files carrying a .h extension that contain forward declarations of functions, data types, and macros without definitions, adhering to the One Definition Rule.

• Categories:

  • User-Defined: Created by developers and located in the working directory.

  • Standard Library: Located in system directories (e.g., stdio.h).

• Syntax: Included using the #include <header-file-name.h> preprocessor directive.

Program Code Types

• Source Code: Human-readable high-level or assembly code created by developers; easily alterable.

• Object Code: Low-level machine code in binary format generated by a compiler or translator; executable by the CPU and non-modifiable.

• Executable Code: Compiled and linked machine-level instructions loaded into main memory (RAM) for execution.

Algorithms

• Definition: A finite, well-defined sequence of steps designed to perform a computation or solve a specific problem.

• Properties: Precisely defined inputs/outputs, clear and unambiguous steps, language-independent.

• Addition Algorithm Example:

  1. Start

  2. Declare variables num1, num2, and sum

  3. Read num1 and num2

  4. Calculate $\text{sum} \rightarrow \text{num1} + \text{num2}$

  5. Display sum

  6. Stop

Flowcharts

• Definition: Visual representations of an algorithm using standard visual shapes and directional arrows.

• Standard Symbols:

  • Terminal/Terminator (Oval): Represents Start, Stop, or Halt in execution flow.

  • Input/Output (Parallelogram): Represents input reading or output display operations.

  • Action/Process (Rectangle): Represents arithmetic operations and general data processing.

  • Decision (Diamond): Represents conditional branching (e.g., True/False, Yes/No).

  • On-Page Connector (Circle): Connects distinct flowchart sections on the same page.

  • Flow Lines (Arrows): Direct the sequence of execution flow.