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Essential Fundamentals

How Computer Works

Computer works on binary number system. Because it's based on electronic, and in electronic, signals are low or high which means 0 or 1.

Block Diagram

Number Systems

  • Binary = {0, 1}
  • Octal = {0, 1, 2, 3, 4, 5, 6, 7}
  • Decimal = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
  • HexaDecimal = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F}
Decimal Binary Octal HexaDecimal
0 0 0 0
1 1 1 1
2 10 2 2
3 11 3 3
4 100 4 4
5 101 5 5
6 110 6 6
7 111 7 7
8 1000 10 8
9 1001 11 9
10 1010 12 A
11 1011 13 B
12 1100 14 C
13 1101 15 D
14 1110 16 E
15 1111 17 F
16 10000 18 10
  • Computer is a programmable computation device.
  • A Program contains Data and set of Instructions.
  • Intermediate language between human language and machine language is called programming language.

Low-level, High-Level & Hybrid Languages

  • Low level language :

    • Machine Language (Binary)
    • Assembly

  • High level languages :

    • C, C++, Java, Python, C#, etc
    • Compiler bases languages : C++
    • Interpreter based languages : Javascript
    • Hybrid languages

  • Hybrid Languages :

    • Java, dot net languages - C#
    • They have both compiler and interpreter.
    • It's 2 step stages.
    • Compiler just check for error, not generate machine code, it's just byte code. JVM (interpreter) will generate machine code and also execute.
    • Interpreter for byte code not for source code.

Compiler vs Interpreter

  • Compiler :

    • Compiler converts source code to machine code (only if no error).
    • Generate executable file.
    • For running program we don’t require compiler.
    • Compiler programs are faster, run independently.

  • Interpreter :

    • Chrome works is an interpreter for java script.
    • Chrome translate one line and execute it also.
    • Line by line translation as well execution.
    • Will not create exe file.
    • Interpreter languages are easier compared to compiler based languages.
    • Example : Preparing a Chinese dish from reading a Chinese recipe book.

Operating System : A Master Program

Operating System

Program Development

Programming Paradigm

  • There are many type of Programming Paradigm, like Imperative, procedural, functional, declarative, object oriented, etc.

Programming Paradigm

Flow Chart

  • A flowchart is a type of diagram that represents a workflow or process.
  • A flowchart can also be defined as a diagrammatic representation of an algorithm.
  • It's a step-by-step approach to solving a task.
  • Example :

Flow Chart

Steps for Program Development and Execution

  • Coding/Editing
  • Compiling
  • Linking Library (Header Files)
  • Loading (Bringing program from hard disk to main memory)
  • Execution

Main Memory divided into 4 sections

  • Stack :

    • Used to store local variables and function call information
    • Each function call creates a new stack frame, and local variables are allocated within that frame.
    • Memory allocated on the stack is automatically reclaimed when a function exits.

  • Heap :

    • Used for dynamic memory allocation
    • Memory allocated on the heap persists until explicitly deallocated by the programmer.

  • Code Section (Text Section) :

    • Machine code copied into code section.
    • Holds the executable code of a program.

  • Data Section :

    • Contains global and static variables used by the program
    • Initialized Data Section :
      • Holds initialized global and static variables.
      • The values of these variables are set at compile time.
    • Uninitialized Data Section (BSS - Block Started by Symbol) :
      • Holds uninitialized global and static variables.
      • The values of these variables are initialized to zero during program startup. cpp int initializedVariable = 42; // Goes to the Initialized Data Section int uninitializedVariable; // Goes to the BSS Section

Main Memory