Programming Methodology Notes

  • Introduction

    • Computer needs a programming language to function based on user instructions.
    • Programming language: Symbols, characters, grammar for human-readable commands.
    • Programming: Directing a machine.

  • Programming Language

    • Factors for selecting a language: company policy, task suitability, third-party packages, personal preference
    • Considerations: programmer availability, compiler availability, program efficiency
    • Basic instructions in programming languages:
    • Input, output, math, conditional execution, repetition
    • Examples of programming languages: ActionScript, ALGOL, Ada, Assembly, BASIC, C, C++, C#, COBOL, CSS, HTML, Java, PHP, Python, SQL.

  • Machine Level Language

    • Low-level language using binary digits (1s and 0s).
    • High-level languages are converted to machine language.
    • Computers understand binary data; programs/videos/images/text represented in binary.
    • ASCII "A" is 01000001 in machine code.
    • Different processor architectures use different machine code.
    • Machine code is the computer's basic language; circuitry understands and translates it.

  • Instruction format consists of command/procedure (tells machine what to do) and operand (specifies data location).

    • Common operations: reading, adding, subtracting, writing.
    • Machine language uses strings of binary numbers.

  • Advantages of Machine Language

    • Fast execution because instructions are directly understood by the CPU.

  • Limitations of Machine Language

    • Machine dependent: Differs for each computer due to internal design.
    • Difficult to program: Requires memorizing codes and tracking storage locations.
    • Error-prone: Complex and requires managing opcodes and storage.
    • Difficult to modify: Corrections or changes are complex and time-consuming.

  • Assembly Language

    • Second-generation languages that use alphabetic symbols instead of binary code.
    • Symbols are used for memory locations and mnemonics for operation codes.
    • Example: MOV AX, DX (MOV is mnemonic for ‘transfer’ operation).

  • Using letter symbols as mnemonics increases software planning.

  • Advantages of Assembly Language

    • Easier to use than machine language.
    • Assembler detects programming errors.
    • Programmers don't need absolute addresses.
    • Encourages modular programming.

  • Disadvantages of Assembly Language

    • Not directly executable.
    • Machine-dependent, not portable.
    • Requires high programming skill.

  • Assembly Program Execution

    • Assembly program is converted into machine code using an assembler.
    • Source program is converted to object program.
    • Steps include assembling (source .OBJ), linking (.OBJ to .EXE), and loading for execution.

  • Higher Level Languages

    • e.g., COBOL, FORTRAN, BASIC
    • High-level languages developed to simplify programming, using easier instructions.
    • Easier to understand compared to machine/assembly code.

  • Advantages of High-Level Languages

    • Readability: More readable than assembly and machine language.
    • Portability: Can run on different machines.
    • Easy debugging: Easier to remove errors.
    • Easy software development: Similar to natural languages.

  • Popular High-Level Languages: ADA, APL, BASIC, Pascal, FORTRAN, COBOL, C, LISP, RPG.

  • Characteristics of a Programming Language

    • Clarity, simplicity, and unity: Provides a conceptual framework and means of expressing algorithms.
    • Orthogonality: Changing one thing doesn't unintentionally affect another.
    • Support for abstraction: Bridges the gap between concepts and implementation.
    • Portability of programs: Easy to transfer programs.

  • Programming Environment : Provides utility and implemented easily with proper documentation and efficient testing

  • Reusability: Checked by program testing techniques like verification method

  • Algorithms

    • A step-by-step process to solve a problem, written in human-readable language.
    • Often written in pseudocode.

  • Characteristics of Algorithms

    • Clear and Unambiguous: Each step has one meaning.
    • Well-Defined Inputs/Outputs: Clearly defined inputs to be taken and outputs to be yielded.
    • Finiteness: Must be finite, not an infinite loop.
    • Feasible: Simple and practical with available resources.
    • Language Independent: Can be implemented in any language.

  • Advantages of Algorithms: Easier to understand; breaks down problems.

  • Disadvantages of Algorithms: Time-consuming to write; difficult to show branching and looping.

  • Flow Charts

    • Diagram representing steps and decisions in a process.
    • Useful for writing and illustrating programs.

  • Common Flowchart Symbols: Terminator, process, document, decision, data, on/off-page reference, flow lines, delay.

  • Programming Methodology

    • A method to solve complex problems using analysis, planning, design, and control.

  • Types of Programming Methodology

    • Procedural Programming: Procedures/code blocks perform tasks.
    • Object-oriented Programming: Revolves around entities/objects.
    • Functional Programming: Divides problems into functional units-logical units.