Notes on Computer Programs, Languages, Algorithms, Pseudocode and Flowcharts

Computer Program

  • A set and sequence of instructions given to a computer, telling it what to do.

  • Also called software; instructions are program source code.

  • Computer Programming is also called program coding.

Types of Programs

  • Systems Programs: Keep hardware/software running (e.g., Operating Systems like Linux, Windows).

  • Application Programs: Used by people to get work done (e.g., Word Processor, Games).

  • Compiler: Translates code into machine language (ones and zeros).

Programming Language

  • A standardized communication technique for expressing instructions to a computer, with its own syntax and grammar.

  • Enables a programmer to specify data, storage, and actions.

Common Programming Languages

  • Python — Artificial Intelligence & Machine Learning

  • JavaScript — Rich Interactive Web Development

  • Java — Enterprise Application Development

  • C/C++ — Operating Systems and System Tools

  • C# — Application & Web Development Using .NET

  • PHP — Web Development

  • SQL — Data Management

Computer Programmer and Types of Programmers

  • Someone who can write computer programs.

  • Types: Software Developers, Game Programmers, Software Engineers, Data Developers, Web Developers, Network System Administrators.

Coding and Debugging; Program Development Life Cycle (PDLC)

  • Core activities in software creation.

  • Compile-Time Errors: Syntax errors detected by the compiler (e.g., missing semicolon). Program won't compile.

  • Runtime Errors: Errors that occur while the program is running, after successful compilation (e.g., logic errors, infinite loops).

Categories of Programming Language

  • High-level Programming Languages: User-friendly, somewhat platform-independent, abstract from low-level operations. A statement translates to one or several machine instructions via a compiler. Examples: Java, C, C++, Python.

  • Low-level Assembly Language: Closer to machine language; uses symbolic names instead of numbers. Translated by an assembler and specific to each CPU family.

High-Level vs Low-Level Language (Analogies)

  • High-Level Language (e.g., Python): Like speaking human language; easy-to-read instructions. \texttt{print("Hello")}

  • Low-Level Language (Assembly): Detailed, robot-like instructions, closer to the computer's native tongue.

  • Analogy: High-Level = Ordering at a fast-food restaurant (easy); Low-Level = Cooking it yourself (manage all details).

Algorithm

  • A step-by-step procedure to resolve a problem; a finite set of well-defined instructions.

  • Emphasizes a replicable process (Algorithmic thinking).

  • Elements: Input, Set of rules/steps, Output.

  • Representation: Input $\rightarrow$ (processing steps) $\rightarrow$ Output.

Pseudocode

  • Informal way of describing an algorithm using plain English mixed with programming-style keywords, without strict language syntax.

Flowcharting

  • A design tool to graphically represent solution logic or an algorithm pictorially.

Flowchart Symbols

  • Terminator: Start/End.

  • Process: An operation.

  • Document: Printout.

  • Decision: Branching point (diamond).

  • Data: Input/Output.

  • On-Page Reference: Flow continues on same page.

  • Off-Page Reference: Flow continues on different page.

  • Delay or Bottleneck: Identifies a delay.

  • Flow: Lines for sequence and direction.

Guidelines for Preparing a Proper Flowchart

  • Must be neat, easy to follow, with a logical start and end.

  • Include necessary steps in logical order.

  • Only one flow line from a process symbol.

  • Decision symbol: one incoming, two or three outgoing flow lines.

  • Terminal symbols: one flow line.

  • Symbols should clearly contain information.

  • Reduce flow-lines using connectors