GEC 114 - Largest Integer Algorithm

GEC 114 - Applications of Information and Communication Technology

• Course: GEC 114
• Topic: Applications of Information and Communication Technology
• Lecture: 11
• Subject: Algorithms (Pseudocode)
• Instructor: Sameer Akram Mirza
• Semester: Fall 2024

Finding the Largest Integer

• Example: Finding the largest integer among five integers (12, 8, 13, 9, 11)
• Steps in the FindLargest algorithm:
  • Set Largest to the first number in the list.
  • Compare the second number to Largest. If the second number is larger, update Largest.
  • Repeat this comparison for the third, fourth, and fifth numbers in the list.
  • The final value of Largest is the largest integer in the list.

Defining Actions in FindLargest Algorithm

• Step-by-step description of the FindLargest algorithm.

Properties of Algorithm

• Finiteness: The algorithm must complete after a finite number of steps.
• Absence of Ambiguity: Each step must have a clear, unambiguous interpretation for the computer.
• Sequence Definition: Steps must be clearly ordered.
• Input and Output Definition: The algorithm must specify what input data it needs and what output it will produce.
• Effectiveness: All instructions must be achievable by the computer in a reasonable amount of time.
• Scope of Definition: The algorithm must be applicable to a specific problem or class of problems.

Properties of Algorithm (Continued)

• Finiteness: The algorithm must end after a fixed, finite number of actions.
• Absence of Ambiguity: All steps must be clear to the computer; no room for interpretation.
• Examples of notational detail include pseudocode and flowcharts.

Properties of Algorithm (Continued Two)

• Sequence Definition: Steps are performed in a predefined order, typically from top to bottom unless otherwise indicated.
• Input and Output Definition: The algorithm precisely defines input (data the algorithm receives) and output (result the algorithm produces).
• Input: Data the algorithm takes as a parameter or from an external source.
• Output: Result or data the algorithm produces.

Properties of Algorithm (Continued Three)

• Effectiveness: Algorithm steps must be realizable, meaning the instructions can be carried out using available resources.
• Scope of Definition: Algorithm application's limits; problem type or input range.

How to Express an Algorithm

• Algorithms can be expressed in different ways:
  • Natural language
  • Pseudocode
  • Flowcharts
  • Programming languages

What is Pseudocode

• "Pseudo" means artificial or imitation.
• "Code" refers to instructions akin to a programming language.
• Pseudocode acts as a planning tool for programs.
• It's often called Program Design Language (PDL).

What is Pseudocode (Continued)

• A high-level, informal description of an algorithm.
• Uses programming language structure for human readability, not machine execution.

Pseudocode Statements and Flowchart Symbols

• Flowchart: A pictorial representation of algorithm steps.
• Pseudocode: A language-like way to describe algorithm steps.
• Pseudocode closely resembles high-level programming language statements.

Logical Structure of Pseudocode

• Pseudocode utilizes logic structures, shown to be sufficient for structuring computer programs:
  • Sequence logic
  • Selection logic
  • Iteration logic

Sequence Logic

• Sequence logic executes steps in a linear order, one after the other.
• In pseudocode, instructions are written in the order they should be executed.

Sequence Logic (Continued)

• Shows a flowchart and corresponding pseudocode for sequence logic using steps.

Selection Logic

• Selection logic makes decisions ("if-then") to determine the execution path.
• Common forms include IF...THEN and IF...THEN...ELSE structures

Iteration Logic

• Iteration logic, or looping, allows for repeated execution based on certain conditions until a condition is met.
• It uses structures like DO-WHILE, FOR, and REPEAT-UNTIL.

Rules for Pseudocode

• One statement per line: Each line describes one action.
• Capitalized initial keywords: Key words like READ, WRITE, IF, ELSE, etc., start with a capitalized letter.
• Indentation: Use indentation to show the blocks of code within the logic structures.
• End multi-line structures: Correspond to beginning keywords (like IF , THEN) with ending keywords (LIKE ENDIF)
• Language independent: Write pseudocode in a way that is readable and understandable regardless of the programming language.

Rules for Pseudocode (Continued)

• Examples of tasks and pseudocode using rules; task lists and pseudocode examples.

Rules for Pseudocode (Continued Two)

• Ending keywords correspond to starting keywords
• Pseudocode language is independent of programming language

Standard for Good Pseudocode

• Each instruction must be numbered; well-ordered, unambiguous, and effectively computable.
• Pseudocode must be complete.

Advantages of Pseudocode

• Converting pseudocode to a programming language is easier than converting a flowchart.
• Modifying program logic within pseudocode is simpler than in a flowchart.

Limitations of Pseudocode

• Pseudocode lacks a graphical representation for program logic.
• There are no standard rules for pseudocode, leading to different styles and communication challenges.

Presentation Conclusion

• Summary and conclusion of the presentation on pseudocode.