Intro to Computer Programming and Problem Solving

Computer Programming

• Computer programming involves instructing computers to perform specific tasks or solve problems.
• It represents collaboration between humans, who create instructions, and computers, which follow them.
• Programming involves giving commands to a computer, like printing or multiplying numbers.
• A computer program is a sequence of commands.
• Program code, also known as source code or just code, is the form that computer programs take.
• Computer programs are sequences of commands written in a programming language.

Problem Solving

• Creativity and problem solving are critical in computer programming.
• A structured process is needed to identify problems and generate creative solutions before programming.
• Steps in problem solving:
  • Analyzing the problem: Identify the problem, required inputs, and desired output.
  • Developing an algorithm: Write an algorithm describing the step-by-step process to solve the problem, which is integral to planning.
  • Coding: Utilize high-level languages to write code based on the algorithm.
  • Debugging and testing: Ensure the software meets business and technical requirements and functions as expected, this rectification process continues until all errors are removed.

Algorithm

• An algorithm is a finite sequence of steps to complete a task and get the desired output.
• To arrange numbers in ascending order, an algorithm finds the smallest, prints it, and repeats.
• An algorithm must meet certain specific properties.
• Algorithms must take zero or more values as Input.
• Algorithms must produce at least one output value, from a specified set of input values, as the solution.
• Finiteness: Algorithms must end after a limited number of steps, leading to a solution.
• Definiteness: Algorithms must have clear and unambiguous steps.
• Effectiveness: An algorithm should consistently produce meaningful, correct results with valid, basic operations that can be done manually.
• Algorithms must be language-independent, implementable in any language with consistent output.
• Steps for writing out algorithms:
  • Define the input; circle perimeter calculations use the radius of the circle.
  • Define variables to store inputs, constants, intermediate results and final output; radius for the circle's radius and pi for π, approximately 3.14159.
  • Outline operations, for calculating a circle's perimeter, multiply the radius by 2*pi, and store the result in a new variable.
  • Output the operation results, for a circle with a radius of 2, the algorithm would output 12.56636.
• Variables are used when writing an algorithm.
• Variables are named memory spaces which are to store values.
• Variables stores input values as well as the results of mathematical operations.
• Rules for naming variables:
  • No spaces.
  • No keywords.
  • The name should be relevant.
• Arithmetic operators used in algorithms:
  • + for addition. Example: A + B
  • - for subtraction. Example: A - B
  • * for multiplication. Example: A * B
  • / for division. Example: A / B
  • ^ for power. Example: A ^ B
  • % for remainder. Example: A % B
• Comparison/relational operators used in algorithms:
  • > Greater than: A > B
  • < Less than: A < B
  • = or == Equal: A = B or A == B
  • >= Greater than or equal to: A >= B
  • <= Less than or equal to: A <= B
  • <> or != Not equal: A <> B or A != B
• Logical operators manipulate Boolean values (true/false) and return a Boolean result based on the operands' logical relationship.
  • AND: Both conditions must be true. Result is True if A < B AND B < C are true.
  • OR: Either condition must be true. Result is True if A < B OR B < C are true.
  • NOT: The condition must be reversed. Result is True if A > B is false.
• Three algorithm control structures:
  • Sequence: Statements placed one after the other, executed from top to bottom.
  • Selection (Branching): A condition dictates a TRUE or FALSE decision; if TRUE, one branch is followed, otherwise, the other is.
  • Loop (Repetition): Executes a statement/code block repeatedly based on a loop condition using WHILE or FOR loops that relies on logical tests.
• Two ways to represent an algorithm:
  • Pseudocode.
  • Flowchart.

Pseudocode

• Pseudocode is a non-formal language for writing algorithms without specific syntax.
• Each step is written in sequence on it's own line.
• Instructions are in uppercase, variables are in lowercase, and messages are written in sentence case.
• Commonly used keywords in pseudocode:
  • START – BEGIN to identify the starting point of a program.
  • OUTPUT – PRINT – DISPLAY to output the result.
  • IF/ELSE for control statements.
  • For – WHILE to repeat a set of statements.
  • STOP – END to identify the ending point of the program.
  • INPUT – READ – GET to accept input.
  • GO TO to transfer control of execution to another step/statement.
• There are two types of selection control statements.
• IF…. THEN …. ENDIF
  • If the condition is true, the statements between THEN and ENDIF are executed.
• IF…. THEN …. ELSE …. ENDIF
  • If the condition is true, statements between THEN and ELSE are executed or the statements between ELSE and ENDIF are executed.
• There are three types of repetition statements
• WHILE …. DO …. ENDWHILE
• Executes the loop as long as the condition is TRUE.
• REPEAT…. UNTIL
• Executes the loop as long as the condition is FALSE.
• FOR … TO …. NEXT executes a statement a known number of times.
  • A control variable is incremented by 1 each time the loop ends.
  • The loop repeats as long as this control variable is less than or equal to the final value it is set to.

Flowchart

• Flowcharts are visual representations of algorithms using shapes and arrows.
• Each shape represents a step, and arrows indicate the process flow.
• Flowcharts go from top to bottom.
• Flowchart Symbols:
  • Oval for Start/Stop (terminal symbol)
  • Arrows for flow direction
  • Parallelogram for Input/Output processes
  • Rectangle for processing/arithmetic operations
  • Diamond for decisions (True/False questions)
• There are two types of selection control statements.
  • IF…. THEN …. ENDIF
  • IF…. THEN …. ELSE …. ENDIF
• There are three types of repetition statements.
  • WHILE …. DO …. ENDWHILE
  • REPEAT…. UNTIL
  • FOR … TO …. NEXT

Example Pseudocode and Flowcharts

• Example 1. Calculate the Summation of Two Numbers:

  • Algorithm: Start, Input first Number, Input second Number, Compute the summation of entered numbers, Print the value of the sum, End.

• Pseudocode: 1.START, 2. INPUT num1 and num2, 3. COMPUTE sum = num1 + num2, 4. PRINT sum, 5. STOP.

• Example 2. Calculate the perimeter of a circle (Given the radius):

  • Algorithm: Start, Input the radius of a circle, Set pi = 3.14, compute perimeter = 2piradius, Print the value of perimeter, End.
  • Pseudocode: 1.START, 2. INPUT radius, 3. SET pi = 3.14, 4. COMPUTE perimeter = 2piradius, 5. PRINT perimeter, 6. STOP.

• Example 3. Calculate the area of a rectangle (Given Length and Width):

  • Algorithm: Start, Input the rectangle length as Length, Input the rectangle width as Width, compute the Area = length * width, Print the value of Area, End.
  • Pseudocode: 1.START, 2. INPUT length and width, 3. COMPUTE area = length * width, 4. PRINT area, 5. STOP.

• Example 4. Swap the values of the the two numbers.

  • Algorithm: Start, Input the first number, Input the second number, Set temp = num1, Set num1 = num2, Set num2 = temp, Print the values of num1 and num2, End.
  • Pseudocode: 1.START, 2. INPUT num1 and num2, 3. SET temp = num1, 4. SET num1 = num2, 5. SET num2 = temp, 6. PRINT num1 and num2, 7. STOP.

• Example 5. Find Whether the Given Number is Even or Odd.

  • Algorithm: Start, Input number, If the number is Divided by 2; Print number is Even or Otherwise Print Number is Odd, End.
  • Pseudocode: 1.START, 2. INPUT num, 3. IF (num % 2 ==0) THEN, PRINT num is even, 4. ELSE, PRINT num is odd, 5. ENDIF, 6. STOP.

• Example 6. Find Largest of Two Numbers.

  • Algorithm: Start, Input the first number and the second number, and comparing both numbers, If condition is satisfied Print the number and End.
  • Pseudocode: 1.START, 2. INPUT num1 and num2, 3. IF (num1 > num2) THEN; SET max = num1, 4. ELSE; SET max = num2, 5. ENDIF, 6. PRINT max, 7. STOP.

• Example 7. Find the Largest Number of Three Numbers

  • Algorithm: Initialize first to variables (num1, num2, num3); Input all variables required, compare each variable and set a if condition to satisfy which number if the greatest of all; If (num2 > max); Set Max = num2 and End the statement
  • Pseudocode: 1.START, 2. INPUT num1, num2, num3, 3. SET max = num1, 4. IF (num2 > max) THEN, SET max = num2, 5. ENDIF, 6. IF (num3 > max) THEN; SET max = num3, 7. ENDIF, 8. PRINT max, 9. STOP.