Program Logic - Belgium Campus iTversity

• Program Logic for Belgium Campus iTversity

Objectives

• Study objectives include IPOs, understanding logic, expressions, program control structures, sequence, selection, repetition, and combination in programming.

Program Design - IPO (Input -> Process -> Output)

• A well-structured program design should be created before diving into a problem.
• An Input, Process & Output Chart can be used in the planning and design programs.
• The IPO chart visually illustrates and describes how data flows between input, processing, and output stages.
• Input can come from an end-user or another program.
• Processing involves converting data into useful information.
• Output can shown on a screen, a chart/graph, or stored in a database.

IPO Examples

• IPO charts display the flow of input, processing, and output.
• Example: To calculate the area of a room, the Inputs are Length and Width.
• The process is Area = Length * Width.
• The output is Area.
• For calculating new weekly pay, the inputs are current weekly pay and raise rate.
• The processing involves calculating the new weekly pay by multiplying the current weekly pay by the raise rate, then adding the weekly raise to the current weekly pay.
• The output is new weekly pay.

Program Logic

• Program logic involves precise, ordered steps to transform input into the desired output using expressions, sequences, selections, repetitions, or combinations.
• Correct program logic yields an accurate solution or desired output
• Problem Analysis Phase is essential to program logic
• Essential Steps in Problem Analysis are identifying the Output goal, the necessary Input data, and the transformations performed during Processing.

Processing

• Processing involves identifying the changes/transformations needed to convert input into the desired output.
• The different ways to process are:
  • Calculations using expressions.
  • Step-by-step instructions in a sequence.
  • Making choices using selection structures.
  • Repeating groups of statements.
• Precise input processing reduces logical errors.
• Logical Errors occur when a program runs without syntax errors but fails to produce the intended output.

Example of Logic Error

• Incorrect: totalAmount = fruitNamePrice + howMany
• Correct: totalAmount = fruitNamePrice * howMany

Expressions

• Expressions are formed when the desired output requires combining one or more inputs using operators.
• Inputs form the operands in the expression.
• Operands are the variables that operators act upon to achieve the desired output.

Expressions Example

• For the combination of Operators and Operands:
  • 2 * y + 5
  • Operators are * and +.
  • Operands are 2, y, and 5.

Types of Operators

• Operators are symbols that instruct the compiler to do mathematical or logical manipulations.
• Binary Operators: Use with two operands
  • Arithmetic.
  • Logical.
  • Comparison.
  • Assignment.
  • Conditional.
  • Bitwise.
• Unary Operators: Work with one operand
  • Increment.
  • Decrement.
• Ternary Operators: Work with three operands
  • Conditional Checking.

Arithmetic Operators

• Assume variable A holds 10 and variable B holds 20
• + Adds two operands; A + B will give 30
• - Subtracts second operand from the first; A - B will give -10
• * Multiplies both operands; A * B will give 200
• / Divides numerator by de-numerator; B / A will give 2
• % Modulus Operator and remainder of after an integer division; B % A will give 0
• ++ Increment operator, increases integer value by one; A++ will give 11
• -- Decrement operator, decreases integer value by one; A-- will give 9

Relational Operators

• Assume variable A holds 10 and variable B holds 20
• == Checks if the value of two operands is equal or not. If yes, then condition becomes true; (A == B) is not true
• != Checks if the value of two operands is equal or not, if values are not equal then condition becomes true; (A != B) is true
• > Checks if the value of left operand is greater than the value of the right operand, if yes then condition becomes true; (A > B) is not true
• < Checks if the value of the left operand is less than the value of the right operand, if yes then condition becomes true; (A < B) is true
• >= Checks if the value of the left operand is greater than or equal to the value of the right operand, if yes then condition becomes true; (A >= B) is not true
• <= Checks if the value of the left operand is less than or equal to the value of the right operand, if yes then condition becomes true;(A <= B) is true

Logical / Boolean Operators

• Assume variable A holds 1 and variable B holds 0.
• && Logical AND operator, if both operands are non-zero, then condition becomes true; (A && B) is false
• || Logical OR Operator, if any of the two operands is non-zero, then condition becomes true; (A || B) is true
• ! Logical NOT Operator, reverses the logical state of its operand. If a condition is true, then Logical NOT operator will make it false; !(A && B) is true.

Assignment Operator

• = Simple assignment operator, assigns values from right side of operands to left side of the operand. C = A + B will assign value of A + B into C.
• += Add AND assignment operator, adds the right operand to the left operand and assign the result to left operand; C += A is equivalent to C=C+A
• -= Subtract AND assignment operator, subtracts right operand from the left operand and assigns the result to left operand; C -= A is equivalent to C=C-A
• *= Multiply AND assignment operator, multiplies right operand with the left operand and assign the result to the left operand; C = A is equivalent to C = CA
• /= Divide AND assignment operator, divides left operand with the right operand and assigns the result to the left operand; C /= A is equivalent to C = C/A
• %= Modulus AND assignment operator, it takes modulus using two operands and assign the result to left operand; C %= A is equivalent to C = C % A