Programming Selection Control Structures

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Questions and Answers

What is a boolean expression?

An expression that represents a condition without a value.

An expression that has a value of true or false. (correct)

An expression that exclusively uses relational operators.

An expression that can only return numerical values.

Which of the following is a relational operator?

< (correct)

Which of the following expressions evaluates to true given int y=6 and int x=5?

y >= 6 (correct)

y > x (correct)

x != 5

y < x

What is the result of the expression !(x == 50) when int x = 50?

False Signup and view all the answers

In which scenario does the logical OR operator (||) yield a true value?

At least one operand is true. Signup and view all the answers

What is the result of the expression (x >= 10) || (x == 4) when int x = 4?

True Signup and view all the answers

What is the highest precedence operator among the following?

! Signup and view all the answers

What will be the result of the expression (y != z) || (z < x) when int x = 4, y = 5, z = 8?

True Signup and view all the answers

What is the main purpose of a selection control structure in programming?

To execute different sets of statements based on a condition Signup and view all the answers

Which of the following statements correctly describes the use of boolean values?

Boolean values indicate true as 1 and false as 0 Signup and view all the answers

Which of the following control structures allows for executing a set of statements continuously based on a condition?

Repetition Signup and view all the answers

What does an if statement do during its evaluation?

It evaluates a condition to determine which statements to execute Signup and view all the answers

What is the result of a condition that evaluates to false in a selection control structure?

The statements in statement set 2 are executed, if present Signup and view all the answers

Which of the following is NOT a type of control structure mentioned?

Iteration Signup and view all the answers

In the context of control structures, what does the term 'branch' refer to?

A situation where conditions lead to different execution paths Signup and view all the answers

Which of the following statements is true about conditional operators in programming?

They help in simplifying multiple conditional evaluations Signup and view all the answers

Study Notes

Selection Control Structures

Programs use control structures to control program flow.
Three types: sequential, selection, and repetition.

Sequential Control

A series of statements executed one after another.
Statements are executed in the order they appear.

Selection Control

Used to execute one set of statements if a condition is TRUE, a different set if FALSE, or no statements at all.
The program's flow depends on whether a condition is true or false.

Repetition Control

Used to execute a set of statements repeatedly as long as a given condition is TRUE.
The program keeps looping as long as the condition is true.

Learning Outcomes

Students should be able to explain selection control structures.
Students should be able to use relational and logical operators.
Students should be able to use if, if...else, if...else if, switch...case, nested if statements, and conditional operators.

Why Selection

Selection allows a program to choose an action based on a condition.
For example, password checks control user access.
Conditions need to be TRUE or FALSE.

Boolean Values

Boolean expressions are used for conditions.
TRUE is assigned 1; FALSE is 0.

Boolean Expressions

Relational operators make comparisons.
Logical operators combine relational expressions.
Relational and logical expressions are boolean expressions.

Relational Operators

Used to compare two values.
Examples: <, <=, >, >=, ==, !=
Examples using ints y = 6, x = 5 (y>x, T; y<2, F; x>=3, T; y<=x, F; x ==5, T; y !=6, F)

Logical Operators

Used to combine two or more relational expressions.
Examples: && (AND), || (OR), ! (NOT)
Truth table examples given for AND, OR, NOT operations

Operator Precedence

Arithmetic operators have higher precedence than relational ones, which are higher than logical ones.
Parentheses can be used to control order of operations.
Examples are provided for precedence in calculating expressions.

Boolean Expressions in Variables

Boolean expressions can be assigned to variables.
0 means FALSE; any other value means TRUE.

Checking Numeric Ranges

Used to test if a value is within a range (e.g., a valid grade).
Cannot use mathematical notation like 0 <= grade <= 100;

if Statement

Used for a single selection path.
Statements following condition execute conditionally.

if...else Statement

Used to create a two-way selection path.
One statement block for TRUE condition; another block for FALSE condition.

if...else if Statement

Used to create a multiple-path selection.
Statements are executed sequentially based on testing conditions.

Nested if Statements

One if statement inside another if or else statement.

Dangling else

The else is associated with the closest unmatched if

Switch...Case Statement

Used for multiple selection paths.
Each case corresponds to a possible value.
A default case is for unexpected input.
Requires cases to compare against a single value, (e.g., a number, or a choice represented by a letter)

Programs with menus of choices for the user.
Program execution is controlled by what the user selects from the menu.

Example Code

Various example code snippets illustrating use of different types of selection statements.

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Description

This quiz covers the fundamentals of selection control structures in programming. Students will explore how these structures allow for conditional execution of code based on specific criteria. Key concepts include if statements, else conditions, and logical operators.