The Decision Control Structure

 

1. The Decision Control Structure The decision control structure allows a program to make a decision based on certain conditions. The decision structure in C is implemented using the if statement.

2. Decisions! Decisions! In programming, decision making is an essential element. The decision-making process involves evaluating one or more conditions and executing a set of statements based on the result of the evaluation.

3. The if Statement The if statement in C is used to execute a set of statements if a particular condition is true. The syntax for the if statement is as follows:

c
if (condition) { // Statements to execute if condition is true
}

For example:

c
int num = 5; 
if (num > 0) { 
    printf("The number is positive."); 
}

4. The Real Thing The if statement is a real control structure because it allows the program to make decisions based on specific conditions.

5. Multiple Statements within if Multiple statements can be executed within the if block by enclosing them in curly braces.

6. The if-else Statement The if-else statement is used to execute a set of statements if a condition is true, and another set of statements if the condition is false. The syntax for the if-else statement is as follows:

c
if (condition) {
    // Statements to execute if condition is true
} else {
    // Statements to execute if condition is false
}

For example:

c
int num = -5; 
if (num > 0) { 
    printf("The number is positive."); 
} 
else{ 
    printf("The number is negative.");
 }

7. Nested if-elses Nested if-else statements allow multiple conditions to be evaluated. For example:

c
int num = 0; 
if (num > 0) { 
    printf("The number is positive."); 
} 
else if (num < 0) { 
    printf("The number is negative."); 
} 
else { 
    printf("The number is zero."); 
}

8. Forms of if There are several forms of the if statement, including the if-else statement and the nested if-else statement.

9. Use of Logical Operators Logical operators, such as && (and), || (or), and ! (not), can be used to combine multiple conditions in a single if statement.

10. The else if Clause The else if clause allows multiple conditions to be evaluated in a single if statement. For example:

c
int num = 75;
if (num < 50) { 
    printf("The number is less than 50.");
 } 
else if (num < 100) {
    printf("The number is between 50 and 100.");
 } 
else { 
    printf("The number is greater than or equal to 100."); 
}

11. The ! Operator The ! operator is used to reverse the result of a condition. For example:

c
int num = 5; 
if (!(num > 0)) { 
    printf("The number is negative or zero."); 
} 
else { 
    printf("The number is positive."); 
}

12. Hierarchy of Operators Revisited The hierarchy of operators in C determines the order in which operations are performed. This hierarchy is important to understand when using logical operators in if statements.

13. A Word of Caution Using too many nested if statements can make code difficult to read and debug.

14. The Conditional Operators The conditional operator (?:) allows a single if-else statement to be written in a compact form. The syntax for the conditional operator is as follows:

syntex
(condition) ? expression1 : expression2;

c
int num = 5;
int result = (num > 0) ? 1 : 0;