Operators and Control Flow in Programming Lecture 4

Operators and Control Flow

• Unary operators (+/-, ++, --) are common, but focus on their use, not on all variations
• Order of Operations (precedence) is crucial; use parentheses for clarity. Complex expressions should be avoided to improve readability.
• Control flow is the first real programming topic, involves changing program flow based upon a condition.
• Integer order of evaluation: Operators have a defined order of precedence (*, /, %, +, -). Use parentheses if needed to disambiguate expression evaluation.

Control Flow Examples

• if/else statements:
  • An if statement executes a block of code if a condition is true
  • Use else to specify an alternative block for when the condition is false
  • Indentation improves readability.
• if-else blocks:
  • if(condition) { statement1; statement2; }; else {statement 3;}
  • Only one block executes; statement2 only if condition is true.
• Example if structure:

if (age < 18) 
    if (age > 12) 
       printf("Teenager\n");  
    else
       printf ("Child\n");
else
    printf("Adult\n"); 

• Relational and logical operators are used in the condition.

Relational and Logical Operators

• Relational Operators: <, >, <=, >=, ==, != determine relationships between values. For example: x > 10.

• Logical Operators: && (AND), || (OR), ! (NOT) combine relational expressions.

  • Example: if (x > 10 && y < 20) ...

switch-case Statements

• Used to represent simple conditions.

switch (x) {
    case 1:
        printf("One\n");
        break;
    case 2:
        printf("Two\n");
        break;
    default:
        printf("None\n");
        break;
}

• break is crucial; without it, cases may "fall through."
• Cases should be constants.

Important Notes

• Readability: Write code that is easy to read and understand (use indentation).
• Error Prevention: Avoid complex expressions, and use parentheses for complex logical operations.
• Data Types: Ensure data types (int, char, enum) are consistent.