CHAPTER 5: SELECTION STRUCTURES: if and switch STATEMENTS Prepared By: Pn. Nik Maria Nik Mahamood Reference: Hanly, Koffman, C Problem Solving and Program Design in C, Sixth Edition, Pearson International Edition. Refer chapter 4 (Pg. 178 – 240) INSPIRING CREATIVE AND INNOVATIVE MINDS DDC1012: PROGRAMMING

SELECTION STRUCTURES: if and switch STATEMENTS 5.1Control Structures 5.2Conditions 5.3The if Statements 5.4If Statements with Compound Statements. 5.5Nested if Statements and Multiple-Alternative Decisions 5.6Decision Steps in Algorithms 5.7The switch Statement INSPIRING CREATIVE AND INNOVATIVE MINDS

Control structures – control the flow of execution in a program. Control structures - individual instructions into a single logical unit with one entry point and one exit point. Instruction are organized into three kinds of control structures to control execution flow: –Sequence –Selection –Repetition. Compound statement – a group of statements bracketed by { and } that are executed sequentially. INSPIRING CREATIVE AND INNOVATIVE MINDS 5.1 CONTROL STRUCTURES

Example: { statement1; statement2; … statementN; } A selection control structure chooses which alternative to execute. INSPIRING CREATIVE AND INNOVATIVE MINDS 5.1 CONTROL STRUCTURES

This topic already covered in chapter 4. You can refer this topic at page (Main TextBook). INSPIRING CREATIVE AND INNOVATIVE MINDS 5.2 CONDITIONS

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.3 THE if STATEMENTS if Statement with one alternative –Syntax as follows: If (condition) statements; –Example #1 if (x != 0.0) product = product * x; –Example #2 if (k < j) min = k; prinf(“Akhir kenyataan if\n”); will be executed if k < j Always be executed even k >= j

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.3 THE if STATEMENTS If statement with two alternatives – Syntax as follows: if (condition) statement; else statement; – Example if (rest_heart_rate > 56) printf(“Keep up your exercise!\n”); else printf(“Your heart is in execllent health!\n”);

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.4 if STATEMENTS WITH COMPOUND STATEMENTS Example #1 if (k < j) { min = k; prinf(“END if STATEMENT\n”); } Example #2 Source: This figure is taken from Pearson Addison-Wesley, 2009

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.4 if STATEMENTS WITH COMPOUND STATEMENTS Example #3 (Taken from Example 4.13 page 195) if (ctri < = MAX_SAFE_CTRI) { printf(“Car #%d: Safe\n”, auto_id); safe = safe + 1; } else { printf(“Car #%d: unsafe\n”, auto_id); unsafe = unsafe + 1; }

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.5 DECISION STEPS IN ALGORITHM Decision step – an algorithm step that selects one of several actions. Refer Case study : water Bill Problem (See page 198 – 206)

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.5 DECISION STEPS IN ALGORITHM Figure 4.6 Structure Chart for Water Bill Problem Source: This figure is taken from Pearson Addison-Wesley, 2009.

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.5 DECISION STEPS IN ALGORITHM Figure 4.7 Program for Water Bill Problem Source: This figure is taken from Pearson Addison-Wesley, 2009.

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.5 DECISION STEPS IN ALGORITHM Figure 4.7 Program for Water Bill Problem Source: This figure is taken from Pearson Addison-Wesley, 2009.

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.5 DECISION STEPS IN ALGORITHM Figure 4.7 Program for Water Bill Problem Source: This figure is taken from Pearson Addison-Wesley, 2009.

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.5 DECISION STEPS IN ALGORITHM Figure 4.7 Program for Water Bill Problem Source: This figure is taken from Pearson Addison-Wesley, 2009.

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.5 DECISION STEPS IN ALGORITHM Figure 4.8 Sample Run of Water Bill Program Source: This figure is taken from Pearson Addison-Wesley, 2009.

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.6 NESTED if STATEMENTS AND MULTIPLE ALTERNATIVES DECISION  Nested if statements – an if statement with another if statement as its true task or its false task.  Example: if (x > 0) num_pos = num_pos + 1; else { if (x < 0) num_neg = num_neg + 1; else num_zero = num_zero + 1; }

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.6 NESTED if STATEMENTS AND MULTIPLE ALTERNATIVES DECISION  Multiple – Alternative Decision form of nested if: if (x > 0) num_pos = num_pos + 1; else if (x < 0) num_neg = num_neg + 1; else if num_zero = num_zero + 1;

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.6 NESTED if STATEMENTS AND MULTIPLE ALTERNATIVES DECISION  For more exercises, see - Example 4.16 at page Example 4.17 at page Example 4.18 at page Example 4.19 at page

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.7 THE switch STATEMENTS  The switch statement may also be used in C to select one of several alternatives.  Used expression in implementation. This expression also known as controlling expression  The value of this expression may be of type - char - int

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.7 THE switch STATEMENTS  Question taken from example 4.20 at page 222  Using switch statements to implement the following requirement: Class IDShipp Class B or bBattleship C or cCruiser D or dDestroyer F or fFrigate

INSPIRING CREATIVE AND INNOVATIVE MINDS 5.7 THE switch STATEMENTS Figure 4.12 Example of a switch Statement with Type char Case Labels Source: This figure is taken from Pearson Addison-Wesley, 2009.