Chapter 4 C Program Control

Size: px

Start display at page:

Download "Chapter 4 C Program Control"

Harry Singleton
7 years ago
Views:

1 Chapter 4 C Program Control

2 Objectives of this chapter: Repetitions will be considered in greater detail for.. repetition do while repetition Also multiple selection switch case statement will be learned. All these are called as program control statements Usage of break and continue statements in the program control statements. break continue Usage of logical operators (AND OR) for combining conditions

3 Repetition Essentials: Most of the programs involves repetitions or looping. The instructions placed in a loop executed repeatedly while the condition of repetition remains true. There are two types of repetitions as mentioned in Chap 3 Counter controlled repetitions Sentinel controlled repetitions

4 Example: Counter-Controlled Repetitions The following program prints out integer numbers from 1 to 10. Page 131 This program can be also written easily using for repetition Notice that the starting value and end value for the counter is known.

5 Page 132 All counter-controlled repetitions can be handled by using for repetitions

6 Example: Rewrite the program that produces the following output using for repetition.*

7 Example - Sum of Even Numbers: for Repetition Write a C program that determines the sum of the even numbers from 2 to 100. * Page 136

8 Chapter 3 Exercise - Page 124 We have already answered this program using counter-controlled repetition with while statement. Let s now rewrite this program using for repetition statement.

9 Switch.. Case Statements: Multiple Selection Statements Page 139 As an alternative to if.. else when dealing with multi-branching in C programming is the switch case controls. This statement also known as multiple choice statements. C-Syntax: switch ( test ) { case 1 : // Process for test = 1... break;. case 5 : // Process for test = 5... break; default : // Process for all other cases.... } Flow-Chart:

10 Example: Using Switch Case Statement Write a C program that reads 10 letter grades for a quiz results. Then writes out the sum of the each letter grades as shown below. The terminal output of the program should look as below when executed. The program s output should look like as follow: Page 140

11 Page 145 Do while is another type of repetition statement used in C. It is similar to while repetition while Repetition: Loop condition is tested at the beginning of the loop do While Repetition: Loop condition is tested at the end of the loop C-Syntax: C-Syntax: while (condition) do { { instructions instructions } } while (condition);

12 Example: Using Do While Repetition Write a C program that prints out the numbers from 1 to 10. The output of the program should be as shown below. * Page 146

13 Page 146 break and continue statements are used to alter the flow of the program. break: Break statement in a switch case used to skip remainder of statement. Break also can be used in repetition statements. The break statement are used to escape early from a repetition/loop. So if break statement used in a repetition it terminates the loop immediately. * Page 147

14 Page 147 break and continue statements are used to alter the flow of the program. continue: the continue usually used in repetition statements to skip the rest of the actions. Unlike break statements terminating the repetition, it only skips the rest of the actions. * Page 147

15 Page 147 So far we have studied programs including simple condition e.g. relation and equality operators (<, >, <=, <=, ==, and!=). C and other programming languages also provides (AND and OR) logical operators to form more complex conditions by combining simple conditions. C-Syntax && : is AND logical operator. : is OR logical operator. Logical operators are written between the simple conditions to be combined Condition1 && Condition2 : two conditions combined with AND Condition1 Condition2 : two conditions combined with OR Example: If ( x > 99 && x <= 999 ) printf( This is a three digit positive integer ); If (x > 0 && y > 0) printf ( This vector is in first quadrant. ); If (gender == 1 && age > 65) seniorfemale++;

16 TRUTH TABLES FOR LOGICAL OPERATORS ( && and ) The outcome of a simple condition in C is 1 for true and 0 for false. Then if or any repetition is executed upon this output value. x==4 gives 1 if true or gives 0 if false. Tables below shows all possible input values of 0 or 1 and output values for && and II operators. These tables are called truth tables. Example: int x=123; if ( x > 0 && x <= 999 ) printf( This is a three digit positive integer ); Question: What happens if we write x==4 in a line rather then x=4? What happens if we write if (x=4) instead of x==4?

17 Page 146

18 Page 162

19 Page 166 Below is the output of the program when executed: Sum of the 5 values is 1500 Or another output of the program when it is executed for only 3 values Sum of the 3 values is 310

20 Below is the output of the program when executed: Enter the number of integers to be processed: 5 Enter an integer: 372 Enter next integer: 920 Enter next integer: 73 Enter next integer: 8 Enter next integer: 3433 The smallest integer is: 8 Page 167

21 Below is the output of the program when executed: Product of the odd integers from 1 to 15 is: Page 167

22 Page 167 Below is the output of the program when executed: N N!

23 Page 169

9 Control Statements. 9.1 Introduction. 9.2 Objectives. 9.3 Statements

9 Control Statements. 9.1 Introduction. 9.2 Objectives. 9.3 Statements 9 Control Statements 9.1 Introduction The normal flow of execution in a high level language is sequential, i.e., each statement is executed in the order of its appearance in the program. However, depending