Lecture_3

Week 3

Control Statements

Jumagaliyev Assylbek

asylbek.jumagaliyev@gmail.com

Introduction

●Presenting the theory and principles of structured programming.

●Demonstration of the for, do...while and switch statements.

Essentials of Counter-Controlled

Repetition

Counter-controlled repetition requires

●the name of a control variable (or loop counter)

●the initial value of the control variable

●the loop-continuation condition that tests for the final value of the control variable (i.e., whether looping should continue)

●the increment (or decrement) by which the control variable is modified each time through the loop.

Counter-controlled repetition.

1. name

2. initial value

3. loop-continuation conditio

4. final value

5. increment (or decrement)

1 2 3 4 5 6 7 8 9 10

for Repetition Statement

●The while statement can be used to implement any counter-controlled loop.

●for repetition statement specifies the counter-controlled repetition details in a single line of code.

●To illustrate the power of for, we rewrite the previous program.

for Repetition Statement

1 2 3 4 5 6 7 8 9 10

for Statement Header Components

Notice that previous example uses the loop-continuation condition counter <= 10. If the programmer incorrectly wrote counter < 10, then the loop would execute only 9 times. This is a common off-by-one error.

while vs. for

The general form of the for statement is

for ( initialization; loopContinuationCondition; increment )

{

Statement;

}

The general form of the while statement is

initialization;

while ( loopContinuationCondition )

{

Statement;

Increment;

}

for Repetition Statement

The initialization, loop-continuation condition and increment expressions of a for statement can contain arithmetic expressions. For example, if x = 2 and y = 10, and x and y are not modified in the loop body, the for header

for ( int j = x; j <= 4 * x * y; j += y / x )

is equivalent to

for ( int j = 2; j <= 80; j += 5 )

Examples Using the for Statement

Vary the control variable from 1 to 100 in increments of 1.

for ( int i = 1; i <= 100; i++ )

Vary the control variable from 100 down to 1 in increments of -1 (that is, decrements of 1).

for ( int i = 100; i >= 1; i-- )

Vary the control variable from 7 to 77 in steps of 7. for ( int i = 7; i <= 77; i += 7 )