Explain Selection control statements and Iteration statements in C plus plus?

Answer 1

Selection control statements in C++

There are basically two types of control statements in c++ which allows the programmer to modify the regular sequential execution of statements.They are selection and iteration statements. The selection statements allow to choose a set of statements for execution depending on a condition. If statement and switch statement are two statements which allow selection in c++. There is also an operator known as conditional operator which enables selection.

If statement

Syntax : if (expression or condition)

{ statement 1;

statement 2;

}

else

{ statement 3;

statement 4;

}

The expression or condition is any expression built using relational operators which either yields true or false condition. If no relational operators are used for comparison, then the expression will be evaluated and zero is taken as false and non zero value is taken as true. If the condition is true, statement1 and statement2 is executed otherwise statement 3 and statement 4 is executed. Else part in the if statement is optional. If there is no else part, then the next statement after the if statement is exceuted, if the condition is false. If there is only one statement to be executed in the if part or in the else part, braces can be omitted.

Following example program implements the ifstatement.

// evenodd.cpp

# include

# include

void main()

{

int num;

cout<<"Please enter a number"<

cin>>num;

if ((num%2) to compare whether remainder is equal to zero or not.

Switch statement

Nested ifs can be confusing if the if statement is deeply nested. One alternative to nested if is the switch statement which can be used to increase clarity in case of checking the different values of the same variable and execute statements accordingly.

Syntax :

Switch (variablename)

{ case value1: statement1;

break;

case value2: statement2;

break;

case value3: statement3;

break;

default: statement4;

}

Iteration statements in C++

Iteration or loops are important statements in c++ which helps to accomplish repeatitive execution of programming statements. There are three loop statements in C++ : while loop, do while loop and for loop

While loop

Syntax: while (condition expression)

{

Statement1;

Statement 2;

}

Do..while loop

The do while loop is same as while loop except that the condition is checked after the execution of statements in the do..while loop. Hence in do..while loop, statements inside the loop are executed atleast once. However, in while loop, since the condition is checked before, the statements inside the loop will not be executed if the loop condition is false.

Do..while Statement

Please note that there is no semicolon after do, but there is a semicolon after the condition expression in while part.