�

Class 3

Topic Covers

Control Statements

Control Statements are mainly divided into three.

Conditional Expressions: The conditional expressions are mainly used for decision making. The following statements are used to perform the task of the conditional operations. if statement

if-else statement nested if statement else-if Ladder switch statement

Loop Statements: The loop statements are essential to construct systematic bllock styled programming. In C, three various ways one may define the control structures using different types of loop operations. The following are the loop structures in C.

while loop do-while loop for loop

Breaking control statements/Jump statements: For effective handling of the loop statements, C allows the use of the following 3 types of control break statements.

Break Statement Continue Statement goto statement

if statement in C

if statementThe if statement is used to write conditional expressions. If the givencondition is true then it will execute the statements. Otherwise it willexecute optional statements.syntax:if<conditon>{ ----- -----} The expression is evaluated and if it is "true", the statement following theif is executed. In case the given expression is "false", the statement is skipped and execution continues with the next statement.

example:/*EXAMPLE 1: Even Number Odd Number Checking in C*//*EXAMPLE 2: Comparing 2 Numbers Using Simple if Condition in C*/

if-else statement in C if-else statementThe if-else statement is used to write conditional expressions. If the givencondition is true then it will execute the statements. Otherwise it willexecute else block statements.

syntax:

if<conditon>{ ----- -----}else{ ----- -----}

The expression is evaluated and if it is "true", the statement following theif is executed. In case the given expression is "false", the statement . under else block will be executed.

example:/* EXMAPLE 3: Leap Year Using Simple if-else Condition in C*/

nested if statement in C

The if statement within if statement is nested if.syntax:if(condition-1){ if(condition-2) { statement-1 }} else statement-2

if the condition-1 is satisfied, then only it checks the condition-2. Otherwise else block will be executed.

example:/*EXAMPLE 4 : big no among three numbers*/

else-if Ladder

else-if ladder statement formatif(condition-1) statement-1else if(condition-2) statement-1else statement-2

example:

/* EXAMPLE 5 : Biggest Number Among 4 Numbers*/

Switch statement in C

The switch statement is a multiway decision maker that tests whether an expression matches one of the number of constant values, and braces accordingly.

syntax: switch(expression) {

case constant1: statement; break; case constant2: statement; break; . . case constantn: statement; break; default: statement; }

* The expression whose value is being compared, may be any valid expression including the value of the variable, an arithimatic expression, logical comparision, a bitwise expression or the return value from a function call, but not the floating point expression.

* The constants in each of the case statements must obiviously be of the same type.

* The expression value is checked against each of the specified cases and when a match occurs, the statement following that is executed. Again to maintain generality, the statement can be either a simple or a compound statment.

* The value that follows the keyword case may only be constants they can't be expressions. They may be integers or characters, but not floating point numbers or character strings.

* The last case of this statement which is called the default case is optional and should be used according to the program's specific requirement.

* Execution or the switch constant in C follows this logic. No statements are executed until a case has been matched or the default case has been encountered.

example:/*EXAMPLE 6 Menu Driven Program For Arithematic Operations*/

While Loop

The while loop is used when we are not certain that the loop will be executed.After checking whether the initial condition is true or false and finding it to be true, only then the while loop will enter into the loop operations.

syntax:For single conditionwhile<condition> statement;For a block of statementswhile<condition>{ statement-1; statement-2; ......}

* The condition cab be any valid expression including the value of a variable a unary or binary expression, or the value returned by a function. The statement can be a single or compound statement. The condition is actually test condition.

* The while loop does not explicitly contain the initilization or

incrementation parts of the loop. These two statements are normally provided by the programmers.

initial condition while(test condition) { statement-1 statement-2 change of initial condition }

EXAMPLE:

/*EXAMPLE 8: Printing first 10 natural no's using while loop*//* EXAMPLE 9:Printing Table using while loop*//*EXAMPLE 10:Finding Sum Of Digits Using While Loop*//*EXAMPLE 11:Amstrong Number Using While Loop*/

do-While Loop

The do-while loop is used whenever one is certain about a test condition, then the do-while loop can be used. As it enters into the loop atleast once and then checks whether the given condition is true or false. As long as the test condition is true, the loop operations or statements will be repeated again and again.

Syntax:do{ statement-1 statement-2 ----------}while(condition);

EXAMPLE:/* EXAMPLE 12 Menu driven program having the following options 1. Factorial of a number 2. prime number 3. Even number*/

for Loop

The for loop is most commonly used in C. This loop consists of three expressions. The first expression is used to initialize the index value, the second to check whether or not the loop is to be continued again and thethird to change the index value for further iteration.

Sometimes the oprations carried out by the while loop can also be done by using the for loop. Depending on the situation programmer can decide the loop.Syntax:for(exp1;exp2;exp3) statement;where expression-1 is the initialization of the expression or condition; expression-2 is the condition checked as long as the the given expression is true. expression-3 is the incrementer or decrementer to change the index value of the for loop variable.

EXAMPLE:/*EXAMPLE 13 Printing Number And its Squares Using For Loop*//* EXAMPLE 14 printing using for loop*/ 1

2 2 3 3 3 4 4 4 4 5 5 5 5 5/* EXAMPLE 15 printing using for loop*/

12345 2345 345 45 5

/* EXAMPLE 16 printing using for loop*/* * * * *

* * * * * * * * * *What are the differences between while and for loop?

Both while and for loops are iteration statements. The following are few differences between both loops.while loop*it's a generic loop* The while loop starts with the keyword while and valid condition and iterates until the specified condition has been satisfied.* The while loop endless loop.

for loop* it's a numeric loop* The for loop starts with the keyword for and iterates no.of times until the condition is true. * By using for loop we can stop the loop after some no.of iterations.

What are the differences between while and do-while loops?

while loop* The condition will be at the begining of the loop* The body of the loop will be executed after condition has been satisfied.* The body of the loop will be executed if and only if the condition is satisfied. do-while* The condition will be at the ending of the loop* condition will be terminated with the semicolon.* The body of the loop will be executed before conditon * The body of the loop will be executed at least once even if the condition is not satisfied

break statement

The break statement is used to terminate the control from the loop statements of the case-structure. The break statement is normally used in the switch-case loop and in each case condition, the break statement must be used. If not, thecontrol will be transfered to the subsequent case condition.syntax:break;

example:

main(){ int i=1;while(i<=10)

{

if(i==5)

{ break;}printf("%d\n",i);

i++;}

continue statement

The continue statement is used to repeat the same operations once again evenif it checks the error.syntax: continue;The continue statement is used for the inverse operation of the break statement.

example:

main(){ int i=1;while(i<=10)

{

if(i==5)

{ continue;}printf("%d\n",i);

}

}

goto statement

The goto statement is used to alter the program execution sequence by transfering the control to some other part of the program.syntax:goto label;

Here, label is the valid C identifier. There are 2 ways of goto statements * Conditional goto * Unconditional goto

UnConditional goto:The unconditional goto statement is just used to transfer the control from one part of the program to other part without checking any conditi

on.example:main(){ start: printf("Welcome to c world"); goto start;}Conditional goto: The conditional goto is used to transfer the control of the execution from one part of the program to the other in certain conditional cases.example:main(){ int value,i; i=0; while(i<=10) { printf("enter number:"); scanf("%d",&value); if(value<=0) { printf("Zero or -ve value found"); goto error; } i++; } error: printf("Input data error");}