PRESENTED BY

Asstt. Prof Mandeep KaurComputer Dept

TOPIC: Control Statements in C language

Control statements are used to change the order of execution of the statements. These are divided into three parts as :

Branching(Selective)Statements The if statement The else-if statement The else-if construct The nested if statement The switch statementLooping Statements The for statement The while statement The do-while statementJumping(Breaking control)Statements The break statement The continue statement The goto statement

Decision Statements in C

The statements used to alter the flow of the program are known as decision statements.

These are used to check that whether the particular statement is true or not. Following is the list of decision statements often used:

1. The if Statement:   Explanation: if the test expression is true, then statement-block will

execute,otherwise it will jump to statement-x.

Syntax of if Statement:if (test expression) { statement –block; } statement-x;

//Program to implement if statement#include<stdio.h> #include<conio.h> void main() { clrscr(); int a,b,big; printf("Enter two numbers\n"); scanf("%d%d",&a,&b); big=a;if(big>b)big=b; printf("%d is greater",big); getch(); } 

2. The if-else statement: It is a two way branching statementExplanation: if the test condition is true, then true-block

statements will execute otherwise false-block statements will execute.

Syntax for if-else statement if (test expression){ True-block statement (s); } else { False-block statement(s); }

//Program to implement if else statement #include<stdio.h> #include<conio.h> void main() { clrscr(); int year; printf("Enter year\n"); scanf("%d",&year); if(year%4==0) printf("leap year"); else printf("not a leap year"); getch(); }

3.Nested if statements:

When an if statement appers within anoter if statement, the statement is called nested if statement.

SyntaxIf<expression-1>If(expression-2)<Statement-set-1>Else<Statement-set-3>If(expression-3)<Statement-set-3>ElseIf<Statement-set-4>

Program to implement the use of nested if statement. Void main() {

int a,b,c; printf(“Enter three integer numbers”); scanf(“%d%d%d”,&a,&b,&c); if(a>b) { If(a>c) printf(“|nGreatest number=%d”,a); else printf(“|nGreatest number=%d”,c); } else { If(b>c) printf(“|nGreatest number=%d”,b); else printf(“|nGreatest number=%d”,c); } getch(); }

4. The if-else-if ladder Explanation: as soon as the true condition is found the statement associated with it is executed and the control is transferred to statement-x. When all the n conditions become false the default statement will be executed.

if(condition 1) statement -1; else if(condition 2) statement -2; else if (condition 3) statement-3; ……………… ……………………………… ……………… else if(condition n) statement-n; else default-statement;

//Program to show use of if-else-if ladder #include<stdio.h> #include<conio.h> void main() { clrscr(); int day; printf("Enter number between 1-7\n"); scanf("%d",&day); if(day==1) printf("Monday"); else if(day==2) printf("Tuesday"); else if(day==3) printf("Wednesday"); else if(day==4) printf("Thursday"); else if(day==5) printf("Friday"); else if(day==6) printf("Saturday"); else if(day==7) printf("Sunday"); else printf("Enter correct no"); getch(); }

4. The switch statement Syntax switch(expression) { case 1: statement -1; break; case 2: statement -2; break; case 3: statement -3; break; ….….. …………case n: statement -n; break; default: statement; } statement-x;

//Program to implement switch statement #include<stdio.h> #include<conio.h> void main() { clrscr(); int x; float a,b; printf("Enter first no\n"); scanf("%f",&a); printf("Enter second no\n"); scanf("%f",&b); printf("@@@@@@@@@@@@@@@@@@@@@@@\n");

printf("Algebric Operations\n"); printf("@@@@@@@@@@@@@@@@@@@@@@@\n");

printf("1. summation\n"); printf("2. difference\n"); printf("3. Product\n"); printf("4. Diviosion\n"); printf("@@@@@@@@@@@@@@@@@@@@@@@\n"); printf("Enter the no as per required\n");

printf("@@@@@@@@@@@@@@@@@@@@@@@\n"); scanf("%d",&x); switch(x) {

case 1: printf("Sum=%.2f",a+b); break; case 2: printf("Differene=%.2f",a-b); break; case 3: printf("Product=%.2f",a*b); break; case 4: printf("Division=%.2f",a/b); break; default: printf("Enter correct no"); break; } getch(); }

Loop Control Statements in C

A Loop is a block of statements which are repeatedly executed for certain number of times. Steps in Loop

 a) Expression 1: Initialization e.g. if i is any variable then

in this we have to start the variable. Let us say i=1  b) Expression 2: Test Condition in this the condition is

checked again and again. And if this condition satisfies then it will execute further otherwise not. Let us say i<=5.

 c) Expression 3: Increment or Decrement in this the

value is either increased or decreased in each step. Let us say i++.

Following are the loops used in C Language: for loop syntax for(expression-1; expression-2;expression-3) statement;

while loop syntaxexpression-1; while(expression-2) { statement; expression-3; } 2.The condition is tested before executing the body of the

loop. 3.Body of while loop is executed only if the condition is true. 

do- while expression-1; do { statement; expression-3; } while(expression-2);2.The condition is tested after executing the body of the

loop.3.Body of the do loop is executed at least once even if the

condition is false.

//Program showing use of for loop

#include<stdio.h> #include<conio.h> void main() { int x,i; clrscr(); printf("Enter any natural no\n"); scanf("%d",&x); for(i=1;i<=x;i++) printf("I=%d\n",i); getch(); }

//Program showing use of while loop

#include<stdio.h> #include<conio.h> void main() { clrscr(); int n=1; while(n<=10) { printf("\n%d",n); n++; } getch(); }

//Program showing use of do while loop

#include<stdio.h> #include<conio.h> void main() { clrscr(); int n=1; do { printf("\n%d",n); n++; } while(n<=10); getch(); }

Jumping Statements:

break statement:-The break statement is used to terminate loop or to exit from switch case structure. The break can be used within a for loop, a while loop, a do-while loop or a switch statement to transfer the control out of the block/loop. The statements enclosed in a pair of braces is called a block.

Syntaxbreak;

when break statement is encountered within the loop/block the control the control is transferred to block/statement immediately following loop/block, that is, loop is terminated.

// Program showing use of break statement.

Void main() { int i,j; clrscr(); for(i=1;i<=2;i++) { for(j=1;j<=2;j++) {

if(i==j) break; printf(“\n%d %d\n”i,j); } } }

The continue statement

The continue statement can be used within a while , a do-while or a for statement. The continue statement transfers the control to the beginning of the loop, for next iteration, after by passing the statements which one yet executed.

Syntaxcontinue;

// Program showing use of continue statement.

Void main() { int i,j; clrscr(); for(i=1;i<=2;i++) { for(j=1;j<=2;j++) {

if(i==j) continue; printf(“\n%d %d\n”i,j); } } }

The goto statement

The goto statement is used to alter the normal executin of program execution by transferring control to and other point of the program.

Syntaxgoto label;

where label is an identifier used to label the target statemnt to which control will be transferred. The target statement must be labelled and the lebel must be followed by a colon.

label : statement

a)unconditional goto statement:The unconditional goto statement is used to transfer the control from one part of the program to the other part without checking any condition.Normally prefered to use the unconditional goto statement in program as it may lead to a very complicated problem like an infinite loop.

  // Program showing use of unconditional goto statement.Void main(){start:printf(“I am doing MCA”);goto start;}

b)conditional goto statement: The conditional goto statement is used to transferthe control of the execution from one part of the program to the other. This transfer of control is based on certain condition.

// Program showing use of conditional goto statement. Void main() { int n=10; clrscr(); loop: printf(“%d”,n); n--; if(n>0) { goto loop; printf(“FIREEEEEE”); } }