CONTROL STATEMENTS
THE PROGRAMS ARE MAINLY MEANT FOR STORING AND MANIPULATING DATAS. PROGRAMS NEED TOOLS FOR PERFORMING REPETITIVE ACTIONS AND FOR MAKING DECISIONS. THE STATEMENTS PROVIDING FACILITIES FOR PERFORMING REPETITIVE ACTIONS OR TAKING DECISIONS ARE CALLED PROGRAM CONTROL STATEMENTS.CONDITIONAL STATEMENTS
THE CONDITIONAL STATEMENTS ALLOW TO CHOOSE THE SET OF INSTRUCTIONS FOR EXECUTION DEPENDING UPON AN EXPRESSION'S TRUTH VALUE.THE IF STATEMENT
A SIMPLE IF STATEMENT TESTS A PARTICULAR CONDITION AND IF THE CONDITION EVALUATES TO TRUE A SET OF STATEMENT IS EXECUTED.SYNTAX :
IF ( EXPRESSION )
{
STATEMENT 1;
}
EXAMPLE :
IF ( NUM < 0 )
NUM = -NUM;
IF ELSE STATEMENT
WHEN A SERIES OF DECISION ARE INVOLVED, WE USE IF ELSE STATEMENT.SYNTAX :
IF ( EXPRESSION )
{
STATEMENT 1;
}
ELSE
{
STATEMENT 2;
}
IF THE TEST EXPRESSION EVALUATES TO TRUE VALUE, THE STATEMENT 1 IS EXECUTED, OTHERWISE STATEMENT 2 IS EXECUTED.
EXAMPLE :
CPP PROGRAM TO CHECK WHETHER A GIVEN NUMBER IS ODD OR EVEN.
# INCLUDE < IOSTREAM.H >
# INCLUDE < CONIO.H >
VOID MAIN ( )
{
INT N;
CLRSCR ( );
COUT<<" ENTER THE NUMBER : ";
CIN>>N;
IF ( N % 2 == 0 )
COUT<<N<<" IS EVEN NUMBER";
ELSE
COUT<<N<<" IS ODD NUMBER";
GETCH ( );
}
IF ELSE IF LADDER
A COMMON PROGRAMMING CONSTRUCT IN C++ IS THE IF ELSE IF LADDER, WHICH IS ALSO KNOWN AS IF ELSE IF STAIR CASE BECAUSE OF ITS APPEARANCE.
SYNTAX :
IF ( EXPRESSION )
STATEMENT 1;
ELSE IF ( EXPRESSION )
STATEMENT 2;
ELSE IF ( EXPRESSION )
STATEMENT 3;
ELSE
STATEMENT 4;
EXAMPLE :
CPP PROGRAM TO CHECK WHETHER A GIVEN CHARACTER IS UPPERCASE OR LOWERCASE.
# INCLUDE < IOSTREAM .H >
# INCLUDE < CONIO.H >
VOID MAIN ( )
{
CHAR CH;
CLRSCR ( );
IF ( CH >= 'A' && CH <= 'Z' )
COUT<<" UPPER CASE CHARACTERS ";
ELSE IF ( CH >= 'a' && CH <= 'z' )
COUT<<" LOWER CASE CHARACTERS ";
ELSE IF ( CH >= '1' && CH <= '9' )
COUT<<" IT IS A DIGIT ";
ELSE
COUT<<" IT IS A SPECIAL CHARACTER ";
GETCH ( );
}
NESTED IF
A NESTED IF IS AN IF STATEMENT THAT HAS ANOTHER IF IN ITS IFS BODY OR ELSE'S BODY.SYNTAX :
IF ( EXPRESSION 1 )
{
IF ( EXPRESSION 2 )
STATEMENT 1;
ELSE
STATEMENT 2;
}
ELSE
BODY OF IF
EXAMPLE :
CPP PROGRAM TO FIND BIGGEST AMONG THREE NUMBERS
# INCLUDE < IOSTREAM.H >
# INCLUDE < CONIO.H >
VOID MAIN( )
{
INT A,B,C,BIG;
CLRSCR( );
COUT<<" ENTER THREE NUMBER ";
CIN>>A>>B>>C;
IF ( A > B )
{
IF ( A > C )
BIG = A;
ELSE
BIG = C;
}
ELSE
{
IF ( B > C )
BIG = B;
ELSE
BIG = C;
}
COUT<<" BIGGEST NUMBER IS "<<BIG<<END1;
GETCH( );
}
THE SWITCH STATEMENT
C++ PROVIDES A MULTIPLE BRANCH SELECTION STATEMENT KNOWN AS SWITCH. THIS SELECTION STATEMENT SUCCESSIVELY LESS THE VALUE OF AN EXPRESSION AGAINST A LIST OF INTEGER OR CHARACTER CONSTANTS.SYNTAX :
SWITCH ( EXPRESSION )
{
CASE 1 : STATEMENT 1; BREAK;
CASE 2 : STATEMENT 2; BREAK;
CASE 3 : STATEMENT 3; BREAK;
CASE N - 1 : STATEMENT N - 1; BREAK;
}
THE EXPRESSION IS EVALUATED AND ITS VALUES ARE MATCHED AGAINST THE VALUES OF THE CONSTANTS IN THE CASE STATEMENTS. WHEN A MATCH IS FOUND, THE STATEMENT SEQUENCE ASSOCIATED WITH THAT CASE IS EXECUTED UNTIL THE END OF THE SWITCH STATEMENT IS REACHED.
EXAMPLE :
CPP PROGRAM TO PRINT THE NAME OF THE DAY OF THE WEEK
# INCLUDE < IOSTREAM.H >
# INCLUDE < CONIO.H>
VOID MAIN ( )
{
INT DW;
CLRSCR ( );
COUT<<" ENTER NUMBER OF WEEK'S DAY 1 - 7 : ";
CIN>>DW;
SWITCH ( DW )
{
CASE 1 : COUT<<"\N SUNDAY "; BREAK;
CASE 2 : COUT<<"\N MONDAY "; BREAK;
CASE 3 : COUT<<"\N TUESDAY "; BREAK;
CASE 4 : COUT<<"\N WEDNESDAY"; BREAK;
CASE 5 : COUT<<"\N THURSDAY "; BREAK;
CASE 6 : COUT<<"\N FRIDAY "; BREAK;
CASE 7 : COUT<<"\N SATURDAY "; BREAK;
DEFAULT : COUT<<"\N INVALID DAY NUMBER ";
}
GETCH ( );
}
NESTED SWITCH
NESTED SWITCH STATEMENT MEANS THE SWITCH STATEMENT WITH ANOTHER SWITCH STATEMENT IS CALLED AS NESTED SWITCH STATEMENT.EXAMPLE :
SWITCH ( A )
{
CASE 1 : SWITCH ( B )
{
CASE 0 : COUT<<" DIVIDE BY ZERO ERROR ";
CASE 1 : RES = A / B;
}
BREAK;
}
FOR LOOP
FOR LOOP IS AN ENTRY CONTROLLED LOOPING STATEMENT. A LOOP IS USED FOR EXECUTING A BLOCK OF STATEMENT REPEATEDLY UNTIL A PARTICULAR CONDITION IS TRUE.SYNTAX :
FOR ( INITIALIZATION EXPRESSION; TEST EXPRESSION; UPDATE EXPRESSION );
BODY OF THE LOOP;
IN AN ENTRY CONTROLLED LOOP, THE TEST EXPRESSION IS EVALUATED BEFORE ENTERING INTO A LOOP.
- FIRSTLY INITIALIZATION EXPRESSION IS EVALUATED.
- THEN, THE TEST EXPRESSION IS EVALUATED.
- IF THE TEST EXPRESSION IS TRUE, THE BODY OF THE LOOP IS EXECUTED.
- AFTER EXECUTING THE LOOP BODY, THE UPDATE EXPRESSION IS EXECUTED.
- AGAIN THE TEST EXPRESSION IS EVALUATED. IF IT IS TRUE THE SEQUENCE REPEATES, OTHERWISE THE LOOP TERMINATES.
EXAMPLE :
CPP PROGRAM TO PRINT THE MULTIPLICATION OF A GIVEN NUMBER
# INCLUDE < IOSTREAM.H >
# INCLUDE < CONIO.H >
VOID MAIN ( )
{
INT N, I;
CLRSCR ( );
COUT<<" ENTER THE NUMBER : ";
CIN>>N;
FOR ( I = 1; I < 12; I++ )
COUT<<I<<" " <<N<<" = "<< I * N<<END1;
GETCH ( );
}
WHILE LOOP
THE WHILE LOOP IS AN ENTRY CONTROLLED LOOPING STATEMENT.SYNTAX :
WHILE ( EXPRESSION )
BODY OF THE LOOP;
THE LOOP ITERATES WHILE THE EXPRESSION EVALUATES TO TRUE. WHEN THE EXPRESSION BECOMES FALSE, THE PROGRAM CONTROL PASSES TO THE LINE AFTER THE LOOP BODY. IN THE WHILE LOOP THE LOOP CONTROL VARIABLE SHOULD INITIALIZED BEFORE THE LOOP BEGINS.
DO WHILE LOOP
THE DO WHILE LOOP IS AN EXIT CONTROLLED LOOPING STATEMENT. IN AN EXIT CONTROLLED LOOP, THE TEST EXPRESSION IS EVALUATED BEFORE EXITING FROM THE LOOP. DO WHILE LOOP ALWAYS EXECUTES AT LEAST ONCE.SYNTAX :
DO
{
STATEMENTS;
}
WHILE ( TEST EXPRESSION );
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