3. Switch Case Statement
In programming,
a switch, case, select or inspect statement is a
type of selection control mechanism that exists in
most imperative programming languages such
as Pascal, C/C++, C#, Java, and so on.
It is also included in several other types of
languages.
Its purpose is to allow the value of a variable or
expression to control the flow of program
execution via a multiway branch (or "goto", one of
several labels).
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4. Switch Case
The main reasons for using a switch in programming
include improving clarity, by reducing otherwise
repetitive coding, and (if the heuristics permit) also
offering the potential for faster execution through
easier compiler optimization in many cases.
It is a substitute for long if statements that compare a
variable to several "integral" values ("integral" values
are simply values that can be expressed as an
integer, such as the value of a char).
In computer programming, the value of the variable
given into switch is compared to the value following
each of the cases, and when one value matches the
value of the variable, the computer continues
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executing the program from that point.
5. The basic format for using switch
case is outlined below.
switch ( <variable> )
{
case this-value:
Code to execute if <variable> == this-value
break;
case that-value:
Code to execute if <variable> == that-value
break;
...
default:
Code to execute if <variable> does not equal the value following any of
the cases
break;
}
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6. Switch Case
In computer programming, the condition of a switch
statement is a value. The case says that if it has the value
of whatever is after that case then do whatever follows the
colon. The break is used to break out of the case
statements. Break as one of the language used in
programming is a keyword that breaks out of the code
block, usually surrounded by braces, which it is in.
In this case, break prevents the program from falling
through and executing the code in all the other case
statements. An important thing to note about the switch
statement is that the case values may only be constant
integral expressions.
It can be useful to put some kind of output to alert you to
the code entering the default case if you don't expect it to.
Switch statements serve as a simple way to write long if
statements when the requirements of programming are
met. Often it can be used to process input from a user.
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7. Actual Source code of switch
case
#include <iostream> switch ( input ) {
case 1: // Note the colon, not a semicolon
using namespace std; playgame();
break;
void playgame() case 2: // Note the colon, not a semicolon
{ loadgame();
cout << "Play game called"; break;
} case 3: // Note the colon, not a semicolon
void loadgame() playmultiplayer();
{ break;
cout << "Load game called"; case 4: // Note the colon, not a semicolon
} cout<<"Thank you for playing!n";
void playmultiplayer() break;
{ default: // Note the colon, not a semicolon
cout << "Play multiplayer game called"; cout<<"Error, bad input, quittingn";
} break;
int main() }
{ cin.get();
int input; }
cout<<"1. Play gamen";
cout<<"2. Load gamen";
cout<<"3. Play multiplayern";
cout<<"4. Exitn";
cout<<"Selection: ";
cin>> input;
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9. Explanation
In this program, the user will select if he wants to
play, load, play multiplayer or close the game
based on the number indicated in the output
program of the programming software.
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10. Actual Source code of Program 2
#include <stdlib.h> case 3:
#include <stdio.h> {
printf("n is equal to 3!n");
int main(void) { break;
int n; }
printf("Please enter a number: "); default:
scanf("%d", &n); {
switch (n) printf("n isn't equal to 1, 2, or 3.n");
{ break;
case 1: }
{ }
printf("n is equal to 1!n"); system("PAUSE");
break; return 0;
} }
case 2:
{
printf("n is equal to 2!n");
break;
}
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12. Explanation
#include <iostream>
- This tells the compiler to include files in using dev
c++ of programming.
#include <stdlib.h>
- This tells the compiler to include files.
int main(int argc, char *argv[])
- This starts the main function use in programming.
This 2nd example program that I did for the
requirement in programming will ask the user to select
a number. After entering the number, the
programming software which is the dev c++ program
will print if the entered number is equal to 1, 2 or 3. It
will print different things on the screen depending on
which number the user chose.
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13. Actual source code of program 3
#include <iostream.h>
int main()
{
unsigned short int number;
cout << "Enter a number between 1 and 5: ";
cin >> number;
switch (number)
{
case 0: cout << "Too small, sorry!";
break;
case 5: cout << "Good job!n"; // fall through
case 4: cout << "Nice Pick!n"; // fall through
case 3: cout << "Excellent!n"; // fall through
case 2: cout << "Masterful!n"; // fall through
case 1: cout << "Incredible!n";
break;
default: cout << "Too large!n";
break;
}
cout << "nn";
return 0;
}
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15. explanation
This 3rd program of programming will ask the
user to select a number between 1 and 5. Then
the program will print different things on the
screen depending on which number the user
chose. The switch statement can be very helpful
in handling multiple choices in programming.
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16. Actual source code of program 4
#include <iostream> void welcome()
#include <stdlib.h> {
cout << "This program displays different messages
dependingn";
using namespace std;
cout << "on which number is entered by the user.n";
void welcome();
cout << "Pick a number between 1 and 6 to see whatn";
int getInteger();
cout << "the program will say.nn";
void displayResponse(int choice);
} // end of welcome function
int main(int argc, char *argv[])
// getInteger asks the user for a number between 1 and 6.
{
// The integer is returned to where the function was called.
int choice; // declares the choice variable
int getInteger()
welcome(); // This calls the welcome function
{
choice = getInteger(); // calls getInteger and receives the
value for choice int response; // declares variable called response
displayResponse(choice); // passes choice to cout << "Please type a number between 1 and 6: "; // prompt
displayResponse function for number
cin >> response; // gets input from user and assigns it to
response
system("PAUSE");
return response; // sends back the response value
return 0;
} // end getInteger function
} // end main
// displayResponse function takes the int variable and uses it
// welcome function displays an opening message to
// explain the program to the user
// to determine which set of tasks will be performed.
void displayResponse(int choice)
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17. Source code
{ case 5: // choice was the number 5
int again; cout << "Counting by fives is fun. Five, Ten,
Fifteen, Twenty...nn";
break; // this ends the statements for case 5
// switch statement based on the choice variable
switch (choice) // notice no semicolon case 6: // choice was the number 6
cout << "Six is divisible by two and three.nn";
{
break; // this ends the statements for case 6
case 1: // choice was the number 1
default: // used when choice falls out of the
cout << "One is a lonely number and very useful cases covered above
in math.nn";
cout << "You didn't pick a number between 1
break; // this ends the statements for case 1 and 6.nn";
case 2: // choice was the number 2 again = getInteger(); // gives the user another
cout << "Two is the only even prime try
number.nn"; displayResponse(again); // recalls
break; // this ends the statements for case 2 displayResponse with new number
case 3: // choice was the number 3 break;
cout << "Three is a crowd and also a prime } // end of switch statement
number.nn"; } // end displayResponse function
break; // this ends the statements for case 3
case 4: // choice was the number 4
cout << "Four square is a fun game to play, but
four squared is ";
cout << 4 * 4 << ".nn";
break; // this ends the statements for case 4
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19. explanation
This is the 4th example that I included in my final
requirement in programming. This program
displays different messages depending on which
number is entered by the user. The user will be
asked to pick a number between 1 and 6 to see
what the program will say. Then, after the user
enter the number, the programming software will
print if it is an even or odd number.
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20. Actual Source code of program 5
#include <iostream> void welcome()
#include <stdlib.h> {
cout << "This program displays different messages
dependingn";
using namespace std;
cout << "on which letter is entered by the user.n";
void welcome();
cout << "Pick a letter a, b or c to see whatn";
char getChar();
cout << "the program will say.nn";
void displayResponse(char choice);
} // end of welcome function
int main(int argc, char *argv[])
// getChar asks the user for a letter a, b or c.
{
// The character is returned to where the function was called.
char choice; // declares the choice variable
char getChar()
welcome(); // This calls the welcome function
{
choice = getChar(); // calls getChar and returns the value for
choice char response; // declares variable called response
displayResponse(choice); // passes choice to
displayResponse function
cout << "Please type a letter a, b or c: "; // prompt for letter
cin >> response; // gets input from user and assigns it to
system("PAUSE"); response
return 0; return response; // sends back the response value
} // end main } // end getChar function
// welcome function displays an opening message to // displayResponse function takes the char variable and uses it
// explain the program to the user // to determine which set of tasks will be performed.
void displayResponse(char choice)
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21. Source code
{
char again;
// switch statement based on the choice variable
switch (choice) // notice no semicolon
{
case 'A': // choice was the letter A
case 'a': // choice was the letter a
cout << "A is for apple.nn";
break; // this ends the statements for case A/a
case 'B': // choice was the letter b
case 'b': // choice was the letter b
cout << "B is for baseball.nn";
break; // this ends the statements for case B/b
case 'C': // choice was the letter C
case 'c': // choice was the letter c
cout << "C is for cat.nn";
break; // this ends the statements for case C/c
default: // used when choice falls out of the cases covered above
cout << "You didn't pick a letter a, b or c.nn";
again = getChar(); // gives the user another try
displayResponse(again); // recalls displayResponse with new character
break;
} // end of switch statement
} // end displayResponse function
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23. Explanation
The final program of the requirement in
programming project displays different messages
depending on which letter is entered by the user.
The user will be asked to pick a letter a, b or c to
see what the program will say. Then, after the
user enter the number, the programming software
which is the dev c++ will print if it is an even or
odd number.
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25. Looping statement
In computer programming, a loop is a sequence
of instructions that is continually repeated until a
certain condition is reached.
Typically, a certain process in programming is
done, such as getting an item of data and
changing it, and then some condition is checked
such as whether a counter has reached a
prescribed number.
If it hasn't, the next instruction used in
programming in the sequence is an instruction to
return to the first instruction in the sequence and
repeat the sequence. If the condition has been
reached, the next instruction "falls through" to the
next sequential instruction or branches outside
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26. A loop is a fundamental programming idea that
is commonly used in writing programs.
In object-oriented programming
language, whenever a block of statements has
to be repeated a certain number of times or
repeated until a condition becomes
satisfied, the concept of looping is used.
Loops are used to repeat a block of code.
Being able to have your program repeatedly
execute a block of code is one of the most
basic but useful tasks in programming.
One Caveat: before going further, you should
understand the concept of C++'s true and
false, because it will be necessary when
working with loops (the conditions are the same
as with if statements). There are three types of
loops: for, while, and do..while. Each of them
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27. The following commands used in C++ for
achieving looping:
for loop
while loop
do-while loop
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28. For loop
FOR - for loops are the most useful type in programming.
The syntax for a for loop is
for ( variable initialization; condition; variable update ) {
Code to execute while the condition is true
}
The variable initialization allows you to either declare a variable and give it a
value or give a value to an already existing variable. Second, the condition tells
the program that while the conditional expression is true the loop should continue
to repeat itself. The variable update section is the easiest way for a for loop to
handle changing of the variable. It is possible to do things like x++, x = x + 10, or
even x = random ( 5 ), and if you really wanted to, you could call other functions
that do nothing to the variable but still have a useful effect on the code.
Notice that a semicolon separates each of these sections, that is important. Also
note that every single one of the sections may be empty, though the semicolons
still have to be there. If the condition is empty, it is evaluated as true and the loop
will repeat until something else stops it. This is one of the important factors of a
programming language.
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29. Source code
#include <stdio.h>
int main()
{
int x;
/* The loop goes while x < 10, and x increases by one every loop*/
for ( x = 0; x < 10; x++ ) {
/* Keep in mind that the loop condition checks
the conditional statement before it loops again.
consequently, when x equals 10 the loop breaks.
x is updated before the condition is checked. */
printf( "%dn", x );
}
getchar();
}
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31. explanation
The variable initialization used in programming allows
you to either declare a variable and give it a value or
give a value to an already existing variable. Second,
the condition tells the program that while the
conditional expression is true the loop should
continue to repeat itself. The variable update section
is the easiest way for a for loop to handle changing of
the variable. It is possible to do things like x++, x = x +
10, or even x = random ( 5 ), and if you really wanted
to, you could call other functions that do nothing to the
variable but still have a useful effect on the code.
Notice that a semicolon separates each of these
sections, that is important. Also note that every single
one of the sections may be empty, though the
semicolons still have to be there. If the condition in
programming is empty, it is evaluated as true and the
loop will repeat until something else stops it.
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32. Source code
#include <iostream>
using namespace std; // So the program can see cout and endl
int main()
{
// The loop goes while x < 10, and x increases by one every loop
for ( int x = 0; x < 10; x++ ) {
// Keep in mind that the loop condition checks
// the conditional statement before it loops again.
// consequently, when x equals 10 the loop breaks.
// x is updated before the condition is checked.
cout<< x <<endl;
}
cin.get();
}
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34. explanation
This program is a very simple example of a for
loop. x is set to zero, while x is less than 10 it
calls cout<< x <<endl; and it adds 1 to x until the
condition is met. Keep in mind also that the
variable of a programming language is
incremented after the code in the loop is run for
the first time.
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35. While loop
WHILE - WHILE loops are very simple. The basic
structure is
while ( condition ) { Code to execute while the
condition is true } The true represents a boolean
expression which could be x == 1 or while ( x != 7 ) (x
does not equal 7). It can be any combination of
boolean statements that are legal. Even, (while x ==5
|| v == 7) which says execute the code while x equals
five or while v equals 7.
Notice that a while loop is the same as a for loop
without the initialization and update sections.
However, an empty condition is not legal for a while
loop as it is with a for loop.
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36. Source code
#include <iostream>
using namespace std; // So we can see cout and endl
int main()
{
int x = 0; // Don't forget to declare variables
while ( x < 10 ) { // While x is less than 10
cout<< x <<endl;
x++; // Update x so the condition can be met eventually
}
cin.get();
}
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38. explanation
This was another simple example, but it is longer
than the above FOR loop. The easiest way to
think of the loop is that when it reaches the brace
at the end it jumps back up to the beginning of
the loop, which checks the condition again and
decides whether to repeat the block another time,
or stop and move to the next statement after the
block.
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39. Do-while loop
DO..WHILE - DO..WHILE loops are useful for things in
programming that want to loop once. The structure is
do {
} while ( condition );
Notice that the condition is tested at the end of the block
instead of the beginning, so the block will be executed at
least once. If the condition is true, we jump back to the
beginning of the block and execute it again. A do..while
loop is basically a reversed while loop. A while loop says
"Loop while the condition is true, and execute this block of
code", a do..while loop says "Execute this block of
code, and loop while the condition is true".
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40. Source code
#include <iostream>
using namespace std;
int main()
{
int x;
x = 0;
do {
// "Hello, world!" is printed at least one time
// even though the condition is false
cout<<"Hello, world!n";
} while ( x != 0 );
cin.get();
}
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42. explanation
In this example, once you compile and run the
source codes you did, the programming software
will print “Hello, world!” even though the condition
is false.
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43. Source code
#include <iostream>
using namespace std;
int main()
{
int x;
x = 0;
do {
// "Hello, world!" is printed at least one time
// even though the condition is false
cout<<"Hello, world!n";
} while ( x != 0 );
cin.get();
}
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45. explanation
Keep in mind that you must include a trailing
semi-colon after the while in the above example.
A common error in programming is to forget that a
do..while loop must be terminated with a
semicolon (the other loops should not be
terminated with a semicolon, adding to the
confusion). Notice that this loop will execute
once, because it automatically executes before
checking the condition.
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