Switch case and looping

What is computer program?
is a sequence of instruction written to perform a
specified task with a computer. A computer requires
programs to function, typically executing the
program's instructions in central processor. The
program has an executable form that the computer can
use directly to execute the instructions. The same
program in its human-readable source code
form, from which executable programs are derived
(e.g., compiled), enables a programmer to study and
develop its algorithms.

http://eglobiotraining.com/

 Computer source code is often written
by computer programmers. Source code is
written in a programming language that
usually follows one of two
main paradigms: imperative
programming or declarative programming.
Source code may be converted into
an executable file (sometimes called an
executable program or a binary) by
a compiler and later executed by a central
processing unit.

Computer Programmer
 is a person who writes computer software. The
term computer programmer can refer to a specialist in
one area of computer programming or to a generalist
who writes code for many kinds of software. One who
practices or professes a formal approach to
programming may also be known as a programmer
analyst.


 Programmers are people who design the
program of events that turns input data into
output data. It has been proved that such a
program of events can be designed using a
structure composed of sequences, iterations
and selections. Code is merely the way that
the program is described.


Programming is the iterative process of
writing or editing source code. Editing source
code involves testing, analyzing, and refining, and
sometimes coordinating with other programmers
on a jointly developed program. A person who
practices this skill is referred to as a
computer programmer, software developer or
coder. The sometimes lengthy process of
computer programming is usually referred to
as software development. The term software
engineering is becoming popular as the process is
seen as an engineering discipline.


Programming is instructing a computer to do
something for you with the help of a programming language.
The role of a programming language can be described in two
ways:
 Technical: It is a means for instructing a Computer to
perform Tasks
 Conceptual: It is a framework within which we organize our
ideas about things and processes.


 A Programming Language is
an artificial language designed to
communicate instructions to
a machine, particularly a computer.
Programming languages can be used to
create programs that control the behavior of
a machine and/or to
express algorithms precisely.


 Programming language is usually split into the two
components of syntax (form)
and semantics(meaning). Some languages are
defined by a specification document (for
example, the C programming language is specified
by an ISO Standard), while other languages, such
as Perl 5 and earlier, have a
dominant implementation that is used as
a reference.


 A programming language is a computer language
programmers use to develop applications, scripts, or
other set of instructions for a computer to execute.
Below is a listing of several different programming
languages and scripting languages currently listed in
our database.

ALGOL FORTRAN Prolog
Ada FoxPro Ruby
AIML HDML SGML
Assembly HTML Smalltalk
BASIC Java SQL
Batchfile JavaScript Tcl
BCPL JCL True BASIC
C LISP VHDL
C# Live Script Visual Basic
C++ LOGO Visual FoxPro
COBOL Pascal WML
CPL Perl WHTML
D PHP XML
DarkBASIC Pick
dBASE


The most important aspect of programming is to analyze
and adopt specific solution while solving any problem.
This needs a programming approach that defines the
modularity of program that one writes and how it is
related to others in an application.


C++ is a statically typed, free-form, multi-
paradigm, compiled, general-purpose programming
language. It is regarded as an intermediate-level
language, as it comprises a combination of both high-level
and low-level language features.

 C++ is one of the most popular programming languages
and is implemented on a wide variety of hardware and
operating system platforms.

C++ has greatly influenced many other popular
programming languages, most notably C# and Java. Other
successful languages such as Objective-C use a very
different syntax and approach to adding classes to C.


 C++ is one of the most used programming languages
in the world. Also known as "C with Classes".
 C++ is a general-purpose programming language with
high-level and low-level capabilities. It is a statically
typed, free-form, multi-paradigm, usually compiled
language supporting procedural programming, data
abstraction, object-oriented programming, and
generic programming.


Switch Case
 In programming, a switch, case, select or inspect sta
tement is a type of selection control mechanism that
exists in most imperative programming languages
such as Pascal, Ada, C/C++, C#, Java, and so on.
 The main reasons for using a switch 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.


 The switch-case statement is a multi-way
decision statement. Unlike the multiple
decision statement that can be created
using if-else, the switch statement
evaluates the conditional expression and
tests it against numerous constant values.


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;
}

Switch case statements are 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). The basic format for using switch case is outlined
below. 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 executing the program from that point.


 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 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.


int a = 10;
int b = 10;
Sadly, it isn't legal to use case
int c = 20;
like this:
switch ( a ) {
case b:
/* Code */
break;
case c:
/* Code */
break;
default:
/* Code */
break;
}

 The default case is optional, but it is wise to
include it as it handles any unexpected cases. 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 are met. Often it can be used to
process input from a user.


#include <iostream>

using namespace std;

void playgame()
{
cout << "Play game called";
}
void loadgame()
This is a sample
}
cout << "Load game called"; program, in which not
void playmultiplayer()
{
cout << "Play multiplayer game called";
all of the proper
}
functions are actually
int main()
{
int input;
declared, but which
cout<<"1. Play gamen";
cout<<"2. Load gamen";
shows how one would
cout<<"3. Play multiplayern";
cout<<"4. Exitn"; use switch in a program.
cout<<"Selection: "; cin>> input;
switch ( input ) {
case 1: // Note the colon, not a semicolon
playgame();
break;
loadgame();
break;
playmultiplayer();
break;
cout<<"Thank you for playing!n";
break;
default: // Note the colon, not a semicolon
cout<<"Error, bad input, quittingn";
break;
}
cin.get();
}

 This program will compile, but cannot be run until the
undefined functions are given bodies, but it serves as a
model (albeit simple) for processing input. If you do
not understand this then try mentally putting in if
statements for the case statements. Default simply
skips out of the switch case construction and allows
the program to terminate naturally. If you do not like
that, then you can make a loop around the whole thing
to have it wait for valid input. You could easily make a
few small functions if you wish to test the code.


Looping
In computer programming, a loop is a sequence
of instructions that is continually repeated until a
certain condition is reached. Typically, a certain
process 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 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 the loop. A loop is a
fundamental programming idea that is commonly
used in writing programs.


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 -- many programs or websites that
produce extremely complex output (such as a message
board) are really only executing a single task many
times. (They may be executing a small number of
tasks, but in principle, to produce a list of messages
only requires repeating the operation of reading in
some data and displaying it.) Now, think about what
this means: a loop lets you write a very simple
statement to produce a significantly greater result
simply by repetition.


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
 do..while


For
A for loop allows a
statement to be
executed a specified
number of times.


pseudo code  The for loop begins with a
loop control variable
for (initial-value, final-value, increment) assigned a specific initial
statement-1 value. This control variable
in then incremented (or
decremented) by a
specified amount each
Example:
time around the loop until
a specified terminating
for (a = 3, a > 12, a = a + 2)
value is reached at which
print a
time the statement
following the loop is then
This example will output 3 5 7 9 11.
executed


While
A while loop allows a
statement to be executed
until a given condition is
met. If the condition is
met prior to executing
the loop then the loop
will not be executed. As
soon as the condition is
met, execution continues
with the statement
following the loop.


Pseudo code

while not condition
statement-1
WHILE loops are very simple.

Example:

#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();
}

DO..WHILE
DO..WHILE loops are useful for things that want to loop at
least once.

In most computer programming languages, a do while
loop, sometimes just called a do loop, is a control flow
statement that allows code to be executed repeatedly
based on a given Boolean condition. Note though that
unlike most languages, Fortran's do loop is actually
analogous to the for loop.


Pseudo code do {
} while ( condition );

 Example:
Notice that the condition is
#include <iostream> tested at the end of the
block instead of the
using namespace std; beginning, so the block will
be executed at least once. If
int main() the condition is true, we
Example: jump back to the beginning
{
int x; of the block and execute it
again. A do..while loop is
x = 0; basically a reversed while
do { loop. A while loop says
// "Hello, world!" is printed at least one time "Loop while the condition
// even though the condition is false is true, and execute this
cout<<"Hello, world!n"; block of code", a do..while
} while ( x != 0 ); loop says "Execute this
cin.get(); block of code, and loop
} while the condition is
true".

Codes and Explanations of the Program
have been tested


Switch Case


#include<stdio.h>
#include<conio.h>
main()
{
int choice;
float x,y;
Switch case 1
printf("Enter the value of 1st:");
scanf("%f",&x);
printf("Enter the value of 2nd :");
scanf("%f",&y);

printf("1.Addn");
printf("2.Subtactn");
printf("3.Multificationn");
printf("4.Divisionn");
printf("nnnEnter your choice[1-4]: ");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("THE result is :%f",x+y);
break;
case 2:
printf("The result is :%f",x-y);
break;
case 3:
printf("The result is :%f",x*y);
break;
case 4:
printf("The result is :%f",x/y);
break;
default:
printf("unknown");
}
fflush(stdin);
getchar();
}

#include <iostream>


int main(){
cout << "Enter a number between 1 and 5!" << endl; Switch case 2
int number;
cin >> number;
switch(number){
case 1: //if (number == 1)
cout << "one";
break;
case 2: //else if(number == 2) and so on...
cout << "two";
break;
case 3:
cout << "three";
break;
case 4:
cout << "four";
break;
case 5:
cout << "five";
break;
default: //if number is NOT 1,2,3,4 or 5
cout << number << " is not between 1 and 5!";
}
cout << endl;
system("pause");
}

#include <iostream>
int main(void)
{
char grade;
cout << "Enter your grade: ";
 Switch case 3
cin >> grade;
switch (grade)
{
case 'A':
cout << "Your average must be between 90 - 100"
<< endl;
break;
case 'B':
<< endl;
break;
case 'C':
<< endl;
break;
case 'D':
<< endl;
break;
default:
cout << "Your average must be below 60" << endl;
}
return 0;
}

#include <stdlib.h>
#include <stdio.h>

int main(void) {
int n;
printf("Please enter a number: ");  Switch case 4
scanf("%d", &n);
switch (n) {
case 1: {
printf("n is equal to 1!n");
break;
}
case 2: {
break;
}
case 3: {
break;
}
default: {
printf("n isn't equal to 1, 2, or 3.n");
break;
}
}
system("PAUSE");
return 0;
}


#include <iostream.h>
int main(void)  Switch case 5
{
int day;
cout << "Enter the day of the week between 1-7::";
cin >> day;
switch(day)
{
case 1:
cout << "Monday";
break;
case 2:
cout << "Tuesday";
break;
case 3:
cout << "Wednesday";
break;
case 4:
cout << "Thursday";
break;
case 5:
cout << "Friday";
break;
case 6:
cout << "Saturday";
break;
default:
cout << "Sunday";
break;
}
}


Looping


#include <iostream> Looping 1
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();
}


#include <iostream>
#include <stdlib.h>
int main()
{
int x, score, tnum_stud, t_score, ave_score;
char student_name[20];
tnum_stud = 0, t_score = 0, ave_score = 0;
cout<< "Enter student name: ";
Looping 2
cin>>student_name;
cout<< "Enter score: ";
cin>> score;
t_score = t_score + score;
for (x = 1; x <= 4; x++)
{
cout<< "Enter score: ";
cin>> score;
t_score = t_score + score;
}
tnum_stud = x++;
ave_score = t_score/tnum_stud;
cout<< "Total no. of students: "
<<tnum_stud<<endl;
cout<< "Total score: " <<t_score<<endl;
cout<< "Total average score: "
<<ave_score<<endl;
tnum_stud = 0, t_score = 0, ave_score = 0;
cout<< "nnn";
system ("PAUSE");
return 0;
}


Looping 3
int main()
{
int x = 0;
do
{
cout<<"This will loop 2 times
and stop."<<endl;
}while(x != 1);
return 0;
}


// custom countdown using while

#include <iostream>

int main ()
{
Looping 4
int n;
cout << "Enter the starting number
> ";
cin >> n;

while (n>0) {
cout << n << ", ";
--n;
}

cout << "FIRE!n";
return 0;
}



int main()
{
int x;
while (x != 0)
Looping 5
{
cout<<"What would you
like to do? (0 - Quit 1 - Stay):
"<<endl;
cin>>x;
}
return 0;
}


An output
program using Dev C++


Switch case 1

 Take a look at the placement of the curly
brackets and how the indentations are placed.
This is all done to make reading easier and to
make less mistakes in large programs.


Switch case 2

If you use an “if statement” in an “if statement” it is called
nesting. Nesting ”if statements” can make a program
very complex, but sometimes there is no other way. So
use it wisely.

Switch case 3

The if statement can be used to test
conditions so that we can alter the flow of
a program. In other words: if a specific
statement is true, execute some
instructions. If not true, execute these
instructions.

The program's end functionality has not changed, only
the method of implementation in the C++ source
code. The program reads user input from the
keyboard until the return key is pressed. After the user
inputs a number, that value is stored into the integer
variable "n". The variable "n" is then tested by a switch
statement. If the user inputs the number 1, then "n is
equal to 1!" is printed as shown below.

Switch case 4

In the above Control Structure example the
"switch" statement is used to find the day of
the week from the integer input got from the
user.

http://eglobiotraining.com/ Switch case 5

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 is incremented
after the code in the loop is run for the first time.
http://eglobiotraining.com/ Looping 1

If the “default” block is last block in your switch order,
then it isn’t necessary to state break next to it.
Consequence of falling through case labels in lack of
break order is that the same collection of orders is
executed for more different case labels.


Keep in mind that you must include a trailing semi-colon after the
while in the above example. A common error 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.

Looping 3

When the program starts the user is prompted to
insert a starting number for the countdown. Then
the while loop begins, if the value entered by the
user fulfills the condition n>0 (that n is greater
than zero) the block that follows the condition will
be executed and repeated while the condition
(n>0) remains being true.


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.

Looping 5

Submitted to:
Prof. Erwin Globio

Submitted by:
Hidalgo, Patricia M.
BM10203

http://eglobiotraining.com/ 56

Switch case and looping

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