Switch case and looping

 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.

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 A programming language is a notation
for writing programs, which are
specifications of a computation
or algorithm.


 A computer programming language is a
language used to write computer
programs, which involve a computer
performing some kind of
computation or algorithm and possibly
control external devices such
as printers, disk drives, robots, and so on.


 Programming languages usually
contain abstractions for defining and
manipulating data structures or
controlling theflow of execution.


 As a student, I have learned that
programming is difficult to understand
because it has so many scripts and
applications that can be used to run a
program.


 First, I find programming very hard and
confusing because it has lots of codes
that you need to understand for you to
run a program.


 Programming is a creative process done
by programmers to instruct a computer
on how to do a task. Programming
languages let you use them in different
ways, e.g. adding numbers, etc… or
storing data on disk for later retrieval.


 You need to consider languages to run
your own program. DEV C++ is the most
language that we use in programming.
 C++ is one of the most used
programming languages in the world.
Also known as "C with Classes".


 In programming,
a switch, case, select or inspect statement i
s a type of selection control mechanism
that exists in most imperative
programminglanguages such
as Pascal, Ada, C/C++, C#, Java, and so
on
 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).

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;
}

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.


The default case is optional, but it is wise to include it as it handles any unexpected cases. Switch
statements serves 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.

Above is a sample program, in which not all of the proper functions are actually declared, but
which shows how one would use switch in a program.

 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.


 LOOP is a pedagogical programming
language designed by Uwe Schöning,
along with GOTO and WHILE. The only
operations supported in the language
are assignment, addition and looping.


 A loop lets you write a very simple
statement to produce a significantly
greater result simply by repetition.
 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).


 For
 While and
 Do


For ( variable initialization; condition; variable update ) {
Code to execute while the condition is true
}


 Here statement(s) may be a single
statement or a block of statements.
The condition may be any expression,
and true is any nonzero value. The loop
iterates while the condition is true.
 When the condition becomes false,
program control passes to the line
immediately following the loop.


 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.


 The do-while loop is similar to
the while loop, except that the test
condition occurs at the end of the loop.
 Having the test condition at the end,
guarantees that the body of the loop
always executes at least one time.


do
{
block of code;
}
while (test 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".

 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.

#include <iostream>

int main()
{
using namespace std;

// nSelection must be declared outside do/while loop
int nSelection;

do
{
cout << "Please make a selection: " << endl;
cout << "1) Addition" << endl;
cout << "2) Subtraction" << endl;
cout << "3) Multiplication" << endl;
cout << "4) Division" << endl;
cin >> nSelection;
} while (nSelection != 1 && nSelection != 2 &&
nSelection != 3 && nSelection != 4);

// do something with nSelection here
// such as a switch statement

return 0;
}

#include <iostream>
int main()
{
int nSelection;
double var1, var2;

do
{
cout << "Please make a selection: " << endl;
cout << "1) Addition" << endl;
cout << "2) Subtraction" << endl;
cout << "3) Multiplication" << endl;
cout << "4) Division" << endl;
cin >> nSelection;
}

while (nSelection != 1 && nSelection != 2 &&
nSelection != 3 && nSelection != 4);

if (nSelection == 1)
{
cout << "Please enter the first whole number ";
cin >> var1;
cout << "Please enter the second whole number ";
cin >> var2;
cout << "The result is " << (var1+var2) << endl;
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{
cin >> var1;
cin >> var2;
cout << "The result is " << (var1-var2) << endl;
}
{
cin >> var1;
cin >> var2;
cout << "The result is " << (var1*var2) << endl;
}
{
cin >> var1;
cin >> var2;
cout << "The result is " << (var1/var2) << endl;
}

return 0;
}


else if (nSelection == 2)
{
cin >> var1;
cin >> var2;
cout << "The result is " << (var1-var2) << endl;
}
{
cin >> var1;
cin >> var2;
cout << "The result is " << (var1*var2) << endl;
}
{
cin >> var1;
cin >> var2;
cout << "The result is " << (var1/var2) << endl;
}
else
{
return 0;
}
}
}


#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();
}


#include <iostream>


int main ()

{

int score;

cout << "What was your score?";

cin >> score;

if (score <= 30)

{
cout << "nOuch, less than 30...!";

}


else if (score <= 50)

{

cout << "nYou score aint great mate..";

}


{

cout << "nYour pretty good, well done man!";

}


{

cout << "nYou got to the top!!!";

}


else

{

cout << "nYou cant score higher than 100!!! Cheater!!!!";

}

cin.ignore();

cin.get();

return 0;

}


#include <iostream>


int main(){
cout << "Enter a number between 1 and 5!" << endl;
int number;
cin >> number;
if(number == 1){
cout << "one";
}
else if(number == 2){
cout << "two";
}
cout << "three";
}
cout << "four";
}
cout << "five";
}
else{
cout << number << " is not between 1 and 5!";
}
cout << endl;
system("pause");
}


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

int main(void) {
int n;
printf("Please enter a number: ");
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;
}


 Submitted to:
Professor Erwin Globio

 Submitted by:
Charlaine J. Astillas

BM 10203


Switch case and looping

Switch case and looping

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