Fundamentals of programming)

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Fundamentals of Programming


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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 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. Sadly, it isn't legal to use case like this.







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.







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.




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. The branch corresponding to the value that

the expression matches is taken during execution.

The value of the expressions in a switch-case statement must

be an ordinal type i.e. integer, char, short, long etc. Float and

double are not allowed.

The syntax is :




The case statements and

the default statement can occur in any

order in the switch statement.

The default clause is an optional clause

that is matched if none of the constants

in the case statements can be matched.

Consider the example shown below:




Here, if the Grade is 'A' then the output will

be:




This is because, in the 'C' switch statement,

execution continues on into the next case clause if it is not explicitly specified that the execution should exit the switch statement.

The correct statement would be:




Although the break in

the default clause (or in general,

after the last clause) is not

necessary, it is good

programming practice to put it in

anyway.

An example where it is better to

allow the execution to continue

into the next case statement:











Looping Statements

while ( expression ) statement In a while loop, the expression is evaluated. If nonzero, the statement executes, and the expression is evaluated again. This happens over and over until the expression's value is zero. If the expression is zero the first time it is evaluated, statement is not executed at all.do statement while ( expression); A do while loop is just like a plain while loop, except the statement executes before the expression is evaluated. Thus, the statement will always be evaluated at least once.

for ( expression1; expression2; expression3 ) statement In a for loop, first expression1 is evaluated. Then expression2 is evaluated, and if it is zero EEL leaves the loop and begins executing instructions after statement. Otherwise the statement is executed, expression3 is evaluated, and expression2 is evaluated again, continuing until expression2 is zero.

You can omit any of the expressions. If you omit expression2, it is like expression2 is nonzero. while (expression) is the same as for (; expression; ). The syntax for (;;) creates an endless loop that must be exited using the break statement (or one of the other statements described below).




The for loop construct is used is used to

repeat a statement or block of

statements a specific number of times.

The while loop construct only contains

condition.

The do while, the difference between do

while loop and other loops is that in the

do while loop the condition comes after

the statement




The break keyword is used to terminate a

loop, intermediately bypassing any

conditions. The control will be transferred

to the first statement following the loop

block. The break statement can be used

to terminate an infinite loop or to force a

loop to end before its normal

termination.







#include<stdio.h>

#include<conio.h>

int main(void)

{

int n;

printf("input year level: ");

scanf("%d",&n);

switch(n)

{

case 1:

printf("freshmen");

break;

case 2:

printf("sophomores");

break;

case 3:

printf("juniors");

break;

case 4:

printf("seniors");

break;

default:

printf("invalid");

break;

}

getch();

return 0;

}


Output



If the user will input a number until 1 – 4

the program will answer, but if the user

input higher number it will be invalid.

Example:

If the user will input “1” the variable n will

have its value 1 and the variable will be

used in the switch statement and it will

provide its equivalent value in case. The

answer will be “freshmen”.




fil#include<stdio.h>

#include<conio.h>

int main(void)

{

int n1,n2,r;

char o;

printf("select an operation \na)addition \nb)subtraction \nc)multiplication \nd)division ");

scanf("%c",&o);

switch(o)

{

case 'a':

printf("input 1st number:");

scanf("%d",&n1);

printf("input 2nd number:");

scanf("%d",&n2);

r=n1+n2;

printf("%d",r);

break;

case 'b':


scanf("%d",&n1);


scanf("%d",&n2);

r=n1-n2;

printf("%d",r);

break;

case 'c':


scanf("%d",&n1);


scanf("%d",&n2);

r=n1*n2;

printf("%d",r);

break;

case 'd':


scanf("%d",&n1);


scanf("%d",&n2);

r=n1/n2;

printf("%d",r);

break;

default:

printf("invalid");

break;

}

getch();

return 0;

} http://eglobiotraining.com.

Output



The user will choose one operation if the

user choose “d” then it will have the

value for case d that is division. Then the

program will ask you to provide the first

number and second number, then if you

have already given the two values it will

quickly give you the answer.




#include<stdio.h>

#include<conio.h>

int main(void)

{

int n,x;

printf("input a number: ");

scanf("%d",&n);

if(n>=0)

{

x=1;

}

else

{

x=2;

}

switch(x)

{

case 1:printf("positive");break;

case 2:printf("negative");break;

default:printf("invalid");break;

}

getch();

return 0;

}


Output



Input a number, then the value of n will

be the input number. There is a condition

statement that if n is greater than or

equal to 0 x will be equal to one, the

value of x will switch and become the

value of case.




#include<stdio.h>

#include<conio.h>

int main(void)

{

int n1,n2,x;

printf("input 1st number: ");

scanf("%d",&n1);

printf("input 2nd number: ");

scanf("%d",&n2);

if(n1>n2)

{

x=1;

}

else if(n2>n1)

{

x=2;

}

else

{

x=3;

}

switch(x)

{

case 1:printf("Higher: %d Lower: %d",n1,n2);;break;

case 2:printf("Higher: %d Lower: %d",n2,n1);;break;

default:printf("equal");break;

}

getch();

return 0;

}


Output



The user must input two numbers. The first

number will serve as the n1 and the

second number is the n2. If you already

put the two numbers the values will

switch and the program will determine

the higher and the lower value.




#include<stdio.h>

#include<conio.h> int main(void) { int n,x,y;

printf("input a number: "); scanf("%d",&n); x=n%2; if(x==0)

{ y=1; } else

{ y=2; }

switch(y) { case 1:printf("even");break;

case 2:printf("odd");break; default:printf("invalid");break; }

getch(); return 0; }


Outpu

t



The user must input number and that

number that has been encoded will be

divided into two, then the answer that

will come out will be the value of x. And

lastly the program will determine if it is an

odd, even or invalid.




#include<stdio.h>

#include<conio.h>

int main(void)

{

int ctr;

for(ctr=1;ctr<=5;ctr++)

{

printf("%d",ctr);

}

getch();

return 0;

}


Output



The variable ctr is equal to one, if ctr is

less than or equal to 5, if it is true it will

print value of ctr that is 1 then to the next

ctr value the first value will be added so

it will become 2 and so on and so forth.




#include<stdio.h>

#include<conio.h>

int main(void)

{

int ctr;

for(ctr=10;ctr>=1;ctr--)

{

printf(" %d",ctr);

}

getch();

return 0;

}


Output



The value of ctr is equal to 10 if the ctr is

greater that or equal to 1 and if it is true

the value 10 will be deducted by 1 and

so on and so forth.




#include<stdio.h>

#include<conio.h>

int main(void)

{

int ctr=2;

while(ctr<=20)

{

printf(" %d",ctr);

ctr=ctr+2;

}

getch();

return 0;

}


Output



The value of ctr is 2 if the ctr is less than or

equal to 20 then the value of ctr that is 2

will become 4 because the program will

add another 2 and again and again

and again.




#include<stdio.h>

#include<conio.h>

int main(void)

{

int x=1,y=5;

while(x<=5)

{

printf(" %d %d",x,y);

x++;

y--;

}

getch();

return 0;

}


Output



The value of x is 1 and y is equal to 5. If

the x is less than or equal 5 then the

value of 1 will be added by 1 and the

value of y will be subtracted by 1.




#include<stdio.h>

#include<conio.h>

int main(void)

{

int ctr;

ctr=1;

do

{

printf(" jake %d",ctr);

ctr++;

}while(ctr<=10);

getch();

return 0;

}

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Output


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The value of ctr is 1 if the value of ctr is less than or equal to 10 then the value will be added by 1 and so on and so forth.

This file is to be submitted by:

Prof. Erwin M. Globio





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Fundamentals of programming)