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==Checking for a Range of Values==

<source lang="cpp">#include <stdio.h>
main()
{
int iResponse = 0;
printf("Enter a number from 1 to 10: ");
scanf("%d", &iResponse);
if ( iResponse < 1 || iResponse > 10 )
printf("\nNumber not in range\n");
else
printf("\nThank you\n");
}</source>
<pre class=codeResult>Enter a number from 1 to 10: 2

Thank you</pre>

==if Comparisons and Their Opposites==

if Comparison
else Statement Executed By This Condition
<
>=
==
!=
>
<=
<=
>
>=
<
!=
==

==if statement==

To conditionally execute statements, you can use the if or the if...else statement.
The general form of the if statement is

<source lang="cpp">if(expr) {
s1 ;
s2 ;
....
}</source>

==if statement: compare the value from user input==

<source lang="cpp">#include <stdio.h>
int main(void)
{
int number = 0;
printf("\nEnter an integer between 1 and 10: ");
scanf("%d",&number);
if (number > 5)
printf("You entered %d which is greater than 5\n", number);
if (number < 6)
printf("You entered %d which is less than 6\n", number);
return 0;
}</source>
<pre class=codeResult>Enter an integer between 1 and 10: 5
You entered 5 which is less than 6</pre>

==if statement with two else statements==

<source lang="cpp">#include <stdio.h>
#include <stdlib.h>

int main()
{
char num[2];
int number;

printf("Enter a number from 0 to 9:");
gets(num);
number=atoi(num);

if(number<5)
{
printf("That number is less than 5!\n");
}
else if(number==5)
{
printf("You typed in 5!\n");
}
else
{
printf("That number is more than 5!\n");
}

return(0);
}</source>
<pre class=codeResult>Enter a number from 0 to 9:2
That number is less than 5!</pre>

==If with else statement==

The general format for an if-else statement is

<source lang="cpp">if (condition)
simple or compound statement
else
simple or compound statement.</source>

==Operators Used in if Comparisons==

Comparison
Meaning or Pronunciation
"True" Example
<
Less than
1 < 5, 8 < 9
==
Equal to
7 == 7, 1 == 1
>
Greater than
7 > 5, 10 > 0
<=
Less than or equal to
4 <= 5, 8 <= 8
>=
Greater than or equal to
6 >= 5, 2 >= 2
!=
Not equal to
1 != 0, 1 != 3.99

==The if-else-if statement==

The general format for the if-else if statement is:

<source lang="cpp">if (condition 1)
simple or compound statement
else if (condition 2)
simple or compound statement
else if ( condition 3)
simple or compound statement
.....
else if ( conditon n )
simple or compound statement</source>

==The if statement: a compound statement==

If a compound statement is used, it must be enclosed in opening and closing braces.

<source lang="cpp">#include<stdio.h>
main()
{
int i=5, j =1;

if (i > j){
i = i + 1;
printf("%d",i);
}
else
j = j +1;
}</source>
<pre class=codeResult>6</pre>

==To execute only one statement, opening and closing braces are not required==

<source lang="cpp">#include <stdio.h>
main(){
int i = 5;
if(i > 0)
printf(" i > 0. \n");

}</source>
<pre class=codeResult>i > 0.</pre>

==Use compound conditions to check for upper and lowercase letters==

<source lang="cpp">#include <stdio.h>
main(){
char cResponse = "\0";
printf("Enter the letter A: ");
scanf("%c", &cResponse);
if ( cResponse== "A" || cResponse == "a" )
printf("\nCorrect response\n");
else
printf("\nIncorrect response\n");
}</source>
<pre class=codeResult>Enter the letter A: 1

Incorrect response</pre>

==Use isdigit Function in if statement==

<source lang="cpp">#include <stdio.h>
#include <ctype.h>
main()
{
char cResponse = "\0";
printf("\nPlease enter a letter: ");
scanf("%c", &cResponse);
if ( isdigit(cResponse)== 0 )
printf("\nThank you\n");
else
printf("\nYou did not enter a letter\n");
}</source>
<pre class=codeResult>Please enter a letter: 1

You did not enter a letter</pre>

==Using nested ifs==

<source lang="cpp">#include <stdio.h>
#include <limits.h>
int main(void)
{
long test = 0L;

if( test % 2L == 0L) {
printf("The number %ld is even", test);
if ( (test/2L) % 2L == 0L)
{
printf("\nHalf of %ld is also even", test);
printf("\nThat"s interesting isn"t it?\n");
}
}
else
printf("The number %ld is odd\n", test);
return 0;
}</source>
<pre class=codeResult>The number 0 is even
Half of 0 is also even
That"s interesting isn"t it?</pre>

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