C If ... Else Examples
Real-Life Examples
This example shows how you can use if..else to "open a door" if the user enters the correct code:
Example
int doorCode = 1337;
if (doorCode == 1337) {
printf("Correct
code.\nThe door is now open.");
} else {
printf("Wrong code.\nThe
door remains closed.");
}
Try it Yourself »
This example shows how you can use if..else
to find out if a number is positive or negative:
Example
int myNum = 10; // Is this a positive or negative number?
if (myNum >
0) {
printf("The value is a positive number.");
} else if (myNum
< 0) {
printf("The value is a negative number.");
} else {
printf("The value is 0.");
}
Try it Yourself »
Find out if a person is old enough to vote:
Example
int myAge = 25;
int votingAge = 18;
if (myAge >= votingAge) {
printf("Old enough to vote!");
} else {
printf("Not old enough
to vote.");
}
Try it Yourself »
Find out if a person is old enough to vote, and if they are a citizen (using nested if statements):
Example
int age = 20;
bool isCitizen = true;
if (age >= 18) {
printf("Old enough to vote.\n");
if (isCitizen) {
printf("And you are a citizen, so you can vote!\n");
} else {
printf("But you must be a citizen to vote.\n");
}
} else {
printf("Not old enough to vote.\n");
}
Find out if a number is even or odd:
Example
int myNum = 5;
if (myNum % 2 ==
0) {
printf("%d is even.\n",
myNum);
} else {
printf("%d is odd.\n", myNum);
}
Try it Yourself »
Check temperature (Celsius):
Example
int temperature = 30;
if (temperature < 0) {
printf("It's
freezing!\n");
} else if (temperature < 20) {
printf("It's
cool.\n");
} else {
printf("It's warm.\n");
}
Try it Yourself »
System access control example - You must be logged in, and then you either need to be an admin, or have a high security clearance (level 1 or 2) to get access:
Example
bool isLoggedIn = true;
bool isAdmin = false;
int securityLevel = 3; // 1 = highest
if (isLoggedIn && (isAdmin || securityLevel <= 2)) {
printf("Access granted\n");
} else {
printf("Access denied\n");
}
// Try changing securityLevel and isAdmin to test different outcomes:
// securityLevel 1 = Access granted
// securityLevel 2 = Access granted
// securityLevel 3 = Access denied
// securityLevel 4 = Access denied
// If isAdmin = true, access is granted.
