Program control structures

If is a statement that checks the condition and executes the following statements if the condition is true. There are multiple ways how to write down the if statement:

//1st example
if (condition) statement;     
 
//2nd example
if (condition)
statement;                    
 
//3rd example
if (condition) { statement; } 
 
//4th example
if (condition)
{
  statement;
}                             

When both true and false cases of the condition should be viewed, the else part should is added to the if statement in the following ways:

if (condition) {
  statement1;    //executes when the condition is true
}
else {
  statement2;    //executes when the condition is false
}

If more conditions should be viewed, the else if part is added to the if statement:

if (condition1) {
  statement1;    //executes when the condition1 is true
}
else if (condition2) {
  statement2;    //executes when the condition2 is true
}
else {
  statement3;      //executes in all of the rest cases
}

The example when the x variable is compared and in the cases when it is higher than 10, the digitalWrite() method executes.

if (x>10) 
{
  digitalWrite(LEDpin, HIGH)  //statement is executed if the x>10 expression is true
}

Logical operators are widely used together with the condition operator if that is described below.

There are multiple comparison operators used for comparing variables and values. All of these operators compare the value of the variable on the left to the value of the variable on the right. Comparison operators are following:

• == (equal to) - if they are equal, the result is TRUE, otherwise FALSE.
• != (not equal to) - if they are not equal, the result is TRUE, otherwise FALSE.
• < (less than) - if the value of the variable on the left is less than the value of the variable on the right, the result is TRUE, otherwise FALSE.
• < = (less than or equal to) - if the value of the variable on the left is less than or equal to the value of the variable on the right, the result is TRUE, otherwise FALSE.
• > (greater than) - if the value of the variable on the left is greater than the value of the variable on the right, the result is TRUE, otherwise FALSE.
• > = (greater than or equal to) - if the value of the variable on the left is greater than or equal to the value of the variable on the right, the result is TRUE, otherwise FALSE.

Examples:

if (x==y){ //equal
  //statement
}
 
if (x!=y){ //not equal
  //statement
}
 
if (x<y){ //less than
  //statement
}
 
if (x<=y){ //less than or equal
  //statement
}
 
if (x>y){ //greater than
  //statement
}
 
if (x>=y){ //greater than or equal
  //statement
}

The Boolean logical operators

• ! (logical not) -
• && (logical and) -
• || (logical or) -

Switch…case