How to Use Programming Constructs in C

A construct is a line of code that performs a specific task under a specific condition, this may include if, if/else, elseif statements, while, for loops and many more.

Conditional Statements

If Statement

Here is an example of the If Statement:

int condition = 1;

if(condition == 1){
    Serial.println(condition);
}

Serial Monitor

1

The code inbetween the parenthesis of if() is known as the condition, hence the name Conditional Statement. In order for the code within the statement to be executed, the condition has to be true, the condition can range from comparing integers, booleans and even characters!

Examples

Here are some examples that will print out yes

int exampleOne = 1;
bool exampleTwo = true;
char exampleThree = 'a';

if(exampleOne == 1){
    Serial.println("yes");
}
if(exampleTwo == true){
    Serial.println("yes");
}
if(exampleThree == 'a'){
    Serial.println("yes");
}

Here are some examples that will not print out yes

int exampleOne = 1;
bool exampleTwo = true;
char exampleThree = 'a';

if(exampleOne == 3){
    Serial.println("yes");
}
if(exampleTwo == false){
    Serial.println("yes");
}
if(exampleThree == 'y'){
    Serial.println("yes");
}

If/Else Statement

The If/Else Statement can be dissected into 2 parts, the If Statement and the Else Statement. Here is an example of the If/Else Statement:

int condition = 1;

if(condition == 2){
    Serial.println("nothing");
}else{
    Serial.println(condition);
}

Serial Monitor

1

In the code above, the program will not execute the command within the If Statement as (condition == 1) is false, however, with the Else Statement, the program will instead execute the code within the Else Statement, printing out 1.

Else If Statement

The Else If Statement is an Else Statement but with another If Statement. Essentially, the Else If Statement adds another condition to the Else Statement. If the condition is false, the program will move on to the next Else Statement.

int condition = 1;
int elsif = 2;
int ans = 3;

if(condition == 2){
    Serial.println(condition);
}else if(elsif == 3){
    Serial.println(elsif);
}else{
    Serial.println(ans);
}

Serial Monitor

3

Since the If Statement's (condition == 2) and Else If Statement's (elsif == 3) are false, the program will print out 3.

Case-by-Case

The case-by-case construct starts off by comparing a condition, if the condition matches the constant value or expression, the program will execute the task within the code. Here is an example:

char choice = 'n';

switch(choice)
{
case 'Y':
case 'y':
       Serial.println("yes");
       break;
case 'N':
case 'n':
       Serial.println("no");
       break;
default:
       Serial.println("neutral");
}

Serial Monitor

no

The code above compares the choice of 'Y', 'y', 'N' and 'n'. If choice does not follow any of the characters mentioned, the code will execute the code within default.

If the condition type (choice) matches the constant type (char), in this case being character, the code within the case-by-case construct will be executed.

Think of case as an If Statement. If the variable given matches with the condition written after case, the code within will be executed, if not, the program will skip over the code and go on to the next case. If none of the case conditions match the given variable, the program will execute the code within default:.

The break; that exists at the end of ever block of code is a command that causes the program to skip the case-by-case construct entirely.

Loops

While Loops

A While Loop is used to repeat a specific block of code until the condition is no longer true. Here is an example:

int condition = 0;

while(condition <= 5){
    Serial.println(condition);
    condition++;
}

Serial Monitor

0
1
2
3
4
5

The While Loop shown above has the condition of (condition <= 5) and with every loop, condition++;, when condition = 6, the condition of (condition <= 5) will no longer be true, therefore ending the loop. (Note: This is not the only use of the while loop)

Do While Loop

The Do While Loop executes the code at least once and will continue executing the code as long as the condition is true. here is an example:

int seq = 3;
int condition = 2;

do{
    Serial.println(seq);
}while(condition == 1);

Serial Monitor

3

In this example, since condition == 1 is false, only the code within do{} will be executed. If condition == 1 is true, the code will look like:

Code

int seq = 3;
int condition = 2;

do{
    Serial.println(seq);
}while(condition == 2);

Serial Monitor

3
3
3
3
3
3
3
...

For Loop

The For Loop is used to repeat a block of code for a certain amount of time, keep in mind, this is different from the Arduino's loop() function. Here is an example:

for(int i = 0; i<5; i++){
    Serial.println(i);
}

Serial Monitor

0
1
2
3
4

Let's break down the For Loop into 3 parts, each part will be seperated by a ;.

Declaring the Variable

The first part of the For Loop is the declaration of a variable, commonly declared as i. To declare the variable i, the loop must include int i = 0;. (Note: The value of i can be whatever you want)

Condition

The second part of the For Loop is how many times you want the code within the loop to be repeated.

i=0	i<5	i++
0	✓	0+1 ✓
1	✓	1+1 ✓
2	✓	2+1 ✓
3	✓	3+1 ✓
4	✓	4+1 ✓
5	✕	5+1 ✕

As seen in the chart above, the loop would continue on until i=5, in which case, causes i<5 to be false, therefore ending the loop.

Increments

The third part of the For Loop is what will happen to the variable i after a singular loop has finished. As shown in the previous lesson, i++; means i=i+1. For every time the code within the loop gets executed, the integer i will have its value be increased by 1. (Note: The increment of i does not have to be i++, it could be anything you can do with an integer)

Conditional Expression

The Conditional Expression is extremely similar to how the If Else Statement works. Here is an example:

char s = 2 > 1 ? 't' : 'f';
Serial.println(s);

Serial Monitor

t

Conditional Expression:

condition ? operand : operand

The first operand of the expression is what the code will do if the condition is true, the second operand is what the code will do if the condition is false.