Discover How to Build Programs With Algorithms

As humans, we’re able to differentiate between  12  , a number, and  hello  , a word written with letters. However, computers can’t work this out on their own. At least, not without some help from us—we have to tell the computer what type of value it’s dealing with so it can read and understand it. Providing the type of a variable gives the computer the information it needs on a number of parameters, such as:

• Its size

• The memory layout of the variable

• The range of values that can be stored in the memory

• The operations that can be applied to the variable

A type is a data classification which tells the computer how the programmer wants to use the data.

There are many types of variables, and so far we’ve only come across one of them—numbers. But other types of data can also be used, such as words and booleans, two types which are frequently used in programming.

You can’t divide a word by five, for example, or put a number in capitals! But computers can’t tell the difference between the two data types, and this is why we have to assign types to the different concepts we use in a program.

Think of it like a LEGO set. Some pieces are flat and wide for building the base of a structure, and others are round to make a mast or door hinges, etc. Certain pieces have specific uses, but they’re all LEGO!

Learn About Numbers

Just like in math, there are different sorts of numbers, which can be integers (with no decimal point) or floats (with a decimal point).

Integers: 1, 5, 10. Decimals: 1.3, 1.7777, 2.3.

Learn About Strings

A string is made up of a set of characters, which can include spaces and figures. For example, “a,” “Algorithm,” and “I have two brothers.”

Learn About Booleans

Last, but not least, we have a type of data which provides a “True” or “False” answer. Think of it like a switch, or the two sides of a coin.

To use conditions, of course! When you check a condition, the information provided as a response is a boolean type.

You can now add this information in the variables declaration section, adding the type after the variable.

This is what it looks like in the pseudocode:

Type algorithm
Variable
   wholeNumber ← 0 : INTEGER
   floatingPointNumber ← 0.0 : FLOAT
   string ← “” : STRING
   boolean ← False : BOOL

As you can see, not much changes in the declaration of variables—all you need to do is write a colon  :  and then the type of the variable.

Over to You!

Context

This exercise is based on the following algorithm, which calls the  moveStartEnd  function, which moves the player from Start to End automatically:

Maze algorithm
Start
   moveStartEnd()
End

Instructions 

You’ll need to create two variables:

• The first saves the name of the player.

• The second states whether the player has finished the maze.

Also, the  moveStartEnd  function needs to take the name of the player as a parameter to work properly.

Your Mission

1. Declare the  playerName  variable, initialize it, and add the type of data.

2. Declare the  maze_completed  variable, initialize it to false, and add the type of data. 

3. At the start of the algorithm, assign your name to the  playerName  variable.

4. Add the  playerName  variable as a parameter of the  moveStartEnd  function.

5. Change the value of the  maze_completed  variable if necessary in the algorithm.

Check Your Work

Here’s what the result of this exercise should look like:

Maze algorithm
Variable
   playerName ← "" : STRING
   maze_completed ← False : BOOL
Start
   playerName ← "Kurt"
   moveStartEnd(playerName)
   maze_completed ← True
End

Let’s Recap!

• A variable can be considered as a memory location that can contain values of a specific type.

• Each variable has a specific type, which corresponds to the type of data it can contain.

• There are different types for storing numbers, strings, and booleans. 

• The type of a variable can be provided in the  variable  section of the pseudocode to provide more information on the variable. 

Now you’re familiar with the different types of data, you’ll never assign the wrong type to your variables again! This is crucial for the next bit of the program, and especially when it comes to what you want to do with these variables. In the next chapter, we’ll see how to determine whether certain instructions are launched or not, using conditional structures.