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The instructions that tell a computer what to do are written in machine code. Machine code is a series of numbers, written in either binary or hexadecimal. Each number represents a different instruction.

Programmers find machine code difficult to learn, program in and debug. As a result, the majority of programmers write programs in high level programming languages. These languages are close to the spoken and written language of the programmer. For example, Python uses 'print', ‘if’, 'input' and 'while' statements - all words from the English language - to form instructions. In fact, instructions often look like abbreviated English sentences.

Compare this simple Python program with its comments that are written in English:

while count < 10:

#While the value of count is less than ten

number = int(input("Type in a number"))

    #Input a number

total = total + number

    #Add the number to the total

count = count + 1

    #Add one to the value of count

print("The total is ", total)

#Print out the total

Programmers write in high level languages because they are easier to understand and are less complex than machine code. They allow the programmer to focus on what needs to be done, rather than on how the computer actually works.

For example, in many high level languages, to place a message on the screen, a programmer would use the statement 'print'. The programmer might not know how the computer actually generates the message. They just need to know how to use the 'print' statement.

High level languages have a disadvantage - they are restricted to the number of statements built into them. If the programmer wants a program to do something, but a statement does not exist to do so, the task cannot be done.

Commonly used high level languages

Many types of high level language exist and are in common use today, including:

• Python
• Java
• C++
• C#
• Visual Basic
• JavaScript

Source code

Any program written in a high level language is known as source code. Source code must be translated into machine code before the computer can understand and execute it.

High level languages are known as one-to-many languages as each high level instruction is translated into many machine code instructions.