Categories: All Variables and Constants  String manipulation  Builtin functions  Input and output  Arrays  Conditional logic  Repetition / Iteration  Functions / Procedures 

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This resource is designed as a quick reference or revision guide. It has not been endorsed by any exam boards. If you spot any mistakes, please let me know and I'll fix them asap.

Introduction

This website aims to give a quick reference for VB.NET, Python and C# and pseudocode and is aimed primarily at teachers & students working towards a GCSE or A Level in Computer Science

VB.NET, Python and C# are programming languages designed to be understood and followed by computers. Pseudocode is not a programming language: it's written to be understood by humans so that they can turn it into any programming language.

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Skill
Description
VB.NET
Python
C#
For loop
   

A for loop is a count-controlled loop which means it your code says exactly how many times the loop should repeat. 

A for loop will use a variable to count between the minimum and maximum value. This variable is called the index, which is why for loops often use the variable i.

A for loop is an example of definite iteration because the number of times the loop repeats is clearly defined.

This example will count from 10 to 20

for i in range(10,21): print(i)
for(int i = 10; i < 21; i++) { Console.WriteLine(i); }
For loop (with step)
   

A for loop is a count-controlled loop which means it your code says exactly how many times the loop should repeat. 

A for loop will use a variable to count between the minimum and maximum value. This variable is called the index, which is why for loops often use the variable i.

Rather than increasing the index by 1 each time, you can step up by any amount until you reach the maximum.

This example will count down from 10 to 1 then say "Blast off!" 

for i in range(10,0,-1): print(i) print("Blast off!")
for(int i = 10; i > 0; i--) { Console.WriteLine(i); } Console.WriteLine("Blast off!");
For Each loop
   

A for each loop means the code in the loop will run once for each item in an array.

This means it is a count-controlled loop because the number of times the loop will run is not dependent on a condition being met: you know how many times it will repeat in advance.

A for each loop is an example of definite iteration because the number of times the loop repeats is clearly defined.

This example will display the lyrics for "The wheels on the ... go round and round"  for an array containing the strings "bus", "car" and "tram"

vehicles = ["bus", "car", "tram"] for vehicle in vehicles: print("The wheels on the " + vehicle + " go round and round") print("Round and round, round and round") print("The wheels on the " + vehicle + " go round and round") print("All day long")
string[] vehicles = {"bus", "car", "tram"}; foreach (stringvehicle in vehicles) { Console.WriteLine("The wheels on the " + vehicle + " go round and round"); Console.WriteLine("Round and round, round and round"); Console.WriteLine("The wheels on the " + vehicle + " go round and round"); Console.WriteLine("All day long"); }

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