GCSE Computer Science
Component 2
2.2 Programming Fundamentals
- Variables, constants, operators, inputs, outputs and assignments
- Sequence, selection and iteration
- Arithmetic and boolean operators
- Data types
Variables, constants, operators, inputs, outputs and assignments
- Variable- points to a named section of memory where a value is stored. The value can change during the program’s execution.
- Constant- points to a named section of memory where a value is stored. The value cannot change during the program’s execution.
- Assignment— the process of storing a value in a variable / constant. Performed with the equals sign (=) when programming.
- Operators- perform a calculation e.g. +, -, *, /, MOD, DIV.
- Inputs- enters data into the program.
- Outputs- displays the results of processing.
Sequence, selection and iteration
Sequence
Instructions are executed in order from top to bottom until told to stop. This is the basic way that programs work.
| EXAM REFERENCE LANGUAGE |
print("These instructions will...")
print("execute in order...")
print("one after another.")
print("This is sequence.") |
| PYTHON |
print("These instructions will...")
print("execute in order...")
print("one after another.")
print("This is sequence.") |
| C# |
Console.WriteLine("These instructions will...");
Console.WriteLine("execute in order...");
Console.WriteLine("one after another.");
Console.WriteLine("This is sequence."); |
Selection
The program will branch to a different section depending on the result of a comparison. In simple terms — this is an IF statement. Many languages have an alternative statement called a switch statement.
| EXAM REFERENCE LANGUAGE |
if dog == "poodle" then
print("That's a cute dog.")
else
print("I prefer poodles.")
endif |
| PYTHON |
if dog == "poodle":
print("That's a cute dog.")
else
print("I prefer poodles.") |
| C# |
if (dog == "poodle") {
Console.WriteLine("That's a cute dog.");
}
else {
Console.WriteLine("I prefer poodles.");
} |
Iteration
A section of the program is repeated either a certain number of times or until a condition is no longer true. In simple terms this will be either a FOR loop or a WHILE loop.
| EXAM REFERENCE LANGUAGE |
for i = 0 to 10
print("Hello")
next i
while answer != "learncomputing"
answer = input("What is the password?")
end while |
| PYTHON |
for i in range(0, 11):
print("Hello")
while answer != "learncomputing":
answer = input("What is the password?") |
| C# |
for(int i = 0; i < 11; i++) {
Console.WriteLine("Hello");
}
while (answer != "learncomputing") {
Console.WriteLine("What is the password?");
answer = Console.ReadLine();
} |
Arithmetic and boolean operators
| Operator | Meaning |
|---|---|
| = | Assigns a variable a value |
| == | Compares two values to see if they are equal |
| != | Compares two values to see if they are not equal |
| * | Multiply |
| - | Subtraction |
| + | Addition |
| / | Divide |
| MOD | Give the remainder of a division |
| DIV | Give just the whole number part of the answer of a division |
| < | Less than |
| <= | Less than or equal to |
| > | Greater than |
| >= | Greater than or equal to |
Data types
| Unit | Data type | Alternative names |
|---|---|---|
| Integer | A whole number e.g. 7 | |
| Real | float, single, double, decimal | A number with a decimal point e.g. 7.4 |
| Character | char | A single character e.g. B |
| String | A collection of characters e.g. "Learn Computing" | |
| Boolean | bool | A special data types that can only be either True or False |
Casting
The process of converting one data type to another. See below example of casting to an integer and string.
| EXAM REFERENCE LANGUAGE |
number = input("What number would you like?")
number = int(number)
print("The number was " + str(number)) |
| PYTHON |
number = input("What number would you like?")
number = int(number)
print("The number was " + str(number))) |
| C# |
Console.WriteLine("What number would you like?");
int number = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("The number was " + Convert.ToString(number)); |