Procedures & functions

A function is a named block

• A function is a named block of code you can run again and again.
• Define it once with def, then call it by name.
• This avoids repeating yourself and keeps programs tidy.

def greet():
    print("Hello!")

greet()
greet()

Parameters pass data in

• A parameter is a value the function receives.
• Put it in the brackets, and pass an argument when you call.
• IGCSE allows up to three parameters.

def greet(name):
    print("Hello, " + name)

greet("Ada")
greet("Sam")

Functions return a value

• A function hands a value back with return.
• A block that only does something and returns nothing is a procedure.

def square(n):
    return n * n

answer = square(6)
print(answer)        # 36

In the exam: PROCEDURE and FUNCTION

• Pseudocode separates a PROCEDURE (no result) from a FUNCTION (returns a value).

FUNCTION Square(N : INTEGER) RETURNS INTEGER
    RETURN N * N
ENDFUNCTION

Common mistakes

• A function returns a value with return; a procedure just does a job.
• Call it with ().
• Parameters receive the arguments in order.

Now you try

• Write each function — it is then called for you in the check.
• Press Check answer to test your code.