Sub Programs

Sub programs are smaller, reusable blocks of code that are used to structure larger programs. They allow you to break down complex problems into smaller, manageable tasks. The two main types of sub programs are functions and procedures.

Functions and Procedures

• Functions and procedures both help to create structured code by organizing logic into independent blocks.
• Functions return a value after performing a task, whereas procedures do not return a value. | Type | Definition | Example | |---|---|---| | Function | A sub program that returns a value. | function triple(number)
return number * 3
endfunction
  Calling: y = triple(7) | | Procedure | A sub program that performs a task but does not return a value. | procedure greeting(name)
print("Hello " + name)
endprocedure
  Calling: greeting("Hamish") |

Using Sub Programs Effectively

• Functions and procedures can be used to improve code structure by avoiding repetition, making the program easier to read and maintain.
• They allow modular programming, where each part of the program does one thing and can be reused in different contexts.

Where to Use Sub Programs

• When performing repetitive tasks to avoid code duplication.
• To break down a complex problem into simpler, smaller tasks.
• When returning a specific result (use a function) or just executing a task without needing a return value (use a procedure).

Local and Global Variables

Sub programs can use two types of variables:

• Local variables/constants: Declared inside a sub program and only accessible within it. These are useful for keeping data isolated to avoid conflicts with other parts of the program.
• Global variables/constants: Declared outside any sub program and accessible throughout the entire program. Be cautious when using global variables as they can cause unintended side effects if modified unexpectedly.

Arrays in Sub Programs

Arrays can be passed to and returned from sub programs, allowing the manipulation of multiple values at once:

Passing an Array

Arrays can be passed into sub programs as arguments, allowing you to perform operations on large sets of data.

Example:

procedure printNames(names)
    for name in names:
        print(name)
endprocedure

Calling: printNames(["Bob", "Alice", "Eve"])

Returning an Array

Functions can also return arrays, which allows them to process and return multiple values at once.

Example:

function getMultiples(numbers)
    for i in range(0, len(numbers)):
        numbers[i] = numbers[i] * 2
    return numbers
endfunction