Why subprograms

301.12 Subprograms

Subprograms — Note 1 of 4

Reasons to split code.

What you need to know

Subprograms (functions and procedures) break code into reusable, named blocks. This makes programs shorter, easier to read, test, and maintain.

What to know

Avoid repeating the same code — write it once, call it many times
Each subprogram does one clear job
Easier to test each part independently
Makes the main program shorter and more readable

Code examples

Why use subprograms

python

# Without subprogram: repeated code
print("="*20)
print("Welcome")
print("="*20)

# With subprogram: reusable
def show_header():
    print("="*20)
    print("Welcome")
    print("="*20)

show_header()

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Specification notes for programming are in Paper 2.