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Computer Science · Class 10 · Chapter 12: Functions

8 min

Key points

Function is a sub-program or sub-routine that performs a specific task and can be called from the main program
Functions reduce program length, avoid repetition of code, and make programs easier to understand and debug
There are two types of functions: Built-in functions (provided by C language) and User-defined functions (created by programmer)
Function declaration tells the compiler about function name, return type, and parameters
Function definition contains the actual code that executes when function is called
Function call is used to execute the function from main program or another function
Return statement sends value back to the calling function
Parameters are values passed to function while arguments are actual values received by function

Definitions

Function: A function is a sub-program or sub-routine that performs a specific task and can be called from the main program or from another function
Function Declaration: Function declaration tells the compiler about the function name, return type, and parameters but does not contain the function body
Function Definition: Function definition contains the actual statements or code that executes when the function is called
Built-in Functions: Built-in functions are pre-defined functions provided by C language such as printf(), scanf(), sqrt(), pow() etc.
User-defined Functions: User-defined functions are created by the programmer according to program requirements to perform specific tasks

Worked example

Define function and determine whether the relation f = {(1,2), (2,4), (3,6), (4,8)} is a function or not. Also find its domain and range. (5 marks)

Definition: A function is a relation in which each element of the domain is paired with exactly one element of the range. Checking the relation: Each input value (1,2,3,4) maps to exactly one output value, so this is a function. Domain = {1,2,3,4}, Range = {2,4,6,8}

Common mistakes

Students often confuse function declaration with function definition
Forgetting to write return statement in functions that return values
Not matching parameter types in function declaration and definition
Writing function call without proper arguments
Confusing built-in functions with user-defined functions in examples

Quick recap

A function is a special relation where each domain element maps to exactly one range element. Remember the vertical line test for graphs - if any vertical line intersects the curve more than once, it's not a function. Types include one-to-one (injective), onto (surjective), and bijective functions. Always write domain and range in proper set notation.

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