Functions and Libraries

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A lot of these definitions a notes are very interrelated. It is recommended that you read this twice and see the Tracing Functions page.

Functions

Function

a define block of coding able to be used in other blocks of code

This also goes under possible names of method or sub method.
Technically a function is suppose to return a value while a method just performs an action.

Function Header

the name of a function plus other modifiers such as return type and parameters

Call

to use a function in coding

This is also known as invoking.

Return

a function returns a value

A bit redundant, well think of this. If a function returns an integer, a call to that function can be treated as a constant integer. So the function can be used in things like assignment.

void

a function return type that specifies that there is no return value

Overload

to define a function with the same name but with different parameters

Default

to assign a value in a function parameter if no actual parameter is passed

Main

a function often used to run the entire program

Yes you have been writing functions all along. Main is a function that is the program.

Variable Sight and Life

Scope

the range in which a variable can be accessed by a function

Keep in mind each programming language has their own idea of scope.

Life

the range in which a variable exists while a program is running

Global scope

to be able to be accessed by all functions

Global Variable

a variable with global scope that exists from the beginning till the end of a program

Often these are declared outside of all functions.

Local Variable

a variable with scope of only the function they are defined in and only exists from when they are declared till the end of the function they are declared in

Static Variable

a variable that exist from its declaration till the end of a program

You don't use or see these variable often in basic computer science, unless they are important in a language e.g. Java.

Parameters

Parameters

variables that a function receives for processing

There are a lot of terms for describe parameters.
There are two types of parameters.
There are four ways to pass variables are parameters.

Formal Parameter

the variable of the parameter of a function

Actual Parameter

the variable used to call the function

This is also known as an argument.

Pass

to transfer information of the actual parameter to the formal parameter

Pass by Value

a parameter passes the value of the actual parameter

In this type of passing a whole new variable is declared in a function with the same value as the original.
This is useful if you want the original variable unchanged and the variable uses little memory e.g. int

Pass by Reference

a parameter passes the memory address/location of the actual parameter

In this type of passing a reference to the original variable is passed.
This this means that whatever is done to the variable inside a function also happens to the actual variable outside the function.

Constant Pass by Reference

a parameter that is passing by reference but is made constant

Here a reference is passed but the variable inside the function is constant (unchangeable).
Why not pass by value? Since some variable take up a lot of memory space e.g. objects it is better to not create a whole new variable a use memory. In the end the program runs faster.

Pass by Text

a parameter passes the text of a variable

Here text is passed...think of assigning a block of code to a variable, so every time that variable occurs in the function you copy and paste that block of code.
This type of passing is uncommon and exists in older programming languages. Only useful in trivia.

Specification Documentation

Precondition

a condition that must be true for a function to be called properly

This is often a comment under or over a function header.

Postcondition

a condition that exist after the function is called

This either tells what a function returns or what it changes e.g. message printed to the screen
This is also a programming comment with the precondition.
Unlike the precondition there always must be a postcondition.

Libraries

Library

a file or group of files with defined functions that a program can include so its function can be used

Other various forms of libraries are packages and modules (but they are programming language specific).
This is also known as a header file.
Often there is a basic set of libraries included in every language, e.g. iostream for C++.

Current

the folder/directory where the code source file, programming project file, executable file, or byte code file is

Include

the folder/directory where basic/default library files are