arrays and user defined function basics

array

special variable having one name, but storing a list of data items, with each item being directly accessible. Some languages use a construct similar to an array called a vector. Each item in an array is known as an element

• each element’s location number is called the index

array syntax

an array variable is an ordered list of items of a given data type and size. Each iteem in an array is called an element. For array x, each element is accessed as x[0], x[1]… In an array access, the number in brackets is called the index of that element

• array indices start with 0 rather than 1

array summary

• An array variable stores multiple items, each accessible using an index. In contrast, a scalar variable stores just one item.

• Array indices start from 0, not 1. An index may be represented as an expression.

basics of functions

• a function is a named list of statements

• a function definition consists of the new function’s name and a block of statements. The function’s name can be any valid identifier

• a function call is an invocation of a function’s name, causing the function’s statements to execute

• a local variable is a variable declared in a function, which is then accessible only within that function

parameters

• a programmer can influence a function’s behavior via an input

• an argument is a value provided to a function’s parameter during a function call

• a parameter is like a variable declaration. Upon a call, the parameter’s memory location is allocated, and the parameter is assigned with the argument’s value. Upon return, the parameter is deleted from memory

returning a value from a function

a function may return one value by assigning a return variable with the return value

modular and incremental program development

programmers commonly use functions to write programs modularly and incrementally

• modular development is the process of dividing a program into separate modules that can be developed and tested separately and then integrated into a single program

• incremental development is a process in which a programmer writes and tests a few statements, then writes and tests a small amount more (an incremental amount), and so on

• a function stub is a function definition whose statements have not been written yet

• a programmer can use function stubs to capture the hgih level behavior rof the main function and the required functions before diving into the details of each function

function definition

in coral this begins with the word Function, the function’s name, and a list of comma-separated parameters in parentheses and a return indication. The parentheses are required even if no parameters exist. The function’s slocal variables and statements start on the next line and are indented

function call

consists of the function name and parentheses, within which comma-separated arguments appear. A program’s execution starts by calling the Main() function, which may itself call other functions

functions summary

• A function is a named list of statements.

• A function definition consists of the new function's name and a block of statements. The function's name can be any valid identifier.

• A function call is an invocation of a function's name, causing the function's statements to execute.

• A program's execution begins with the Main function.

• A programmer can influence a function's behavior via an input. A parameter is a function input specified in a function definition. An argument is a value provided to a function's parameter during a function call.

• A parameter is like a variable declaration. Upon a call, the parameter's memory location is allocated, and the parameter is assigned with the argument's value.

• A function may return one value by assigning a return variable with the return value.

• A function call evaluates to the returned value. Thus, a function call often appears within an expression.

• Decomposing a program into functions can greatly aid program readability, helping yield an initially correct program, and easing future maintenance.

• Programmers commonly use functions to write programs modularly and incrementally.

• Modular development is the process of dividing a program into separate modules that can be developed and tested separately and then integrated into a single program.

• Incremental development is a process in which a programmer writes and tests a few statements, then writes and tests a small amount more (an incremental amount), and so on.

• A function can be defined once, then called from multiple places in a program, thus avoiding redundant statements.

• The skill of decomposing a program's behavior into a good set of functions is a fundamental part of programming that helps characterize a good programmer.

• Each function should have easily-recognizable behavior, and the behavior of the Main function (and any function that calls other functions) should be easily understandable via the sequence of function calls.

• A function's statements may include branches, loops, calls to other functions, and other statements.