Lab6 Function Pt1 CSEB114 Sem2 20112012.

8/11/2019 Lab6 Function Pt1 CSEB114 Sem2 20112012.

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C Programming LabUniversiti Tenaga Nasional

6 Function (Part I)

Do you still remember this?

#.()

("")

Referring to the same program but through function, your program might look somethinglike this:

#.

()

()

()

()

("")

Some recap from lecture: A function is a module (or block) in program code that deals with a particular task. Two purposes of using a function: -

To allow a program to say:This piece of code does a specific job which stands by itself and should not bemixed up with anything else

Function allows a block of codes to be reused

Function helps us to organise a program in a simpler way.

The difference between looping and function is:

A function can be called at any part of a program but a loop can only be done orused at the looping statement in a program.

3 elements of function are:1. Definition- a set of instructionsthat a function is supposed to do /execute.2. Prototype- Like variable, a function must also be declaredbefore using in a

program. This declaration is referred as function prototype.3. Function call- The execution part of a function (function call) must be instructed

or called by other function. Function main ( ) normally acts as the caller function.Anyway, it can be called from other functions too. Function will return any value (if

theres a return value) to the caller function after it has finished executing its taskin the called function.

Block of codesfor function

main()

Block of codesfor functionprint()


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#. ()

()

()

()

("")

Looking at function prototype in detail:

()

Looking at function call in detail:

()

Looking at function definition in detail:

()

Function prototype

Function call

Function definition

The datatype of

thereturn

Functionname

The data typeof the

parameter(s)

Functionname

Value(s) to be passed tothe corresponding

function

Variablethat will

accept thereturnvalue

Functionname

Variable list (data typeand variable name

separated by comma)

The datatype of the

returnvalue


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How does function work? Lets modify the previous example.

#. ()

()

()

(" ' ")()

()

("")

As you can see, the difference between looping and function is: A function can be called atany part of a program but a loop can only be done or used at the looping statement in aprogram.

Types of functions:

Receive no input parameter and return nothingSample program without function Sample program with function// 1#.

()

("")

// 2#.

()

()

()

()

("")

Receive no input parameter and return a value

Sample program without function Sample program with function

// 3#.

()

(" :")("%",&)(" %",)

// 4#.

()

()

( )(" %", )

()

(" :")

("%",&)

12

34


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Receive input parameter and return nothing

Sample program without function Sample program with function

// 5#.

()

15 + 8

(" % ",)

// 6#.()

()

15 + 8()

()

(" % ",)

Receive input parameter and return a value

Sample program without function Sample program with function// 7#.

()

, 1, 2(" ")

("%%", &1, &2) 1 + 2(" %", )

// 8#.

(,)

()

, 1, 2

(" ") ("%%", &1, &2)

(1, 2)(" %", )

(1, 2)

1 + 2

How to create program with function?

Sample question:

Write a program that has a function multiplythat accept 2 integers and returns themultiplication of those two integers.

One of the methods to create function:

1 Create the skeleton of function main()2 Develop the function definition (instruction in the function, function name,

parameters, return value)3 Set the function call, based on the function definition

4 Fill in other stuff in function main()(variable declarations, other instructions)5 End with function prototype


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Refer to sample 8. Create as many function(s) as you can from the program

Another method:

1 Create full program without function (except for function main())2 Select and extract part(s) that want to be converted to function

3 Create function(s)

Exercise:

Write a main()function and another function, named message()that main()calls. Ask

the users for their annual income in main()function. Pass the value of income from

main()function to the message()function where message()function will print acongratulatory message if the user makes more than RM40,000 a year or an encouragementmessage if the user makes less.

Lab6 Function Pt1 CSEB114 Sem2 20112012.

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