programming iii (mblock)plk83.edu.hk/cy/mblock/programming iii (mblock).pdf · 2016. 6. 30. · 2....

Computer Literacy Programming III (mBlock)

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Programming III (mBlock) http://www.plk83.edu.hk/cy/mblock

Contents

1. Introduction (Page 1)

2. IPO Model (Page 2)

3. Variable (Page 2)

4. Operators (Page 3)

5. Decision Making (Page 5)

6. Loops (Page 8)

7. Block (Page 12)

Introduction

A computer program is a collection of instructions that performs a specific task when executed

by a computer.

Script language is a programming language that supports program (called a ‘script’) written

for a special run-time environment.

The following script contains 4 instructions that should be executed under the run-time

environment of mblock (http://www.mblock.cc/) only.


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IPO Model

A program using the input-process-output (IPO) model receives inputs from a user or other

sources, does some computations on the input, and outputs the results of the computations.

Try the following example.

Describe the input, process and the output of the above script.

Input: __________________________________________________________________

Process: __________________________________________________________________

Output: __________________________________________________________________

Variable

The input of the instruction is stored in the variable

.

You can make a new variable (named as ‘age’) as below.

Then, execute the following script to store the input into the variable ‘age’.

In addition, you can set and change the value of the variable.


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Activity 1

Design a script to output the sum of two inputted integers as below.

Operators

There are different kinds of operators.

Arithmetic Operators

perform ‘addition’, ‘subtraction’, ‘multiplication’ and ‘division’ respectively.

State the instructions to calculate the followings.

1. (2 * 3 + 4) / 5 ___________________________________________________________

2. 2 * 3 + 4 / 5 ___________________________________________________________

Check your answers by using the instruction.


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Relational Operators

perform ‘less than’, ‘equal to’ and ‘greater than’ comparisons respectively.

The results can be either ‘true’ or ‘false’.

State the results of the followings.

1. 6 < 8 ___________

2. 4 = 4 ___________

3. (5 + 6) > 7 ___________

Check your answers by using the instruction.

Logical Operators

perform ‘and’, ‘or’ and ‘not’ operations respectively.

The results can be either ‘true’ or ‘false’.

The following ‘truth tables’ describe the relationships between the inputs and outputs of

various logical operators.

Inputs Output Inputs Output Input Output

P Q P and Q P Q P or Q P not P

true true true true true true true false

true false false true false true false true

false true false false true true

false false false false false false

Activity 2

Design a script to meet the following requirements.

1. Generate two random numbers between 1 and 10. The first number should be less than or

equal to the second number.

2. Input an integer.

3. If the input is within the two random numbers, output ‘true’. Otherwise, output ‘false’.


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Decision Making

There are two popular decision making structures.

if-then

This structure requires that the programmer specifies the condition to be tested by the program,

along with a statement or statements to be executed if the condition is determined to be true.

If the condition is determined to be false, nothing will be executed.

if-then-else

This structure requires that the programmer the condition to be tested by the program, along

with a statement or statements to be executed if the condition is determined to be true, and

other statements to be executed if the condition is determined to be false.


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Example

In the given script, if the input is larger

than 100, the output is “Too large!”.

Otherwise, the mark is outputted.

Nested If structure

One if structure may itself contain another if structure.

The following shows some possible nested if structures.

Example

The first condition to be tested is

. If it is true,

is

executed. Otherwise, the second

condition is

tested and execute one of the last two

“say” instructions according to the

results of the second condition.


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Activity 3

Design a script to give the appropriate feedback as below.

Activity 4


1. Input an integer.

2. If the integer is an odd number, output “It is an odd number”. Otherwise, output “It is an

even number”.

Hint: Use the instruction to find the remainder when the dividend is divided

by the divisor.

For example, returns 1; returns 0.

Activity 5

The following table shows the ticket prices of a theme park.

Ticket price (HK$)

Children (age: 3 - 17) $100

Adults (age: 18 - 60) $350

Others $0


1. Input the age.

2. Output the corresponding ticket price.


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Loops

If some instructions needs to be executed again and again, a loop structure can be used.

There are different kinds of loops.

Forever Loop

The instructions will be executed endlessly.

Given that number is a variable, what will

happen when the following script is

executed?

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Repeat Loop

We can specify the number of times to execute the loop.

Given that number and sum are two variables,

complete the following script to find the sum of

integers from 1 to 100.

Note: the output should be 5050.


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Repeat-until Loop

At the end of each loop, the condition is tested. If it

is false, the loop continues; if it is true, the loop

stops.

Example

Giving that number is a variable, the following script

performs a countdown from 10 to 0.

Wait-until Loop

This is special form of repeat-until loop in which there is nothing inside the loop. The function

of the wait-until loop is to pause the script until a specified condition is true.

Example

The following script gives a 3 seconds delay to the execution of the ‘say’ instruction by using

the built-in timer.


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Activity 6

Paint the backdrop with an ‘M’

shaped route and a red coloured circle

acts as the finished spot.

Insert a ‘Star’ shaped sprite. Shrink

the sprite such that it is inside the

route.

Design a script to meet the following

requirements.

1. Touch the Star to start the game.

2. The star can follow the movement

of the mouse pointer.

3. If the star is outside the route, a

warning sound will be played and the game failed. The star should go back to the starting

position.

4. If the star can reach the finished spot, you can win the game. An appropriate message

should be given.

Hint: You may use the following instructions to construct the script.


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Activity 7

Insert two paddles (by modifying the

size of the built-in button sprite) and a

ball onto the stage.

Make two variables Player_1 and

Player_2 to store the scores.

Two players can use the keyboard to

move the paddles up and down.

If the opponent cannot hit the ball, a

player can get one mark. The first player

who can get 5 marks is the winner.

For the upward movement control of the

paddle, which of the following sprits is

better? Why?

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Design the scripts for all the sprites.

Hint: You may use the following instructions to construct the script of the ball.


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Block

You can define a block to store a set of instructions. The following figure shows how a block

(named as ‘jump’) is defined.

Hence, you can assign the instructions to the block.

Then, you can execute the block.

In order to control the height in the block, add a number input (named as ‘height’).

Then, modify the block as below.


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Now, you can execute the block of instructions with different number inputs.

Activity 8

Pythagoras Theorem states the

relationship of three sides of a right

angled-triangle.

Design a block to find the hypotenuse c

from the inputs of a and b.


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Activity 9

Flappy bird is a popular game. You have to design the game to meet the following requirements.

1. The bird has to fly through the gaps between the tubes.

2. Use the keyboard to control the upward and downward movements of the bird.

3. The positions of the gaps should be randomly generated.

4. The tubes are moving towards the L.H.S. of the stage.

5. One mark is scored when the bird can fly through one gap.

6. If the bird touches any tube, the game is over.

Hint: The following script makes one of the tubes moving towards the L.H.S and the tube will

come out at a random position.

programming iii (mblock)plk83.edu.hk/cy/mblock/programming iii (mblock).pdf · 2016. 6. 30. · 2....

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