Convert a positive decimal number to a binary number

Challenge Level: Ready to expand

This programming challenge is linked to the following lessons:

Challenge 7.3 for How binary digits work (8 to 10)

Learning outcomes

Students will be able to:

Describe how variables store values and how they are used in your program.
Computer Science: Programming
Explain what you need to consider if you are asking for an input from the end user.
Computer Science: Programming
Identify how and when to use a loop to repeat a set of instructions.
Computer Science: Programming
Identify when to use an if statement to check a set of conditions.
Computer Science: Programming

Requirement:

Write a program that asks the user to enter any decimal number as the input and displays the binary cards representing that number using '1' for dots showing and '0' for not showing as the output (this converts the decimal number to binary). Do this by working out the largest bit value needed, and then working down through smaller bit values.

Testing examples:

Your program should display the outputs shown in this table for the given inputs provided:

Input	Output
31	The binary representation for the number 31 is 11111
32	The binary representation for the number 32 is 100000
1	The binary representation for the number 1 is 1

Languages

Scratch

What it should look like

Click on the green flag, enter the inputs provided in the “testing examples” to see the expected output of your program.

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Recommended blocks

Hints

Make variables called:
- “decimal number” and set its value to the input number given by the end user.
- “bit value” and set its value to ‘1’. Find the smallest bit value which is larger than the “decimal number” by doubling value of “bit value” until it is bigger than the “decimal number”.
- “binary number” is a string variable and stores the binary cards needed (‘1’ for dots showing and ‘0’ for not showing).
Set the variable “bit value” to 1 and find the smallest “bit value” which is larger than “decimal number” by multiplying “bit value” by 2 (Use the block under “Operators” to multiply the “bit value” by 2) until it is larger than “decimal number”. You can do this by using a loop.
Now divide the “bit value” by 2 and check if “decimal number” is greater than or equal to “bit value”. If it is, add ‘1’ to string variable “cards” and subtract “bit value” from the “ decimal number”. If not, add ‘0’ to string variable “cards”. Repeat until “bit value” is equal to 1. Display the value of “cards” as the output.

Show Scratch solution

Python

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