Storage Devices
What Storage Does; Primary Storage; Secondary Storage; Comparing Storage Devices; How Data Is Stored and Measured; Types of Secondary Storage
On this page9 sections
- 01Learning Objectives
- 02What Storage Does
- 03Primary Storage
- 04Secondary Storage
- 05Comparing Storage Devices
- 06How Data Is Stored and Measured
- 07Types of Secondary Storage
- 08Practical Work
- 09Scenario-Based Questions
Learning Objectives
- Define storage and state why a computer needs storage.
- Differentiate between primary and secondary storage.
- Name the common secondary storage devices.
- State the units used to measure storage.
What Storage Does
Storage keeps data so that it can be used again later. A computer needs storage for three reasons. Programs must be available when the machine starts. Data must survive after the machine is switched off. Work must be kept while other work is being done.
The amount of storage is measured in bits and bytes. A bit is the smallest unit and holds a single 0 or 1. A byte is made of eight bits and holds one character. Larger units are the kilobyte, megabyte, gigabyte and terabyte.
Primary Storage
Primary storage is the working memory of the computer. It is very fast and is used directly by the processor. RAM is the main part. RAM holds programs and data only while the computer is on, and its contents are lost when the power goes off.
ROM is read only memory. Its contents are fixed when it is made and it cannot be written to by the user. ROM keeps the start up instructions that the computer needs before any operating system loads. Cache is a small fast memory that holds data the processor is about to use.
Secondary Storage
Secondary storage keeps data permanently. It is slower than primary storage but much larger. The hard disk drive stores the operating system, programs and files. A solid state drive does the same job faster because it has no moving parts.
Removable secondary storage includes the flash drive, memory card, optical disc and external hard disk. Optical discs come as CD, DVD and Blu-ray. The flash drive and memory card are now more common because they are small, fast and cheap.
Comparing Storage Devices
Storage devices are compared by capacity, speed, portability and cost. A hard disk has large capacity but is fixed inside the computer. A flash drive has smaller capacity but can be carried. An optical disc can be read easily but has low capacity and can be scratched.
Learners should check free space before saving large files. Deleting a file frees space, but the space is only returned to the system when the Recycle Bin is emptied.
How Data Is Stored and Measured
A computer stores everything in binary, using only the digits 0 and 1. Each 0 or 1 is called a bit, and eight bits make a byte, which can hold one character such as the letter A.
Storage capacity is measured in units that grow larger. A kilobyte is about one thousand bytes, a megabyte is about one million bytes, a gigabyte is about one thousand megabytes, and a terabyte is about one thousand gigabytes.
Types of Secondary Storage
Different storage devices suit different jobs. A hard disk drive uses spinning magnetic discs and gives a large capacity at low cost. A solid state drive uses electronic chips, so it is faster, quieter and more durable. A flash drive and a memory card are small and portable. Optical discs such as CDs and DVDs store data that a laser reads.
| Unit | Approximate size |
|---|---|
| Bit | One single 0 or 1 |
| Byte | 8 bits, one character |
| Kilobyte | 1024 bytes |
| Megabyte | 1024 kilobytes |
| Gigabyte | 1024 megabytes |
| Terabyte | 1024 gigabytes |
| Device | Type | Capacity | Portable |
|---|---|---|---|
| RAM | Primary | Small | No |
| ROM | Primary | Small and fixed | No |
| Cache | Primary | Very small | No |
| Hard disk drive | Secondary | Large | No |
| Solid state drive | Secondary | Large | No |
| Flash drive | Secondary | Medium | Yes |
| Memory card | Secondary | Small | Yes |
| CD and DVD | Secondary | Medium | Yes |
| External hard disk | Secondary | Very large | Yes |
| Unit | Size |
|---|---|
| Bit | A single 0 or 1 |
| Byte | Eight bits, about one character |
| Kilobyte | About one thousand bytes |
| Megabyte | About one million bytes |
| Gigabyte | About one thousand megabytes |
| Terabyte | About one thousand gigabytes |
Practical Work
- Check and write down the total and free space of the laboratory computer hard disk.
- Insert a flash drive, create a folder on it and copy three files into the folder.
- Measure the size of three files of different types and record which type uses the most space.
- Empty the Recycle Bin and record how much free space is regained.
- Compare the speed of opening the same file from the hard disk and from a flash drive.
Scenario-Based Questions
- A pupil needs space to save a large video but the computer reports that there is not enough room. Give two ways to create space.
- Explain why a computer will not start properly if the RAM is faulty.
- A school wants to give each learner 8GB of portable storage. Name the device and state two reasons it is suitable.
- Differentiate between RAM and ROM using a table of four points.
- Explain what is lost and what is kept when a computer is switched off.
- A file of 40MB is copied onto a flash drive that has 25MB free. Explain what happens and why.
- Explain why a solid state drive makes a computer feel faster even when the processor is unchanged.
LEARNING OBJECTIVES: BY THE END OF THE LESSON PUPILS SHOULD BE ABLE TO:
| Cognitive | i. Define storage and state why a computer needs storage. ii. Differentiate between primary and secondary storage. iii. Name the common secondary storage devices. iv. State the units used to measure storage. |
| Affective | i. Appreciate the value of Storage Devices in school, at home and in the community. ii. Show willingness to use digital tools carefully, safely and responsibly. |
| Psychomotor | i. Check and write down the total and free space of the laboratory computer hard disk. ii. Insert a flash drive, create a folder on it and copy three files into the folder. iii. Measure the size of three files of different types and record which type uses the most space. iv. Empty the Recycle Bin and record how much free space is regained. |
Rationale: Storage keeps data so that it can be used again later. Understanding what Storage Does, primary Storage, secondary Storage, comparing Storage Devices helps learners use digital technology confidently, safely and responsibly.
Pre-requisite Knowledge: In Week 6, learners studied Basic Typing Skills, including parts of the Keyboard, finger Position, typing Practice and Accuracy. The knowledge from that week is used again in this lesson.
Learning Material/Teaching Aid: Whiteboard, markers, computer or laptop where available, printed notes and charts on Storage Devices, practical task sheets, learners' notebooks and pens.
Reference Materials: Digital Technology for Junior Secondary Schools (JSS 1); NERDC Digital Technology Curriculum; Digital Technology JSS 1 First Term Notes (Week 7); First Term examination and Continuous Assessment question papers.
LESSON DEVELOPMENT
| Stage/Step (Time) | Teacher's Activities | Student's Activities | Learning Points |
|---|---|---|---|
| Introduction 5 MINUTES | Welcomes learners, revises Week 6 (Basic Typing Skills) with two quick oral questions, and asks what they already know about Storage Devices. Elicits responses and writes the topic on the board. | Recall the previous lesson and share what they already know about Storage Devices. | Connecting prior knowledge to Storage Devices. |
| Step 1 6 MINUTES | Covers What Storage Does: Storage keeps data so that it can be used again later. A computer needs storage for three reasons. Covers Primary Storage: Primary storage is the working memory of the computer. It is very fast and is used directly by the processor. | Listen, take notes and answer oral questions on "What Storage Does" and related points. | Understanding: What Storage Does; Primary Storage. |
| Step 2 6 MINUTES | Covers Secondary Storage: Secondary storage keeps data permanently. It is slower than primary storage but much larger. Covers Comparing Storage Devices: Storage devices are compared by capacity, speed, portability and cost. A hard disk has large capacity but is fixed inside the computer. | Copy the key points, give examples from school and everyday life, and ask questions on "Secondary Storage" and related points. | Understanding: Secondary Storage; Comparing Storage Devices. |
| Step 3 6 MINUTES | Covers How Data Is Stored and Measured: A computer stores everything in binary, using only the digits 0 and 1. Each 0 or 1 is called a bit, and eight bits make a byte, which can hold one character such as the letter A. | Discuss in pairs, then report one point on "How Data Is Stored and Measured" to the class. | Understanding: How Data Is Stored and Measured. |
| Step 4 6 MINUTES | Covers Types of Secondary Storage: Different storage devices suit different jobs. A hard disk drive uses spinning magnetic discs and gives a large capacity at low cost. A solid state drive uses electronic chips, so it is faster, quieter and more durable. | Respond to questions, complete the examples on the board and note down "Types of Secondary Storage". | Understanding: Types of Secondary Storage. |
| Practical Work 6 MINUTES | Guides learners through the practical work: (i) Check and write down the total and free space of the laboratory computer hard disk. (ii) Insert a flash drive, create a folder on it and copy three files into the folder. (iii) Measure the size of three files of different types and record which type uses the most space. Moves round the class to check progress and correct unsafe or careless use. | Carry out the practical tasks individually or in pairs and record what they did in their notebooks. | Applying the lesson through hands-on practice. |
| Evaluation 3 MINUTES | Asks learners to: i. Define storage and state why a computer needs storage. ii. Differentiate between primary and secondary storage. iii. Name the common secondary storage devices. iv. State the units used to measure storage. | Respond verbally and in writing to the evaluation questions. | Assessment and consolidation of the lesson content. |
| Conclusion 2 MINUTES | Recaps the main points: what Storage Does, primary Storage, secondary Storage, comparing Storage Devices, how Data Is Stored and Measured. Links them to the assignment and previews Week 8: Simple Uses of the Internet. | Listen, ask questions and copy the assignment. | Reinforcement of key concepts and a preview of the next lesson. |
Assignment: i. A pupil needs space to save a large video but the computer reports that there is not enough room. Give two ways to create space. ii. Explain why a computer will not start properly if the RAM is faulty.
On this page9 sections
- 01Lesson objectives
- 02Key vocabulary
- 03Common misconceptions
- 04Teacher activities
- 05Student activities
- 06Practical / learning evidence
- 07Resources and preparation
- 08Assessment for learning
- 09Inclusion and homework
Lesson objectives
By the end of the week, learners should be able to:
- Distinguish memory from storage and give one example of each.
- Explain why RAM is volatile and ROM is non-volatile.
- Convert between bytes, kilobytes, megabytes, gigabytes and terabytes using 1024.
- Classify storage devices as magnetic, optical or solid state, with an example of each.
- Compare storage media on capacity, speed, portability and cost.
- State three rules for safe use of a flash drive and one reason for keeping a backup.
Key vocabulary
- Memory: the working area that holds programs and data currently in use, such as RAM.
- Storage: the long-term place where files are kept when the computer is switched off.
- Volatile: loses its contents when power is removed, as RAM does.
- Non-volatile: keeps its contents without power, as ROM, a hard disk or a flash drive does.
- Byte: eight bits, the basic unit of storage.
- Magnetic storage: stores data as magnetised areas, such as a hard disk drive or magnetic tape.
- Optical storage: read by laser, such as a CD, DVD or Blu-ray disc.
- Solid-state storage: stores data in flash memory with no moving parts, such as an SSD, flash drive or memory card.
- Backup: a second copy of files kept in case the original is lost or damaged.
Common misconceptions
- "Memory and storage are the same." RAM is temporary working space. Storage keeps files when the power is off.
- "Deleting a file removes it completely." It usually goes to the Recycle Bin first and can be restored.
- "Cloud storage means the file is not on any device." It is stored on someone else's server and needs a connection to reach.
Teacher activities
- Starter: ask learners where a phone photograph goes when the phone is switched off, and collect three different answers.
- Draw the memory and storage distinction, with RAM, ROM and secondary storage in the correct places.
- Build the unit sequence on the board: bit, byte, KB, MB, GB, TB, and work two conversions with the class.
- Pass round a hard disk, a CD, a flash drive and a memory card. Name each type and its technology.
- Model a capacity comparison: how many 4 MB photographs fit on a 2 GB card, and how many 700 MB CDs equal one 4.7 GB DVD.
- Close with the safe-use rules and a class discussion of the reasons for keeping a backup.
Student activities
- Answer the starter in one sentence before discussion.
- Copy the memory and storage diagram and add two examples to each side.
- Complete five unit conversions, showing the working.
- Identify each device passed round and write its storage type.
- Solve the two capacity problems with a partner and compare methods.
- Write three flash-drive safety rules and one sentence on the value of a backup.
Practical / learning evidence
A conversion worksheet with at least five worked conversions, a three-row storage-type table (magnetic, optical, solid state) with an example and a typical capacity for each, and the two worked capacity problems with the method shown.
Resources and preparation
A hard disk drive, a CD or DVD, a flash drive, a memory card and, if available, an SSD. A short video or demonstration of a CD being read. Calculators for the conversion work. Printed conversion worksheets. Offline route: physical media and worksheets. No computer is required. Warn learners not to insert unknown flash drives into laboratory machines.
Assessment for learning
Mark the working as well as the final answer. A correct answer from a wrong method will fail later questions. Check that RAM is placed under memory, since RAM is working memory. Ask two learners to explain their capacity method aloud before collection.
Inclusion and homework
Allow a printed conversion ladder as a reference for learners who need it, and reduce the worksheet to three items where time is short. Extend confident learners with a comparison of an SSD and a hard disk for a school that needs speed. Homework: find out the storage capacity of any phone, memory card or computer you can access and write it in gigabytes.