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CAIE 9618 · Paper 1 · Topic 1.3.4

Input, Output &
Storage Devices

HDD · SSD · Optical · Magnetic Tape · I/O Device Selection

CSZone Cambridge International AS & A Level Computer Science 9618
Input Devices

Getting Data Into the Computer

Keyboard — text/command input; sends ASCII/Unicode codes
Mouse / touchpad — pointer/GUI control; optical or laser sensor
Touchscreen — capacitive or resistive; combines input and output
Barcode scanner — reads product codes; laser reflected off bars
QR code reader — 2D matrix code; more data than barcode
RFID reader — radio frequency identification; passive tags (no battery)
Biometric scanner — fingerprint, iris, face recognition; unique to each person
Microphone — captures sound; ADC converts analogue to digital
Digital camera / webcam — captures images/video; CCD/CMOS sensor
Output Devices

Getting Data Out of the Computer

Monitor/screen — LCD, OLED, TFT; pixels controlled by GPU
Printer (inkjet) — droplets of ink; good colour, high detail, slow
Printer (laser) — toner + drum + fuser; fast, cheap per page
3D printer — additive manufacturing; builds objects layer by layer
Speakers/headphones — DAC converts digital to analogue; audio output
Actuators — convert digital signal into physical action (motors, valves) — used in control systems
Projector — displays computer image on large screen; DLP or LCD based
Secondary Storage — Magnetic

HDD & Magnetic Tape

HDD — HARD DISK DRIVE
Spinning magnetic platters read/written by read/write heads. Random access. Capacity: TBs. Speed: ~150 MB/s. Mechanical — prone to physical shock damage. Cheap per GB.
MAGNETIC TAPE
Sequential access only — must read through tape to reach data. Very high capacity (many TBs). Slowest access. Cheapest per GB. Used for long-term archival and backup.
Secondary Storage — SSD & Optical

Flash Memory & Optical Discs

SSD — SOLID STATE DRIVE
NAND flash memory — no moving parts. Fast (600+ MB/s SATA, 7000+ MB/s NVMe). Silent, low power, shock resistant. More expensive per GB than HDD. Writes limited (endurance).
OPTICAL — CD / DVD / BLU-RAY
Data stored as pits/lands read by laser. CD ≈ 700 MB. DVD ≈ 4.7 GB. Blu-ray ≈ 25 GB. Portable and durable. Read-only (ROM) or writable (R/RW). Slower access than HDD/SSD.
Storage Comparison

Choosing the Right Storage

TypeAccessSpeedCapacityCost/GBBest Use
HDDRandomMediumTB+LowMass storage, servers
SSDRandomVery fastTBHighOS, apps, speed-critical
OpticalSequentialSlow25 GBVery lowDistribution, archiving
TapeSequentialVery slow100s TBLowestLong-term backups
USB/FlashRandomFast256 GB+MediumPortable transfer
Exam Practice

Cambridge-style questions

Question 1
A hospital needs to back up 50 TB of patient records monthly. The data is rarely accessed but must be kept for 25 years. Recommend a suitable storage medium. Justify your answer.
4 marks
1 mark
Magnetic tape is the recommended storage medium
1 mark
Very high capacity — can store hundreds of TB per cartridge, suitable for 50 TB backup
1 mark
Cheapest cost per GB — cost-effective for long-term storage of large amounts of infrequently accessed data
1 mark
Physically durable and long-lasting — suitable for 25-year archival (slow access acceptable as data is rarely retrieved)
Common Mistakes

Don't lose easy marks

1
Saying SSD is always better than HDD — SSD is faster and more durable but costs more per GB. For mass storage (e.g. backup of many TBs at low cost), HDD remains more appropriate. Always consider the context.
2
Describing magnetic tape as unreliable — magnetic tape is actually extremely reliable for long-term archival storage. Its main disadvantage is sequential access (slow to retrieve specific data), not reliability.
3
Saying RAM is a type of secondary storage — RAM is primary (main) storage. Secondary storage is persistent (HDD, SSD, optical, tape). RAM is volatile — it loses its contents when power is removed.
Topic Summary — 1.3.4

What You Need to Know

INPUT DEVICES
Keyboard, mouse, scanner, RFID, biometric
Microphone: ADC converts analogue → digital
Camera: CCD/CMOS sensor
Barcode: laser reflection · QR: 2D matrix
OUTPUT DEVICES
Monitor: LCD/OLED pixels
Printer: inkjet (colour), laser (fast/cheap)
Speaker: DAC digital → analogue
Actuator: digital → physical movement
SECONDARY STORAGE
HDD: spinning, random access, cheap, TB+
SSD: flash, fast, no moving parts, pricier
Optical: laser, pits/lands, portable, limited
Tape: sequential only, cheapest, archival
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1.3.5
Memory Types
RAM · ROM · Cache · Registers · Memory Hierarchy
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