☰ Contents · Computing

Working with a computer’s external memory

Lessons 13–14 · 2 lessons · B. Boltayev, A. Azamatov, A. Asqarov, M. Sodiqov, G. Azamatova. Fundamentals of Informatics and Computer Technology, Grade 8. Second edition. “O‘zbekiston milliy ensiklopediyasi” State Scientific Publishing House, Tashkent, 2015
13

Working with a computer’s external memory

Textbook: pp. 61–66
GoalKnows the basic operations with external memory (formatting, writing, reading, deleting, safe removal) and disk services.
New words
formatting: preparing a drive by creating a file system; it erases the data · formatlashsafe eject: telling the OS to finish writing before you remove a drive · xavfsiz chiqarishlogical drive (partition): a part of a physical disk shown as a separate drive, e.g. C: or D: · mantiqiy diskdefragmentation: gathering the scattered pieces of files on an HDD into continuous areas · defragmentatsiya
Explanation

Basic operations with external memory (hard disk, SSD, flash drive, memory card, optical disc) are formatting, writing (copying), reading and deleting. Formatting creates a file system on the disk and erases all its data, so first copy the files you need and format only your own (or permitted) drive. A flash drive plugs into a USB port; before pulling it out choose “Safely remove hardware” (Eject) on the taskbar and wait for the message, otherwise files may be damaged. USB 2.0 gives a theoretical 480 Mbit/s and USB 3.0 gives 5 Gbit/s; since 8 bits = 1 byte, 480 Mbit/s = 60 MB/s. One physical disk can be divided into several logical drives (C:, D:). A CD-R can be written once, a CD-RW many times. With time the files on an HDD break into pieces scattered over the disk (fragmentation) and work slows down; the “Optimize Drives” service gathers them. An SSD does not need defragmenting: it gives no benefit and the OS optimises it by itself. Keep a backup of important data on another device or in cloud storage, and scan a flash drive with antivirus.

Worked examples
Speed: 800 Mbit/s = 800 : 8 = 100 MB/s. A 600 MB file could in ideal conditions be copied in 600 : 100 = 6 seconds (in practice slower).
Partitioning: if a 500 GB disk is split into C: (200 GB) and D:, D: gets 500 – 200 = 300 GB.
Class activity

“Safe removal” script: pairs describe in order, without pictures, the steps of plugging in a flash drive, copying a file and safely removing it; the class finds any mistake.

Practice
1
What must be done before formatting, and why?
2
How many MB/s is 320 Mbit/s?
3
Why is defragmenting useful for an HDD but unnecessary for an SSD?
4
What is the risk of pulling out a flash drive without safe removal?