hi welcome back uh so far we have gone through the IGCSE ICT subject as the introductory video and then we had the first lesson on digital devices and the second lesson was on peripheral input devices uh the third lesson was some physical output devices and today we are going to go through the lesson 4 which is on peripheral storage devices so with this lesson we conclude the chapter one uh of IGCSE ICT subject if you haven't followed the previous lessons go to igcsc ICT playlist and you can follow the previous lessons in the correct order there are some practice questions at the end of the lesson so let's start the lesson I hope you remember this screen from our previous lessons we have completed the input and output devices the first Circle and the second Circle and this lesson is based on third category which is storage devices okay uh this is sort of a classification uh of Memorial storage and I have seen students confuse between memory and storage and they use the words in the wrong manner so let's see memory is what your computer uses to store data temporarily while storage is where you save files permanently when you save a file it's copied from the memory onto the storage Drive another example is if you if we take a mobile phone storage is where you keep your data like music and photos and videos and memories where you run your apps and programs and also the mobile phone operating system in the screen the blue color site is primary memory and that is the memory that we use when we start a computer like when when it's booting the OS and starting software programs and Etc and in this lesson our focus is on the storage devices that is marked in light green color which is in the right side of the screen so secondary memory is permanent memory and non-volatile meaning the data we save will be there even when we switch off the device so under secondary memory we learn on hard disk SSD CD DVD durray Magnetic Tape flash memory so we are we will learn on this in detail so why we need secondary in the first place it's sort of it's pretty obvious right secondary memory is a permanent or non-volatile memory so we used to store our data and retrieve that data and uh we also store our applications absence after in the secondary memory which will be loaded to Ram when the user open the application and secondary memory is also used as virtual memory uh if we look at what virtual memories virtual memory is the space allocated in a computer to store programs and instructions until they are needed or been used uh and then thanks to the storage uh secondary storage devices we can back up our large volumes of data such as photos songs movies and fires and Etc [Music] so those are the uses of the secondary storage uh this is also another misused words by the students and this is also specifically mentioned in the previous exams examiner reports as well so let's see the difference between the storage devices and the storage media let's take some examples so that you will understand clearly the device that actually holds the data is known as the storage media the device that saves data onto the storage media or reads data from it is known as the storage device sometimes the storage media is fixed or permanent part of the storage devices for an example the magnetic coated disk built into a hard drive sometimes the storage media is removable from the device example A CD-ROM can be taken out of a CD drive uh flash memory is the media used to store data whereas USB drive is used to contain the flash media so that it can be read by the computer after it is plugged into a USB port so those are some examples that you can see the difference between the CD-ROM and the CD drive what is the storage device and what is the storage media right for IGCSE level uh these are this is a screen of units of storage capacity and for IGCSE level you only need to know the first four rows you don't need to remember the dark red rows the last four rows so data storage capacity is measured in bytes uh in we don't denote it with the letter B so if you can if you look at the first row uh four rows 1000 bytes is known as kilobyte one kilobyte so 1000 D equals 1 KB and then a million bytes is known as a megabyte we write it as one him B uh a thousand million byte is called gigabyte and we write it as GB 1 GB [Music] and then we need to discuss about the data access speed uh some storage devices can access data very quickly While others are like extremely slow access speeds are measured in bytes per second uh we call it as Mbps uh slow devices have speeds measured in like thousands of uh VPS so we call it we normally tell kbps kilobytes per second uh examples are like floppy disk can see save or read data at a speed of 60 kbps meaning uh properties can save data or read data 60 kilo bytes per second fast devices have speeds measured in millions of BPS like via Mbps so for an example a hard drive can read or save data at a speed of 300 Mbps meaning it can save or read data 300 megabytes per second so that is like uh around 5000 times quicker than a profit disk okay now let's see the types of secondary storage secondary storage cannot be accessed directly by the CPU secondary memory is non-volatile and used to store data permanently so even if you switch off the data is sale there and they are relatively cheap compared to the primary storage and because of that we can have a larger secondary storage devices secondary storage devices can be classified into three main types magnetic storage devices optical storage devices and solid state storage devices magnetic storage devices use magnetized fields on spinning metal disk to locate store the information and data examples are hard disk drives and magnetic tapes optical storage devices use lasers and microscopic light on a grooved plastic or metal disc to locate stored information and data so that's why it's since it's use a laser that's why we call it as optical storage and for examples are CD DVDs and Blu-ray disc the third category solid state storage devices make use of silicon microchips with transistors and an electrical current to determine the location of stored data and examples for these uh USB or the flash drive and memory chips uh the SSD cards a secondary storage devices can be classified into three types uh as we discussed in the previous screen magnetic storage devices use magnetized fields on a spinning metal disk to locate the stored information data and the optical storage devices used lasers and microscopic light on a group the plastic commentary list to locate stored stored information and solid state storage devices make sure make use of silicon microchips with transistors and an electrical current to determine the location of the stored data so you can see uh secondary storage devices we have magnetic disk Optical disk and memory storage devices and on the magnet magnetic disk we have floppy disk hard disk and Optical disk we have CD-ROM CD DVD and Blu-rays and on the memory storage the solid state we have flash flash drives and memory cards okay the most common storage device is the hard disk drive and hard drives have a very large storage capacity like terabytes and they can be used to store vast amount of data like hard drives are like random access devices and can be used to store all types of films including huge files such as yeah films movies and all that and this data access speeds are very fast let's see the structure of a disk we see the diagram on the screen a hard disk contains a stack of platters a circular metal disk that are mounted inside the hard disk drive and coated with Magnetic material sealed in a material case or unit and uh if you can see you can see the platters uh let me see you can see a stack of practice right in in the needle and and they are mounted inside the hard disk drive and they are coated with Magnetic material and normally this is a covered closed unit to protect from the dust and all that hard disk has a electromagnetic read or right heads above and below the platters uh you can see on top of on the screen top of the screen there's a read write hit pointing label pointing it to the free dried head and it's on top of the platters all the platters make up a cylinder so all together when you look at all the platters it sort of create a cylinder that spins on a central spindle look at the diagram you can find the spindle there so that Celine platters that makes a cylinder spins on a central spindle as I mentioned uh this is sort of covered and sealed because even a smoke particle or a dust particle can cause issues in a hard disk because the gap between the platter and the red right head is only few nanometers look at the diagram so you can see a set of platters and top of that you can see the uh read write head and the distance between these platters and these straight right head is just few nanometers so even a small uh small particle or a dust particle can cause issues in the hard disk so that's why to prevent this uh hard drives use filters or it it either it's sealed or they use filters to prevent this issue same as hard disk magnetic tips also allow to store large volumes of data but retrieving data from Magnetic Tape is very slow which is a disadvantage of using magnetic tapes okay now we are going to the second type Optical media devices data written method then is different in these three types like we magnetic tapes and Optical media so there's a difference and due to that difference the storage capacity also changes in the optical media like if we take the CDs CDs data is written used in laser and can store up to about 700 MBS uh and if we take DVDs data state news in red laser light and because of that it allows to store more data uh up to 7gb in single side and can go up to 818 GB both sides and if it uh check door Blu-ray writes data using Violet laser light you remember right in CDs we are using a laser and in DVDs by using red lace light and Blu-ray we are using Violet laser light and it allows to store data densely because of the Violet laser and can store up to 25 GB in single side and can go up to 50 GB double side that's how the name derived as Blu-ray ideally it should be Violet Ray but they thought blue Rays more trendier because of that they started calling it Blu-ray [Music] the third category of the storage device device type that we discussed was solid state storage devices the term solid state essentially means no moving parts uh solid state storage devices are based on electronic circuits with no moving Parts uh like in the hard disk we have the spindle and the tapes we are reels of tape and no laser beams so nothing so that's why we call this solid state storage devices and no moving Parts solid state storage devices store data use in a special type of memory code flash memory and first type is your USB memory sticks memory sticks or thumb drivers have made any many other forms of portable storage almost obsolete like why you want to burn a CD or a DVD when you can more easily copy your files onto a memory stick right in the pre early days when we didn't have this people used to copy the data using a software into the rcg so DVDs and it was a hassle sometimes you cannot rewrite to the CD and then you have to throw away those so now but now you have the USB memory sticks where you can just uh plug into the USB port and copy your files and also you can rewrite and delete and create add new more files likewise then we have memory cards uh the second type there are many varieties many of our digital devices like cameras mobile phones uh MP3 players and extra Etc they are using these memory cards because they want more uh compact storage devices so these memory cards are very Compact and they can insert into their mobile phones and cameras in p3ps and Etc one of the most common formats used by digital cameras is the SD card the cards to the digital images taken by the camera and mobile phones contain a subscriber identity module we call it as a Sim in chart and that Sim contains the phone's numbers the phone book text messages and Etc and many phones also have extra memory cards to store the music video photos and Etc and sometimes we call it as a tiny micro SD cards then we have Smart cards uh many uh credit cards uh example chip pen pin cards dough entry cards uh satellite TV cards Etc have replaced a very limited storage of the magnetic strip uh the dark strip on the back of all the card uh with flash memory and this is more reliable and uh has a much larger storage capacity as well cars with flash memory are called smart cards okay so now I guess you have learned many real life examples of solid storage devices and we are using it in your day-to-day life as well so uh next we will move okay here's a comparison of storage device types which you can read yourself uh for an example now here here we are com uh comparing hard disk flash media Optical media and Magnetic Tape uh as we know the flash media is the fastest uh day when we are accessing the data and Magnetic Tape is the slowest we mentioned that as the disadvantages of using magnetic tape and then capacity wise uh hard disk can go up to more than the screen shows one to eight GB but they are a hard disk nowadays bigger than this and we discuss about the optical media the CD can go up to 700 and in the DVD could go up to 18 GB and Blu-ray could go up to 50 GB and the usage wise hard disk we're using inside the service the personal computers and the Flash media is used in laptops and mobile devices and Optical media more or less are used in multimedia like music CDs games and films and we are also using to backup our data and for portability the hard disk is not suitable because it's sort of fixed and Flash media it's really portable we can take it anywhere and Optical media it's uh portability is possible but when you are uh when it's portable it could damage the optical media yeah so you can read this one and let's go through some of the simple questions that based on this lesson uh first question give two users of secondary storage yeah secondary storage we discussed Four Points uh we can store large amounts of data we can store software applications and we can backup our large volumes of important data and files and also a secondary storage acts as a virtual memory so those are the four points that we discussed uh give three types of secondary storage devices we discussed three types uh magnetic storage devices Optical and then uh Flash pen drives this is these micro SDs those stuff third one what are the rough uh storage capacities of the following are disk CD dividend Blu-ray okay a hard disk drive it can go up to like nowadays it's uh around one terabyte and see this it's about 700 MB DVDs uh it's one side 4.7 GB and Blu-ray it's a single size it's 25 GB and both sides it could go up to 50 GB next question right two advantages of flash storage yeah it's solid state so uh because of that it can handle shocks and drops and Flash member storage is durable and this read and write speeds are faster and it's a compact uh and because of that it's easy to uh its portability is high okay the next next question right one advantages of magnetic tape uh Magnetic Tape advantages it's a its provides a huge storage capacity so when we are backing up large amounts of data when we are backing up on daily a lot of transactions uh Magnetic Tape is ideal but the disadvantages if they ask is it's very slow okay this question I got from 2020 exam paper the laptop can store uh 100 okay read the question again the laptop can store 128 GB of uh data construct an expression to show how many bits are in 128 game so we learn 1 GB is 1024 MB and 1 MB is 1024 KB and 1 KB is 1024 bytes so 1 byte has uh eight bits so they want uh the expression in bits how many bits so uh now we need to do the conversion into the expression so number of bits equals uh the amount given is 128 ideally this should be 128 and multiplied by 1024 to convert it to MB and then again multiply by 1024 to convert it to KB and again Tau uh multiply by 1024 to make it uh KB and uh again multiplied by 8 to convert the bytes into bits you don't need to uh get a final answer just put in the construct uh is enough to get the full marks and I I have put 1GB uh the the first four lines you don't have to write in the exam just put in the construct is enough I have just I have mentioned those for your understanding right this is from 2016 June exam paper uh access to computer room is controlled by biometric scanners identify one biometric that can be scanned okay this we discussed in the previous lesson uh we can any any answer like fingerprint or thumbprint it could be a retinal scan or face recognition or Voice or speech recognition you can mention any of these to get one mark the second one give one benefit of using a biometric scanner to gain access to the roles we discussed many uh advantages and you need to write one uh in the in the previous one I I have to tell you uh in the first one I identify one biometric that can be scanned they gave marks for a fingerprint thumbprint and everything but they didn't give marks for finger instead of fingerprint so identify one biometric that can be scanned if you write just finger then you won't get marks it has to be fingerprint okay right okay we'll go back again to the second one uh give one benefit of using a biometric scanner to gain access to the rules uh yeah it there are many benefits like you don't need to need the users to carry their ID or they don't have to remember a password or anything so that's a benefit and uh because the person has to present himself others cannot misused or store steel or guest or anything so that that's a safety measure is there uh yeah you can write any any of these and then third one give one possible drawback of using a biometric scanner to gain access to the rooms okay uh let's say a fingerprint uh sometimes uh the way you put your finger sometimes it might not work and uh so the scanner might not read it correctly and there could be system failures so when when there's a system period there's no way that you can get access and let's say there could be an injury happened uh a temporary injury let's say your finger got some injured and now there's no way that you can uh access so those are few uh drawbacks of using biometric scanners okay so with this we conclude the lesson on storage devices and we are now done with IGCSE ICT chapter one so next lesson will be on uh chapter two a new chapter so until next lesson goodbye and good luck with your studies