Lec 3- Storage and Memory (BCS101) - Fall 2024/2025 PDF

BCS101- Computer Science Fundamentals Fall 2024 / 2025 Lec 3: Storage and Memory Dr. Esraa Mosleh  Agenda Digital vs Analog Memory vs. Storage ❖ Primary Storage ❖ Secondary Storage Machine cycle 2 Digital vs Analog...

BCS101- Computer Science Fundamentals Fall 2024 / 2025 Lec 3: Storage and Memory Dr. Esraa Mosleh  Agenda Digital vs Analog Memory vs. Storage ❖ Primary Storage ❖ Secondary Storage Machine cycle 2 Digital vs Analog 3 Digital vs Analog (cont.) 4 Digital vs Analog (cont.) 5 Digital vs Analog (cont.) 6 Digital vs Analog (cont.) 7 Digital vs Analog (cont.) 8 Digital vs Analog (cont.) 9 Digital vs Analog (cont.) 10 Digital vs Analog (cont.) 11 Digital vs Analog (cont.) 12 Digital vs Analog (cont.) 13 Digital vs Analog (cont.) 14 Digital vs Analog (cont.) 15  Memory vs. Storage Hard Drive RAM Memory Storage, also known as mass media or auxiliary storage, refers to the various media on which a computer system can store data. Storage devices hold programs and data in units called files. Files are stored in directories or folders. Memory refers to a temporary (sometimes permanent) workplace where the computer transfers the contents of a file while it is being used. 16 Memory vs. Storage 17 Primary Storage (Memory) 18 Primary Storage (ROM) 19 Primary Storage (RAM) 20 Secondary Storage 21 Secondary Storage (Hard Disk) 22  Secondary Storage (Hard Disk) (cont.) Platter Read/Write head Hard disks are a high-speed, high-capacity storage devices. They contain metal disks called platters. They contain two or more stacked platters with read/write heads for each side. Hard disks can be divided into partitions to enable computers to work with more than one operating system. 23  Secondary Storage (Hard Disk) (cont.) Factors Affecting a Hard Disk’s Performance: Seek time or positioning performance: How quickly the read/write head positions itself and begins transferring information. It is measured in milliseconds (ms). Spindle speed or transfer performance: How quickly the drive transfers data. It is measured in rotations per minute (RPM). Latency: The time it takes for the spinning platter to bring the desired data to the read/write head. It is measured in milliseconds (ms). 24  Secondary Storage (CD-ROM Disks and Drives) CD-ROM stands for Compact Disk-Read Only Memory. They are capable of storing 650 MB of data. They are used for storing operating systems, large application programs, and multimedia programs. 25  Secondary Storage (CD-ROM Disks and Drives) CD-R and CD-RW Disks and Recorders CD-R CD-RW Disks that can be read and written Disks that can be read and written to them. to them. Disks can only be written to “once”. Disks are erasable. Drives that are capable of reading Disks can be written to them many and writing data are needed. times. Drives that are capable of reading, writing and erasing data are needed. 26 Secondary Storage (DVD-RAM Disks and Drives) DVD stands for Digital Video Disk. They use technology similar to CD-ROM. They are capable of storing up to 17GB of data. Their data transfer rate is comparable to that of hard disk drives. DVD-RAM– Has the ability to read/write data. 27 Secondary Storage (Floppy Disks and Disk Drives) A disk or diskette is a portable storage medium. Disks are circular plastic disks coated with a magnetically sensitive film. Disks work with a disk drive. Floppy disks store 1.44 MB of data. SuperDisk and High FD disks store up to 250 MB of data and are downwardly compatible with floppy disks 28 Secondary Storage (Floppy Disks and Disk Drives) Disk Organization Track A disk is formatted–that is, it is divided into tracks and sectors and a File Sector Allocation Table (FAT) is created. Track: circular band Sector: pie shaped section Cluster Cluster: two or more adjacent sectors FAT: keeps track of specific locations of files 29 Secondary Storage (USB Flash) 30 Secondary Storage (Memory Cards) 31 Capacity and Speed of Storage Devices Floppy Disk Hard Drive CD ROM / DVD Capacity– 720 KB to 1.44 MB Capacity– Up to 1 TB Capacity– CD-ROM 650 MB; DVD 17 GB Access Time– 100ms Access Time– 6 to 12ms Access Time– 80 to 800ms A storage device’s performance is measured by: Capacity: The number of bytes of data that a device can hold. Access Time: The amount of time, in milliseconds (ms), it takes for the device to begin reading data. 32  Secondary Storage Secondary Storage devices are: Hardware that is capable of retaining data when the electricity is turned off. Able to read (retrieve) data from a storage medium (disk/tape). Able to write (record) data to a storage medium. 33  Why is Storage Necessary? It Retains data when the computer is turned off. Plays an important role during startup. Plays an input role when starting applications. Is needed for output. Devices can hold a large amount of data. 34  Types of Storage Technologies Sequential: Hardware that reads and writes data in a serial (one after the other) fashion. Random-Access: Hardware that reads and writes data without going through a sequence of locations. Magnetic: Hardware that uses disks or tapes that are coated with magnetic material. Optical: Hardware that uses laser beams to read data from plastic disks. Solid State: Devices that use nonvolatile memory chips to read and write data. 35  Machine cycle Machine cycle: the amount of time needed to execute an instruction There are four steps performed for each instruction Personal computers execute in less than one millionth of a second Supercomputers execute in less than one trillionth of a second Each CPU has its own instruction set those instructions that CPU can understand and execute 36  Machine cycle (cont.) CPU Consists of: Machine cycle (cont.) 38 Thanks for your kind listening