Chapter 3 – Computer Hardware Computer Components – Hardware (cont.) Lecture 3

Outline  Computer Components  Hardware Components  Central Processing Unit  Input Units  Output Units  Memory Unit  Storage Units 2

Computer Components  Computers have two main components:  Hardware Physical components like screen and keyboard  Software Set of instructions that tells the computer what to do and how to do it 3

Hardware Components  Central Processing Unit  Input Units  Output Units  Memory Unit  Storage Units 4

Memory Unit Kinds of Memory Primary Memory Secondary Memory

1- Primary Memory Forms of Primary Memory ROM Cash Memory Flash Memory RAM

1- RAM (Random Access Memory)  Main memory in a computer.  It work when the computer is run, all software must holds from the hard drive to the main memory to work on it.  All the user work are stored in this memory until saved it on the hard disk or another storage device.  RAM is volatile, means the data will be lost once the computer shuts down, So it is recommended to save work first by first.  RAM is measured in Megabytes(MB) and memory speed measured in Megahertz(MHz).

2- ROM (Read Only Memory)  It is very small capacity and keeps instructions which make the computer work.  It is not volatile.  The computer cannot write on it or use it.

3- Cache memory  It is linked to the CPU.  It is very fast.  Keeps the data and programs that are used a lot so to decrease the calling time from the main memory and increase speed of the computer.  These days the capacity reach to KB.

Memory 4- Flash  It is not volatile like ROM.  The data are stored into blocks, so it saves and erased data in fast way.  Used to save BIOS in the computer.  It can be used in Mobiles, Portables, digital camera and printers.

Power Cuts If there is a power cut while the computer is On: 1- Unsaved information will be lost. 2- Some files or programs may be corrupted.  When you open the device again after return the electricity implemented program is check the hard drive automatically to news about the mistakes and failures the action.

To decrease the damaged when the power cuts, do the following: 1- Turn off the computer and unplugged. 2- Use Surge protectors. 3- Use an Uninterrupted Power Supply(UPS) that will keep the computer running for a little period to save your work and shut down your computer.

Representing Data in the Computer  Main memory similar human memory and secondary memory like WordPad or the book, both to remember certain information but operate in a special way.  The data are stored in the computer by using binary system (symbols 0.1).  Off = 0, On=1  Each of these symbols are named (bit), bit is shortcut for Binary Digits.  Each 8-bit called (Byte) (8 bits = 1 byte).  Byte is the number of binary units that required to represent a single code in a computer.  Memory capacity are measured by Megabyte. Bits per seconds(bps)  Transmission rate of data from and to memory are measured by the number of bits per second Bits per seconds(bps)

Bit1,0 Byte 8 Bit (one character) Kilo Byte 1024 Byte= 2 10 Byte Mega Byte 1024 Kilo Byte= 2 20 Byte Giga Byte 1024 Mega Byte= 2 30 Byte Tera Byte 1024 Giga Byte= 2 40 Byte Memory Capacity Measurement

Terabyte Gigabyte Megabyte Kilobyte Byte Bit 1024× 8×8× 1024÷ 8÷8÷

Exercise We have a memory of a computer store bytes of data What is the size of the data of KB unit? If one of KB = 1024 bytes The bytes ÷ 1024 = 2048 KB

Memory Chips  RAM is manufactured on Chips.  Chips are assembled on small cards that can be inserted into slots of the motherboard.  Each card has a storage capacity ( ) MB.  You can adding extra memory to the computer to upgrade your computer.

Secondary Storage  Used to store software and data files permanently before shutting down your computer.  Slower than the main memory.  It has different types and each have special drive, you must put it before use.

Hardware Components Input Units Output Units 19 Control Unit Storage Unit ALU Unit

Hardware Components Input Units Output Units 20 Control Unit Storage Unit ALU Unit

Storage Unit Internal Unit External Unit 21

Internal Storage Device 1- Hard Disk:  The most important storage media because it is very fast and high capacity (Gigabyte)  Located inside the system unit.  It is composed of several magnetic disks in a signal unit.  Extra hard disk can be added externally or internally.

External Storage Device  Floppy Disk  Optical Disk  USB Flash Drive  External Hard Desk 23

1- Floppy Disk:  It is a magnetic disk in plastic case.  It is small and portable.  Inexpensive.  It has 1.4 MB capacity.  It is used to transfer files from one computer to another.  Slower than the hard disk. External Storage Device

2- CD-ROM (Compact Disk - Read Only Memory)  Uses laser to read information.  It can store large amount of data up to 750MB  Used to store multimedia software.  Slower than the hard disk.  The computer must be has a special drive to read or write this disk. There are tow basic types of CDs: 1- CD-R (Recordable): can be written to once, and can be read many times. 2- CD-RW (Rewritable): can change, erase and add more data. External Storage Device

3- DVD (Digital Versatile Disk):  Uses optical discs technique.  High capacity measured in Gigabytes.  Used to store high quality films and video.  It can store large amount of data between 4.7 to 17 GB. 4- Zip Disc:  Similar to floppy disks but bigger.  It can store large amount of data ( MB) 5- USB flash drive:  Small and can be placed into pocket.  Used to save and transmit large multimedia files.  To use it, connecting to a USB port. External Storage Device

6- Magnetic Tape:  It is made of flexible plastic coated on one side with magnetic material.  Used to mainly provide duplicate storage as a backup. 7- Smart Card:  Looks like credit card.  Contain a microprocessor and memory chip.  Ex. Telephone Cards. External Storage Device

Stored Data  Storage devices are important because they are stored the data away of the main memory.  A Set of characters makes a Field.  A Set of fields makes a Record.  A Set of records makes a File.  Files are stored in a Directory.  Each files have a name (chosen by the user) and extension (selected by the program)

There are a lot of operations that can be made on files: 1- Creating, naming and saving file. 2- Copying, moving and deleting file. 3- Retrieving information. 4- Displaying, updating and printing file. 5- Uploading and downloading file. 6- Exporting and importing file. 7- Compressing and protecting file.

Computer Performance Computer Performance: Factors that affect the speed of CPU processing: 1- Clock Speed: the faster clock speed increased the instructions that will be executed per second and so increase the speed of the computer 2- Main Memory Capacity: If the amount of your work is greater than the memory capacity, the computer will be use a part of a hard disk, but it is slower than the main memory. 3- Hard Disk Speed: the access speed of data and software will affect computer performance.

Computer Performance 4- Bus Speed: is an electrical pathway which carries the data and commands between the parts of the computer.  Address Bus: transfer information about where the data should go.  Data bus: transfer actual data to the desired address.  Control Bus: carries commands from the CPU to other parts (what they must doing). 5- Graphics Acceleration: it has processor and special memory for displaying graphics. 6- Number of Running Applications: if you run many applications at the same time the performance will be decrease.