Computing Components

What is a magnetic disk?

- A cross between a CD player and a tape recorder - Has a read/write head - The heads go directly to the information desired - It is organized into tracks and sectors

What are the advantages and disadvantages of a magnetic disk?

- It is direct access - Expensive than magnetic tapes. - Must be stored in a dust-free environment in order to protect them from crashing down. - More susceptible to breach of security and access gain to sensitive online disk files from remote terminals.

What are the advantages and disadvantages of magnetic tapes?

- Magnetic tapes are reliable and cheap. They can be used for backup and have a lot of storage space. - To access data in the middle of the tape, all the data before it must be accessed.

How does data flow in a von Neumann machine?

- Parts of a von Neumann machine are connected through wires called a bus - Each bus carries three kinds of information: address, data and control - An address is used to select the memory location to put data in or take data from - Data then flows between the CPU, main memory and I/O devices - The control information manages the movement, such as direction - The bus width is the number of bits that can be transferred simultaneously - The wider the bus, the more address, data or control bits it can move at once - Because memory accesses takes time, many modern devices provide cache memory - Cache memory is a small amount of fast-access memory (usually in the CPU) where frequently used data is stored - Before main memory is accessed, the CPU checks if the needed data is in the cache

What is a magnetic tape?

- The first truly mass auxiliary storage device was the magnetic tape drive - These are similar to a tape recorder and are often used to back up data from other secondary storage devices

What is the program counter?

- The program counter (PC) contains the address of the next instruction to be executed

What are the advantages of DVDs compared to CDs?

- They have more storage space than CDs

What is the fetch-decode-execute cycle?

- To start the FDE cycle, the address of the first instruction is loaded to the progam counter - Fetch the next instruction, decode the instruction, get data if needed, execute the instruction.

What is the difference between a CD and a magnetic disk?

A CD is an optical device, whereas a magnetic disk is a magnetic device. A magnetic disk stores data in a series of concentric tracks, while CDs have one track that spirals from inside out. The data on a magnetic disk is read with the help of a read/write head, while a CD is read using a laser beam.

What is a Surface Acoustic Wave touch screen?

A SAW touch screen is a screen with crossing horizontal and vertical high frequency sound waves

What are tracks?

A concentric circle on the surface of a disk

What is a DVD and what are the different types?

A digital versatile disk (DVD) has large storage capacity and is good for storing both audio and videos - DVDs can come in + and - types; these are simply two competing "brands" DVDs also come in R and RW formats, like CDs - DL-DVDs have "double layers" and have double the storage capacity

What is an SSD?

A form of flash memory

What are secondary storage devices?

A secondary storage device refers to storage devices other than the main memory. These are important because the main memory consists of the RAM and ROM — information cannot be stored here for long-term purposes, as RAM is volatile and data cannot be written into ROM. Secondary storage devices can also store large quantities of data.

What are sectors?

A section of a track

What is the Front-Side Bus (FSB)

A set of wires the processor uses to connect to the outside world.

What is a touch screen?

A touch sceen displays text and graphics like a regular monitor but can respond to the user touching the sceen with a finger or stylus These can serve as both input and output devices

Which efficiency is the most important when deciding on a storage device?

Access time

What is addressability?

Addressability is the number of bits we can store in each cell. Most modern computers are byte addressable

What are input and output units?

An input unit is a device through which data and programs from the outside world are entered into the computer An output unit is a device through which results are stored in the computer are mode available to the outside world

What is a screen?

An output device. When the inches of a screen are given, it is a reference to the diagonal measurements of the screen.

What are blu-rays?

Blu-ray disks are essentially DVDs with even larger capacity. Instead of a red laser, it uses a blue laser. Blue portion of lights have higher wavelengths and can transfer more information than red portion of lights

What is a capacitive touch screen?

Capacitive touch screen is a screen is made up of a laminate applied over a glass screen

What are CDs and what are the different types?

Compact disks use a laser to read information stored optically on a plastic disk, data is evenly distributed around a singal spiral track - CD-DA stands for "digital audio" and is used for audio recordings; some sectors on the disk are used for timing information - CD-ROM is similar to CD-DA, except the sectors used for timing information in CD-DA are used for other data - CD-R stands for "recordable" and allows data to be written once after manufacturing - CD-RW stands for "rewritable" and allows data to be written and rewritten an unlimited number of times

What is a USB?

Flash drives use nonvolatile computer memory and are plugged into a universal serial bus (USB) port (They can be erased and rewritten)

What is an infrared touch screen?

Infrared touch screen is a screen with crossing horizontal and vertical beams of infrared light

What is the central processor?

It is the brain of the computer, hence the most important part.

What is a Hard Disk Drive?

Magnetic disk drives that are used for permanent data storage

What does it mean to 'Execute the instruction'?

Once an instruction has been decoded and any extra data fetched, the control unit is ready to execute the instruction. It involves sending signals to the ALU to carry out the processing. When the execution is complete, the cycle begins again with the next instruction.

What is the difference between RAM and ROM?

RAM (Random Access Memory) is memory in which each location can be accessed and changed whereas ROM (Read Only Memory) is memory in which each location can be accessed but not changed. RAM is volatile while ROM is not - this means that RAM does not keep the data it contains when the power is turned off, but ROM does. Because it cannot be changed and is not volatile, ROM is often used to store the instructions a computer needs to start itself.

What are revolutions per minute?

RPM stands for Revolutions Per Minute. This refers to the number of times the disk will spin to transfer data.

What is a RAM?

Random Access Memory - RAM is the computer's main memory - It is called "random access" because it can be accessed directly instead of sequentially - The memory is volatile

What is ROM?

Read Only Memory - ROM is non volatile - Each location can be accessed but cannot be changed

What is a resistive touch screen?

Resistive touch sceeen is made up of two layers of electrically conductive material

What are the 4 terms to describe efficiency?

Seek time, Latency, Access time, and Transfer rate.

What is a cache?

Small, fast memory built into the processor (memory is not connected to the processor, you need to "get on a bus" to get there. Cache, on the other hand, is inside the processor)

What are blocks?

The information stored in a sector

What is the Arithmetic and Logic Unit (ALU)?

The ALU performs basic arithmetic operations and logical operations - Arithmetic operations include addition, subtraction, multiplication and division - Logical operations include NOT, AND, OR etc - Most modern ALUs have special storage units called registers that can be accessed faster than memory - Registers are used to store little pieces of information that are needed again immediately

What does it mean to 'Fetch the next instruction'?

The control unit goes to the address of the next instruction in the main memory and loads it onto the instruction register.

What is the instruction register?

The control unit organizes the actions of the other components and manages the fetch-execute cycle - There are two special registers in the control unit - The instruction register (IR) contains the instruction being executed

What does it mean to 'Get data if needed'?

The instruction to be executed may require additional data in the memory to complete its task. If so, the control unit must get the contents from the memory address. The ALU does the computations

What is memory?

The memory unit holds the data and instructions Memory is a collection of cells, each with a unique physical address Inside, there are contents

What is transfer rate?

The rate at which data moves from the disk to memory

Define the steps that a hard disk drive goes through to transfer a block of data from the disk to memory.

The read/write head of the disk drive is positioned on an arm that moves from one track to another. An input/output instruction specifies the track and sector. When the read/write head is over the proper track, it waits until the appropriate sector is beneath the head; it then accesses the block of information in that sector.

What are cylinders?

The set of concentric tracks that line up under one another.

What is access time?

The time it takes for a block to start being read; the sum of seek time and latency

What is seek time?

The time it takes for the read/ write head to get positioned over the specified track

What is latency?

The time it takes for the specified sector to spin to the read/write head

What is von Neumann Architecture?

There is no difference in data and its instructions so we can store them all together

What does it mean to 'Decode the instruction'?

To execute the instruction in the instruction register, the control unit has to decode the type of instruction it is (because it is in binary). The instruction is decoded into control signals used by the circuitry itself.

What powers do we use for time and storage?

We use powers of 10 for time and powers of 2 for storage

How does a capacitive touch screen work?

i. Laminate conducts electricity in all directions; a very small current is applied equally on the four corners ii. When the screen is touched, current flows to the finger or stylus iii. The location of the touch on the screen is determined by comparing how strong the flow of electricity is from each corner iv. Capacitive touch screens will not work if you are wearing gloves

How does a resistive touch screen work?

i. One layer has vertical lines, the other has horizontal lines ii. When the top layer is pressed, it comes in contact with the second layer, which allows electrical current to flow iii. The vertical and horizontal lines that make contact tell the location on the screen that was touched

How does a SAW touch screen work?

i. Sensors on opposite sides of the screen detect the sounds waves ii. When the user touches the screen, the location of the interruption of the sound wave can be determined

How does an infrared touch screen work?

i. Sensors on opposite sides on the screen detect the beams ii. When the user breaks the beams by touching the screen, the location of the break can be determined