Must Know! Flashcards
(37 cards)
What does the control unit do?
It is a part of the CPU that is responsible for:
- It decides which instructions to carry out next and fetches it
- It decodes instructions to work out what needs to be done to execute the
- It informs other parts of the CPU, what needs to be done in order for the instruction to be executed. It does this through sending control signals
- it synchronises the actions of the processor using its internal clock
Trace tables
When constructing one:
-Each variable must have a column
- Each mode of selection must be accompanied by a Boolean value,
e. g. If a => 0. This would have the column a => 0 and each row would have a Boolean value.
-Also each loop must have its own column. A count controlled loop must have integers in it’s rows. The other loops would have Boolean values in the rows as they are condition controlled
What does the memory unit do?
It stores everything that the computer is gong to use and the data needed for the CPU to carry out instructions
What does RAM do?
The RAM is the volatile memory within the memory unit of the CPU
-It’s job is to store program’s that are being used by the computer
What is ROM and what does it do?
ROM is the nonvolatile memory of the memory unit in the CPU
- the memory cannot be altered. It tends to be of a small capacity as it doesn’t have to hold large amounts of data
- It consists of program’s that’s allow the computer to start, such as the boot strap loader
How do CDs and DVDs work?
A laser reflects on the CD or DVD and the reflection is read on a pitted surface , this is how information is read from an optical disc
What does RW mean (optical disks)?
It mean that the contents of the CD or DVD can be erased or rewritten
-this can be used to store back up records that need to be updated on a regular basis
What does ROM mean (Optical disks)?
This means that the contents of a CD or DVD be altered
- Manufacturers have tended to use CD ROMs to distribute software and for large data files, such as encyclopaedias
- Data rich systems are more likely to be DVDs than CDs as they provide greater storage capacity
What does R mean (optical disks)?
It indicates read only and these discs only allow data to be written once, and then it cannot be altered. Although the disc may be written many times until the capacity is full
-This may be a more appropriate storage media for archive as it eliminates the possibility of content being accidental erased
What is a DVD RAM disc?
This is very much like the disc RW but data are stored in a different way, which means:
- the surface can be written to far more often than the surface of a DVD RW
- Access and reading time is much faster
- Reading and writing can take place simultaneously
What is a Blu-ray Disc?
This is an optical storage media which has a much larger storage capacity than any other optical storage media, while at the same time being able to provide high speed data transfers
What is a buffer?
This is a small amount of fast memory used as a temporary store.
- The processor can send data to the buffer, or receive data from the buffer very quickly.
- If there is more data than will fit the in the buffer, an interrupt is sent to the processor
- Every device has a buffer
Hat is an interrupt?
This is an electronic signal sent to the processor, requesting the CPUs attention.
-any hardware device can send an interrupt
What is the keyboards job?
To use keys to generate different character codes that the computer recognises and is within the character set
- Keyboards are the most common form of input device to a system because they are universally available and understood
- Natural or ergonomic keyboards have been developed to with a curve to make keyboards more comfortable to use
What is a concept keyboard?
This is a touch sensitive keyboard, which has keys as part of a continuous surface which has pressure sensitive areas.
- The concept keyboards are programmed so that the individual keys represent things within an application software, such as the concept keys used in fast food restaurants to input orders
- This keyboard is less prone to damage and is well suited to a greasy environment
What is a MIDI keyboard?
This is a musical instrument digital interface keyboard. It is normally arranged like a piano keyboard
What does a mouse do?
A mouse is designed to be used as a pointer on a screen. It is helpful as it mimics the human action of pointing.
- It serves two purposes, to provide an analogue input from physical movement and a digital input from the mouse button
- There are also other variations that have been developed, such as track balls and touch pads that serve the same purpose
What does a bar code reader do?
This is a scanner that reads laser light reflections from dark and light lines of varying thickness. The pair of lines make up a code that can be converted into a number
- When a barcode is scanned, the level of reflected lines light is captured as an electronic signal and converted to a digital reading
- Barcodes can be easily misread, therefore the check digit is there to ensure that the barcode has been read properly
What does an optical character reader do?
This is a device that can read and distinguish the different characters in a given character set. This is done by reading and comparing the shape of the characters to that of the ones in the character set
What is an optical mark reader?
This is a device that can recognise the presence of a mark on a sheet of paper. It’s position is scanned and converted to a digital reading
What is the main advantage of both OCR and OMR ?
Data can be input to a computer system without having to be transcribed, thereby reducing the number of errors at the data capture stage
What is a scanner?
This is a device that converts a document into pixels. The largest the number of pixels, or the smaller each individual pixel, the better the definition of the final picture
What is a graphic tablet?
This is a flat glass surface on which the user can draw with a special pen. The tablet works by sensing where the pen is pointing and converts the movements of the pen to a digital reading that is interpreted by the software
What are the uses of a microphone?
A micro phone can can be used to input sound into a computer. The sound can be used to provide an audio commentary for a slides how or they can be converted to text.
- An advantage of speaking into the computer is that input is more intuitive than typing at a standard keyboard
- Software on a computer can convert the audio of the spoken word into digital form for use in a word processor.
- The disadvantage is that the software used to translate the spoken word into text can be unreliable
