1.2 Memory and storage Flashcards
Why do computers need primary storage?
It holds data and instructions which the CPU needs to access while a computer is running. Plus to access this data is faster then secondary.
What is the RAM?
Random access memory
Volatile (loses memory when powered off) Holds the operating system, programs and data in use by the CPU.
What is the ROM?
Read only memory
Non volatile (doesn’t lose memory when it has no power) Contains the very first instruction for the computer (bootstrap)
What is the similarity and difference of RAM and ROM ?
similarities: - hold information - Both presented in binary form Difference: Ram is volatile Rom is non-volatile Ram can read and write Rom is read only
if the RAM runs out of storage where is data stored?
virtual memory
Why might virtual memory be needed in a system?
To allow space in the RAM to store data.
What is virtual memory?
non-volatile and secondary memory created to store data when RAM storage is full
How does virtual memory work?
Memory is transferred from the RAM to the hard drive where virtual memory is stored .
Why do computers need secondary storage?
- it stores the programs when switched off
- back up of data files
What is the common types of storage?
Optical
Magnetic
Solid state
What are the advantage and disadvantage of optical storage?
Advantages: -cheap - portable Disadvantage: - not durability (can easily be scratched) - speed is slow
What are the advantages and disadvantages of magnetic storage?
Advantages:
- cheap
- large capacity
disadvantages: - fragile
- slow access time
What are the advantages and disadvantages of solid state drives?
Advantages: - durable - fast access Disadvantages: -expensive - limited read and writes
What is an example of magnetic, solid state and optical storage?
magnetic - hard disk drive
Solid state - flash memory cards, SSD, memory stick
Optical - DVD and Blu-ray
How do you calculate text file size?
Bits per character x Number of characters
How do you calculate a sound file size?
Sample rate x duration (secs) x bit depth
How do you calculate a image file size?
colour depth x image height x Image width
What are the unit of data storage?
The units of data storage: Bit Nibble (4bits) Byte (8 bits) kilobyte (1,000 bytes or 1KB) Megabyte (1000 KB) Gigabyte (1000 MB) Terabyte (1000 GB) Petabyte (1000 TB)
How do you convert denary to binary?
The table goes from 128, 64, 32, 16, 8, 4, 2, 1 and you start right to left
How do you convert binary to denary?
Use the table to add up the values.
How do you convert denary to hexadecimal?
You make it binary. Then make it into a nibble (2 sections) then put 1, 2, 4, 8 then add up the values. If the value is 10 or over use the alphabet so A and so on.
How do you convert hexadecimal to denary?
The first digit you times by 16 then the second one you add on.
What are the rules of binary addition?
0+0=0
0+1=1
1+1=0 carry 1
1+1+1=1 carry 1
What happens when you shift the binary to the left?
The binary is multiplied by 2
What happens when you shift the binary to the right?
The binary is divided by 2
What is a character set?
A character set is defined list of characters recognised by the computer.
What are 2 examples of character sets
ASCII (extended ASCII) and Unicode
what are the total number of characters in ASCII, extended ASCII and Unicode?
ASCII - 2^7 = 128
extended ACSII - 2^8 = 256
Unicode = 2^24 = more then 16 million
What is metadata?
Data about Data such as the file format, resolution and colour depth
How is the number of colours calculated?
2^n (n being the of bits for each pixel)
What is the effect of resolution and colour depth?
The greater the colour depth and resolution the larger the file size of the image.
If the sound is stored as analogue what must it be stored as?
It has to be stored in binary.
What is sample rate?
+ what is the sample rate measured in?
How many samples you take in a second
+
Hertz
What is bit depth?
The number of bits available for each sample.
What is the affect of higher bit depth and sample rate?
The higher the number of bit depth and sample rate the higher the quality of sound and the larger the file size.
what are the type of compressions?
Lossy and lossless compression
Why is data compression used?
To reduce the file size.
What is lossy compression?
Removes data permanently which affects the quality of the file.
What are the advantages and disadvantage of lossy compression?
Advantage:
- Greatly reduces file size
- commonly used meaning a lot of software can read lossy files
disadvantage:
- loses data that affect the quality of the file
- can’t be used on text
What is lossless compression?
Data is removed temporarily and can be restored to its original state.
What are the advantage and disadvantages of lossless compression?
Advantage: - quality of not affected - can be used on text and software files disadvantages: - only a slight reduction in file size
Type of file types that lossy compression uses
JPEG and MP3
Types of file types that lossless compression uses
PNG and TIFF
