1.2 Memory and storage Flashcards
What is primary storage (main memory)
The component of the computer that holds data and programs that are currently in use
What is the difference between volatile and non volatile
Volatile - data is lost when the power is turned off
Non volatile - the data remains when the power is switched off
What is Random Access Memory (RAM) and its characteristics
Holds all of the data and instructions that are currently being processed
It’s volatile
You can read and write to it
It is quicker to access than secondary storage
It has the largest capacity of all main memory
What is Read Only Memory (ROM) and its characteristics
Stores the boot up sequence (BIOS) for the computer
It’s non volatile
Written by the computer manufacturer
Usually stores the BIOS
Smaller capacity than RAM
What are the levels of cache
Level 1:
Usually a part of the processor itself. This cache has the lowest capacity, but the quickest access speed
Level 2:
Built into the processor along with level one. Level two is slightly slower to read, but has a higher capacity than level one
Level 3:
The slowest at reading and writing, but it is still roughly twice as fast as RAM
What is virtual memory
A part of the HDD that acts like RAM when the RAM itself is full. The data moves between RAM and virtual memory when it’s needed by the CPU
What is flash memory
Non volatile memory that can be read from or written to. Suitable for secondary storage
What is secondary storage
Any non volatile medium that holds data until it is deleted or overwritten
What are the things to look for when choosing secondary storage
Capacity - how much storage it provides
Speed - how quick it is to access files
Cost - how much is it
Portability - can it be transported
Compatibility - can it be used with your device
What are the types of secondary storage
Magnetic - positive and negative magnet charges are used to represent binary code on the surface
Optical - a laser beam is reflected off the disc surface, a difference reflection represents the binary code
Solid slate - floating gate transistors are used to represent binary code. There are no moving parts
What are the advantages and disadvantages of magnetic storage
Advantages:
Low cost
High capacity
Disadvantages:
Not portable
Fragile
What are the advantages and disadvantages of optical storage
Advantages:
Portable
Low cost
Reliable
Disadvantages:
Low capacity
What are the advantages and disadvantages of solid slate
Advantages:
High speed
No moving parts
Disadvantages:
Limited times to read/write
High cost
What are the units of data storage
Bit
Nibble (4 bits)
Byte (8 bits)
Kilobyte (1000 bytes)
Megabyte (1000 KB)
Gigabyte (1000 MB)
Terabyte (1000 GB)
Petabyte (1000 TB)
How to convert denery into binary and vice versa
Minus the number by the highest number in a byte and go down until you have nothing left
Add up all the numbers
How to convert denery to hexadecimal
Divide the number by 16 (if it’s past 9, use the alphabet (up to F)) and put the remainder next to the number/letter (up to 9 then up to F)
Multiply the left number by 16 and add the number/letter on the right
How to convert binary to hexadecimal
Split the byte into 2 nibbles, make them into the number/letter they need to be and put them together
Make it back into to nibbles and put them together
What to remember when adding binary numbers
0 + 0 = 0
0 + 1 = 1
1 + 1 = 0 r1
1 + 1 + 1 = 1 r1
What is an overflow
When the largest number that a register can hold is exceeded
What to do when you multiply/divide a binary number
Shift to the left/right
What is a character set and the two types
The range of characters a computer system can represent
ASCII - 8 bits for each character (256 in total)
Unicode - 6 nibbles for each character
What is metadata
Extra data about a file
How do you calculate file sizes
Text file - multiply the number of characters by 1.1
Image - multiply the area by 1.1
Sound file - multiply the sample with the length
What is colour depth and resolution
Colour depth - bits per pixel
Resolution - pixels per inch
