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computer sci 1
| Question | Answer |
|---|---|
| cu- control unit | overall control off the cpu. fetches and executes the program instructions by following FDE cycle. controls flow of data inside cpu (alu, registers, cache) and outside cpu (input/output) |
| ALU | perform all arithmetic and logic calculations contains accumulator register |
| cache | very fast memory in cpu, slower than registers, faster than RAM stores frequently. user data, so cpu can access quickly when needed. -low capacity and are expensive |
| what does the program counter do? | holds the memory address of the instruction for each cycle |
| what does the acc do | stores intermediate results of calculations in alu |
| what does mar do | holds any memory adress about to be used by cpu |
| what does mdr do | holds actual data or instruction thag may have been fetched from memory or waiting to be written to it |
| what does memory do? | holds program instructions and program data |
| FDR- Fetch | 1) copy memory adress from PC to MAR 2)copy instruction stored in MAR to MDR 3)Increment the PC to point to the address of the next instruction |
| FDE- Decode | instruction in mdr is decided by CU. CU then may prepare for next step, loading values into MAR or MDR |
| FDE- Execute | instruction is performed: 1) load data from memory, write data to memory, use ALU, change address in PC or halt the program). |
| what is clock speed | -no. of instructions a single processor code can carry our per second -higher the clcok speed, higher no. of instructions ^ |
| no. of cores | -each core in cpu can process data independently -more cores, more instruction it can carry out at once -most pc’s and smartphones have 4 or more cores these days |
| cache size | -larger cpu cache gives cpu faster access to more data it needs to process |
| RAM | -can mean faster or smoother system -without enough, will run slowly due to use of virtual memory -more ram = more applications/memory intensive applications it can run smoothly, faster overall |
| advanatges to using HDD’s | -cheaper -higher capacity than SSD’s -have a longer read/write life than SSD’s (can only be written a certain no. if times before deterioration) |
| advantages to SSD’s | -faster -don’t need defragmenting -more shock proof than HDD’s HDDs make some noise, SSD’s are silent |
| what are character sets | collection of characters that a computer recognises from their binary representation |
| ASCIII | -most commonly-used character set. -given 7-bit binary code, can represent total of 128 different characters. -an extra bit (0) is added to the start of the binary code for each ascii, so they all fit nicely into 1 byte |
| unicode | -several different forms and tries to cover every possible character or symbol that may be written -unicode uses multiple bytes for each character -first 128 codes in unicode are the same as ascii |
| how to work out size of text file? | file size (bits) = number of bits per character * number of characters |
| benefits of compression | -smaller files takes up less storage space on device -streaming and downloading from internet it quicker, take up less bandwidth -allows web pages to load more quickly in web browsers -email services normally have restriction on size of attachment |
| lossy pros | -greatly reduced file size, more files can be stored -takes up less bandwidth, can be downloaded and streamed more quickly -commonly used- lots of software can read lossy files. |
| lossy cons | -loses data, file cannot be returned to og -lossy compression cannot be used on text or software files -need to retain og -lossy files are worse quality than og |
| lossy examples | MP3 and AAC (audio) JPEG (image) |
| Lossless pros | -data is removed temporarily, no reduction in quality -lossless files can be decompressed back into og -lossless compression can be used on text and software files |
| lossless | -only slight reduction in file size, so still take up space. |
| lossless examples | -FLAC (audio) -TIFF + PNG (image) |
| what is LAN | -local are network. -covers a small geographical area located on a single site -either wired or wireless -often used in business, schools and universities -lots of homes use it to connect devices like printers tv’s pc’s |
| why use LAN? | -sharing files is easier -can share same hardware -internet conn can be shared between every device connected to LAN -can install+update software on all comps at once -can communicate w LAN users cheaply and easily -user accounts stores centrally |
Created by:
elisseu
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