OCR GCSE computer science

What is the purpose of the CPU?

executing instructions given in a program, where data process is, control other device(fetch-execute cycle)

What are the common CPU components?

ALU, CU, Cache, registers

What happens in the fetch part of the cycle?

instruction/data to be used moved from RAM to CPU, CPU send signal, request next instruction/data to be used.

What happens in the execute part of the cycle?

CU decode/interpret instruction&decide what it mean&action to perform, then it carry out. If calc need to be perform, CU instruct ALU.

What is the MAR?

holds address(loction in mem)of instruction/data to be fetch/stored

What is the MDR?

holds data/program instruction temporarily when fetch(mem)/data to be fetch/stored.

What is the program counter(PC)?

holds mem address of next instruction to be process

what is the Accumulator(ACC)?

memory location where operation carry out by ALU are temporary stored.

What is the cache?

temporary data/instruct store(likely need by CPU), so can be access quick when need

What is the ALU?

perform arithmetic/logic operation(+/-/*/division/logical test using logic gate/comparison/shift operation).

What is the Control Unit(CU)?

coordinate act in CPU, also of computer&control fetch-execute cycle by send control sig to parts of CPU. also send sig to other components of computer system.

What is the von neumann architecture?

hold both program/data in memory. Data would move between mem unit and CPU.

What happened before the von neumann architecture?

computer had to be rebuilt for each new program needed.

What way does the von neumann architecture execute program instructions?

fetch-execute cycle

What is the way the CPU is designed and executes program instructions called?

von neumann architecture

What is clock speed measured in?

cycles per second(hertz/Hz)

What is the speed at which CPU operates at called?

clock speed

What is the clock?

pulses sent to components to coordinate their act&ensure instruct carry out&complete. one instruct carry out with each pulse.

main factors affecting CPU performance?

clock speed, cache size, number of cores

What is the fastest cache size?

level 1 cache(L1), but the smallest memory capacity out of 2 more cache’s

How does cache help modern computers without increasing price?

increases speed at minimal costs.

What is a multi core processor?

has more than one CPU

Pros of multi cores?

work together on same program(parallel processing), work on diff programs at same time(multi-tasking)

cons of multi cores?

may not work together at same time on program, so tasks carried out in turns.

What are embedded systems?

small computer system built within large device to perform specific function. simple user interface(buttons)

Examples of embedded systems?

Washing machine, digital cam, fridge, TV

What are embedded systems limited to?

certain number of tasks, memory

Where are all the components in an embedded system located on?

single printed circuit board, built into a larger device(embedded system)

What does the memory in an embedded system contain?

the program

What is unique to an embedded system?

hardware components

What are programs often written in so that hardware components can be easily controlled using mini amount of memory&executed as fast as possible?

assembly/machine efficient language

Where is the program which controls the equipment/hardware components located in, inside an embedded system?

ROM, program can’t be changed

What does the embedded operating system not have to do when switched on?

loaded, as it held in ROM

Why do we need primary storage?

temporary store while its store run by CPU, access directly&quick by CPU when need. Also take long to fetch data/instruct from hard drive.

What is the difference between RAM&ROM?

RAM=(read-write)Volatile, when turn on, need basic startup routine from non-volatile, ROM=non-volatile(can’t write over content once create), store BIOS(bootstrap loader)to startup computer.

What does the BIOS do when the computer is first switched on?

controls what happens, checks hardware to ensure, & load basic software, so can communicate with them. It then locate and pass control to operate system.

What is ROM(physically)?

integrated circuit on chip, programmed with specific data to perform function.

What does the name of RAM mean?

random access, cause each mem location can access any order if address of location is specified. (means CPU can go any location=serial access)

Why is virtual memory needed by a computer?

when running alot of stuff at same time, RAM can be full, instead of closing these stuff, mem manager use virtual mem to store some data on hard disk drive.

How does virtual memory work?

process run on pc may need to store data on RAM, if no space, mem manager swap out least recent use data with virtual, and then new requested data is stored on the freed up RAM. If least recent used data needed, it swapped back into RAM at expense of other data.

What does the virtual memory store?

programs currently active.

Is virtual memory quick?

no