⌨️Computer Science 1.1-1.6 (Paper 1) Flashcards
You can edit cards if I forgot something, flashcards based on the OCR J277 spec document
1.1.1 - What happens in the Fetch stage of the FDE cycle?
Address of next instruction is loaded into MAR and PC is incremented by 1
1.1.1 - What is the ALU and what does it do?
Arithmetic Logic Unit - performs arithmetic and logical calculations
1.1.1 - What is the CU and what does it do?
Control Unit - Decodes instructions and organises the other registers
1.1.1 - What is the cache and what does it do?
Smaller, volatile primary storage which is faster to access than the RAM and stores frequently used instructions
1.1.1 - What are registers?
Specialised units in the CPU which store one piece of information each
1.1.1 - What is the MAR and what does it do?
Memory Address Register - stores the current memory address where data is to be retrieved from or stored to
1.1.1 - What is the MDR and what does it do?
Memory Data Register - stores the data that’s been retrieved from or will be stored to memory
1.1.1 - What is the PC and what does it do?
Program Counter - keeps track of the current instruction and increments which each clock cycle
1.1.1 - What does the accumulator do?
Stores the results of calculations
1.1.1 - What is the difference between data and an address?
Data is a value used in calculations, whereas an address describes where in memory the data is stored
1.1.2 - What are the 3 factors affecting CPU speed?
Clock speed, cache size, number of cores
1.1.2 - How does clock speed affect CPU performance?
A higher clock speed means more FDE cycles can be performed every second, so the CPU performs better
1.1.2 - How does cache size affect CPU performance?
A larger cache means more instructions can be stored with a faster access time, so it takes less time to retrieve instructions on average, leading to each instruction taking less time to execute on average ==> higher CPU performance
1.1.2 - How does number of cores affect CPU performance?
More cores allow the CPU to run more FDE cycles in parallel, increasing the CPU performance
1.1.3 - What is an embedded system?
A computer system which is designed for a specific purpose, e.g. automatic thermostat in a fridge, traffic lights. It is also part of another machine or computer.
1.1.3 - What are the typical characteristics of embedded systems?
Fast and efficient, streamlined for one task, low memory capacity
1.2.1 - Why do computers have primary storage?
It is faster to access than secondary storage
1.2.1 - What is RAM and what are its characteristics?
Random Access Memory - volatile, fast access time, random access (any part of it can be accessed at any time), low storage (usually around 4-16GB)
1.2.1 - What is ROM and what are its characteristics?
Read Only Memory - non-volatile, very small (a few MB), contains the boot loader which loads the OS from secondary storage
1.2.1 - Why might virtual memory be needed in a system?
So the system doesn’t crash if it runs out of space in RAM
1.2.1 - What is virtual memory?
When the RAM is full, part of the secondary storage is used as temporary RAM - processes currently in use have priority to be in RAM
1.2.2 - Why do computers have secondary storage?
To be able to store information in a non-volatile way, i.e. it won’t get wiped when the computer switches off
1.2.2 - Name 3 types of secondary storage
Optical, Magnetic, Solid-state
1.2.2 - What are the advantages of optical storage?
Shock resistant, lightweight, portable, low cost