paper 1 - section 1 Flashcards
What is the purpose of a computer?
to take in data, process it, and then output it
What is hardware?
the physical components of the computer system, like the CPU, motherboard, monitor and printer
what is software?
the programs or applications that a computer system runs e.g. an operating system, a word processor or video game
What are embedded systems?
computer systems with a dedicated function within a larger mechanical or electrical system
What is a cpu?
A CPU (Central Processing Unit) is the “brain” of the computer system - it processes all of the data and instructions that make the system work
what are the three main parts of the CPU?
The control unit (CU), the arithmetic logic unit (ALU), and the cache.
What does the control unit do? what’s its main job?
It controls the flow of data inside and outside the CPU. It’s main job is to execute program instructions by following the fetch-decode-execute cycle.
What does the arithmetic logic unit (ALU) do?
All the calculations - it completes simple addition and subtraction, compares the size of numbers and can do multiplications and divisions using repeated addition and subtraction. It also performs logic operations such as AND, OR and NOT, and completes binary shifts.
It also contains the accumulator register.
What is the cache?
Very fast memory in the CPU - it stores regularly used data so that the CPU can access it quickly the next time it’s needed. When the CPU requests data. it checks the cache first to see if the data is there. if not, it will fetch it from RAM
What does the program counter (PC) do?
It holds the memory address of the instruction for each cycle.
What does the memory address register (MAR) do?
it holds any memory address about to be used by the CPU. the address might point to data or a CPU instruction.
what does the memory data register (MDR) do?
it holds the actual data or instruction. this may have been fetched from memory, or be waiting to be written to memory
what does the accumulator do?
stores the results of the calculations in the ALU
What happens in the “fetch” part of the fetch-decode-execute cycle?
1) The memory address is copied from the program counter to the MAR
2) The instruction stored in the MAR address is copied to the MDR
3) the program counter is incremented (increased) to point to the address of the next instruction, ready for the next cycle
What happens in the “decode” part of the fetch-decode-execute cycle?
The instruction in the MDR is decoded by the CU. The CU may then prepare for the next step, e.g. by loading values into the MAR or MDR
what happens in the “execute” part of the fetch-decode-execute cycle?
The instruction is performed. This could be: load data from memory, write data to memory, do a calculation or logic operation (using the ALU), change the address in the PC, or halt the program.
name five hardware components of a typical desktop computer.
any five from:
- power supply
- case cooling fan
- CPU
- Heat sink
- Optical drive
- RAM
- hard disk drive/HDD
- graphics card/GPU
- Motherboard
What is RAM?
High speed, volatile memory - it’s where all data, files and programs are stored while they’re being used
what is virtual memory?
a part of secondary storage that is used as extra RAM
CPU performance depends on what three factors?
Clock speed, number of cores, and cache size
what is clock speed?
The number of instructions a single processor core can carry out per second (Hz). The higher the clock speed, the greater the number of instructions that can be carried out.
How does the number of cores affect the performance of a CPU?
Each core can process data independently of the rest, so the more cores a CPU has, the more instructions it can carry out at once, so the faster it can process a batch of data
What is the cache and how does its size affect the performance of a CPU?
The cache is data storage inside the CPU that’s much faster than RAM. A larger cache gives the CPU faster access to more data it needs to process
Why can too little RAM cause a computer to run slowly?
The less RAM there is, the more the computer has to use virtual memory, which is much slower than RAM.
The more RAM a computer has, the more applications or more memory-intensive applications it can smoothly run, making it faster overall
what is a GPU?
GPUs (Graphics Processing Units) are specialised circuits for handling graphics and image processing. They relieve the processing load on the CPU, freeing it to do other things
what is primary storage? (main memory areas)
the main memory areas that the CPU can access very quickly, such as CPU registers, cache, ROM and RAM. Primary storage has the fastest read/write speeds and is mostly volatile
what is secondary storage? is it faster or slower than primary storage?
non-volatile memory that stores all data that’s not in use. Read/write speeds are much slower than primary storage.
How does a hard disk drive (HDD)/magnetic hard disk work?
A hard disk drive is made up of a stack of magnetised metal disks spinning at a rate of between 5400 and 15000 revolutions per minute. Data is stored magnetically in small areas called sectors within circular tracks. Read/write heads on a moving arm are used to access sectors on the disks.
What are the advantages of Magnetic Hard Disks/HDDs compared to SSDs?
- They are cheaper
- They are very high-capacity
- They have a longer read/write life than SSDs
What are the negatives of magnetic hard disks/HDDs?
They aren’t very durable and are easily broken because of their moving parts. They also aren’t very portable, and can not be carried around easily
What are solid state drives (SSDs)?
storage devices with no moving parts. Most of them use a type of flash memory. They are used for the same purpose as HDDs - for internal storage
What is flash memory?
a very common type of non-volatile memory that stores data in electrical circuits by trapping electrons
which have a faster read/write time - HDDs or SSDs?
SSDs
What are the advantages of SSDs?
- They are faster than HDDs
- They don’t need defragmenting
- They are more shock-proof than HDDs
- They are silent
- They have quite a high capacity
How much data can CDs hold?
around 700 MB
How much data can DVDs hold?
around 4.7GB
How much data can Blu-Ray disks hold?
around 25 GB
what are the three forms that optical disks come in?
read only, write-once, rewritable