Computer Systems (I) - Components of a Computer System Flashcards
What is a computer?
A machine that processes data
What is the purpose of a computer and why are they so beneficial?
The purpose is to take data, process it and output it – they are much more efficient than humans at certain tasks
What does a computer system consist of?
Hardware and software (working together to complete tasks)
What is hardware and what is software?
Give some examples
Hardware – physical components, e.g. CPU / motherboard / printer / monitor
Software – programs or applications that a computer system runs (e.g. an operating system / video games)
What are embedded systems?
Embedded systems are computers built into other devices, e.g. TVs / dishwashers
They are often used as control systems (monitoring / controlling machinery)
They are easier to design and cheaper / more efficient as they have a dedicated single task
What two types of computer system are there and what are their differences?
General purpose – designed to perform many tasks, e.g. a home PC
Embedded systems – designed to perform one specific function, e.g. controlling traffic lights
List some key components within a computer1
Power supply Cooling fans CPU Graphics card Optical drive RAM HDD / SSD Motherboard
What does CPU stand for and what does it do?
Central Processing Unit – processes all the data and instructions that make the system work
What are the 3 main parts to a CPU?
Control Unit (CU)
Arithmetic Logic Unit (ALU)
Cache
What is the function of the Control Unit (CU) within a CPU?
CU is in overall control of the CPU – manages fetching, decoding and execution of program instructions.
It also controls the flow of data inside and outside of the CPU
What is the function of the Arithmetic Logic Unit (ALU) within a CPU?
The ALU undertakes the calculations – additions / subtractions (and multiplications / divisions using repeated additions or subtractions)
It performs logic operations (AND / OR / NOT) and binary shifts
It also contains the accumulator register
What is the function of the Cache within a CPU?
Cache is very fast memory in the CPU (faster than RAM but slower than registers)
It stores regularly used data
There are three types: L1 (quickest but lowest capacity), L2 and L3 (slowest but greatest capacity)
What does the following show?
Von Neumann’s architecture for a CPU
CPU runs programs, stored in memory
Programs consist of instructions and data, stored in memory addresses
What are CPU registers?
Registers temporarily hold tiny bits of data needed by the CPU – they are very fast at reading / writing
What do CPU’s follow?
Fetch-Decode-Execute cycle
Describe the Von Neumann CPU design
Describe the Fetch part of the Fetch-Decode-Execute cycle
Fetch – copy memory address from Program Counter (PC) to Memory Address Register (MAR)
Copy instructions stored in the MAR to the Memory Data Registers (MDR)
Increment the PC to point to the next address of the next instruction, ready for the next cycle
Describe the Decode part of the Fetch-Decode-Execute cycle
Decode – the instruction in the Memory Data Register (MDR) is decoded by the Control Unit (CU)
The CU may then prepare for the next step, e.g. loading values into the Memory Address Register (MAR) or MDR
Describe the Execute part of the Fetch-Decode-Execute cycle
Execute – instruction is performed, e.g. load data from memory / write data to memory / perform a calculation or logic operation (using the Arithmetic and Logic Unit (ALU)) / change the address in the Program Counter (PC) or halt the program
What does RAM stand for and what are its properties?
Random Access Memory (RAM) is used as the main memory of a computer
It can be read and written to
It is volatile – temporary memory requiring power to retain the data
What does ROM stand for and what are its properties?
Read Only Memory (ROM) contains the instructions a computer needs to properly boot up
It can only be read from (though can be updated with a ‘flash’)
It is non-volatile – the memory is permanent, containing data even without power
What is virtual memory and why might it be used?
Computers have limited RAM – when full, data can be moved onto secondary storage (virtual memory)
This is a much slower process but will allow many programs or RAM intensive programs to run