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Flashcards in 4 - Computer Systems Deck (34):

What is a computer system?

A computer system takes a set of digital inputs, processes them and creates a set of outputs. This is done by a combination of hardware and software.



Hardware is the physical components that make up a computer e.g. keyboard



Software is human-written programs that contain instructions on how the hardware will operate


Role of the CPU

CPU processes data. It does this by fetching instructions from memory (RAM), decoding the instructions and then executing them


What does the CPU do as well as processing data?

The CPU controls all of the component parts of a computer e.g. the hard disk


Where is the CPU located?

In the motherboard


What are the 3 main parts of the CPU?

Control Unit
Arithmetic Logic Unit (ALU)


What is the role of the ALU?

To handle all of the data processing inside the CPU. The arithmetic part deals with arithmetic operations. The logic part deals with logic and comparisons.


What is the CPU clock?

A tiny quartz crystal inside the CPU chip that ticks at a steady speed. During each tick the CPU processes and executes a single instruction.


What are CPU clocks measured in/

They are measured in Hz. 1 GHz enables 1 billion instruction to process every second


What is Von Neumann architecture?

Von Neumann is where both the data and the software currently being used are stored in the RAM.


What does the Control Unit do?

It handles the movement of data and instructions around the computer.


What are buses and what do they do?

The buses are collections of wires through which data is transmitted from one component to another in a CPU


What is main memory (RAM)?

RAM is where the programs and data whilst in use are stored


What are registers?

Registers are a very small but fast type of memory which can hold a data value in use by the CPU


What is the fetch-decode-execute cycle?

The fetch-decode-execute cycle is where the CPU continuously reads instructions stored in main memory and executes them as required


How is the first instruction fetched?

The first instruction in the program is loaded (fetched) from main memory into the CPU.


How is the next instruction fetched?

The next instruction's location of the RAM is loaded into the program counter, and then is copied to the MAR. After this, the control unit copies the instruction from the MAR onto the address bus. The RAM then reads the contents of the location and loads it onto the data bus. The content is then loaded onto the Data bus and is copied to the MBR. After this, the instruction from the MBR is copied to the instruction register.


What registers are involved in the Fetch-Decode-Execute cycle?

Memory Buffer Register (MBR)
Program Counter
Instruction register
Memory Address Register (MAR)


How is the instruction decoded?

The control unit reads the contents of the MBR, and checks that it is a valid instruction. The CPU determines exactly which operation is to be executed.


How is the instruction executed?

The control unit sends signals to the ALU, which may perform a logic comparison or calculation.


How is the fetch-decode-execute cycle a cycle?

Once each instruction is executed, the control unit increments the program counter and uses it to find the next instruction to be fetched, and the cycle begins all over again.


What is the effect of clock. speed on the CPU?

The faster the clock, the more instructions the processor can complete per second. However, if this is too high it can cause the CPU to overheat.


What is a core?

A core is a complete processing unit within the CPU, which has an ALU, a control unit and registers.


What is the effect of the number of cores on CPU performance?

CPUs with multiple cores have more power and can therefore run a number of programs at the same time


What is cache?

Cache is a special type of memory which is volatile, and can be accessed much faster than RAM


What is the effect of cache size on CPU performance?

The larger the cache size, the better the performance because the computer is able to store more data


What is the effect of cache type on CPU performance?

Level 1 cache is extremely fast but relatively small
Level 2 cache is larger than level 1 but slower
Level 3 cache is a specialised memory that works to improve levels 1 and 2.
As cache speed increases, less memory is available


What are embedded systems?

A system that has computer hardware with software embedded in one of its components


What are some examples of embedded systems?

treadmill, ATM, car system, microwave oven, mobile phone, TV remotes, washing machines


How does an embedded system differ from a non-embedded system? (2 differences)

an embedded system doesn't load and execute other applications, which means the system is only able to run a single application, whereas non-embedded systems do

the software of an embedded system is custom-written, to work with its specific hardware. Non-Embedded systems are more general purpose


Non-embedded systems examples

Laptops, Desktops, Tablets


What is the purpose of an operating system?

An operating system primary purpose is to allow applications software to communicate with the hardware.


Where may the result of a fetch-execute cycle be stored?

The results of this may be stored in a register in the CPU, or may be returned to main memory if the program requires it.