3 Flashcards
Input devices
Laptop: keyboard, buttons, microphone
Smartphone: microphone, buttons, GPS sensor, touch part of the touchscreen
Output devices
Laptop and smartphone: speakers, display
Processing
CPU (Central Processing Unit)
The main components
of a computer
-Input devices
-Output devices
-Main memory
-Secondary storage
-CPU (central processing unit)
The purpose of the CPU
it has to execute and processing all of the instructions and data
Von Neumann architecture
Used the concept of ‘stored program computer’ which allowed the instructions and data to be stored in the same memory
Components of the CPU
Control Unit (CU)
Arithmetic-Logic Unit (ALU)
Register
Control Unit (CU)
The control unit coordinates and controls all of the activities taking place within the CPU
- It decodes instructions and executes them
- It receives signals from the system clock
- It directs the timing and control of other parts of the CPU
Arithmetic Logic Unit (ALU)
The ALU is where the actual arithmetic operations are done (can be more than one)
Registers in the CPU
Program Counter (PC)
Memory Address Register (MAR)
Memory Data Register (MDR)
Current Instruction Register (CIR)
Accumulator (ACC)
Program Counter (PC)
The Program Counter stores the address of the next instruction to be executed.
Memory Address Register (MAR)
The MAR stores the address of the current instruction being executed and the address of the data that
needs to be accessed.
Memory Data Register (MDR)
The MDR holds first the instruction, and then the data (if any) to be used in the instruction, copied from RAM.
Current Instruction Register (CIR)
The CIR stores the instruction currently being executed or decoded
Accumulator (ACC)
The accumulator (ACC) is where arithmetic and logic results are temporarily stored (result from ALU calculation)
Fetch – Decode – Execute
system is used by the CPU
FETCH – causes the next instruction and any data involved to be fetched from main memory
DECODE – decodes the instruction
EXECUTE – the instruction is executed
REPEAT
Register
a fast memory located in CPU
The CPU operates on a cycle.
What is the name of this cycle?
Fetch-decode-execute cycle.
Explain the different stages of the cycle
Fetch: The CPU fetches the next instruction to be executed from main memory.
Decode: It decodes the instruction
Execute: The processor carries executes the instruction.
THE PROCESS IS REPEATED
Factors affecting CPU performance
Clock speed
Number of cores
Cache size
Clock speed
- Cycles per second
measured in hertz (Hz) - Everything in a computer happens on the pulse of the internal clock
- Therefore, the faster the clock speed, the faster the instructions are processed
Processor of cores (A dual-core computer)
A dual-core processor has the potential to perform two instructions at the same time
This allows twice as many instructions to be executed
Cache
- Cache is a small amount of very fast, expensive memory in the CPU
- It can be accessed faster than regular main memory (RAM)
Difference of Cache and RAM
-RAM is relatively slow memory to access as it is further away from the processor than cache
-Program instructions and data that are fetched are stored in cache in case they are needed again soon
The benefits of cache
cache is available extremely quickly (faster than RAM)
How does clock speed affect performance?
if the clock speed increases there will be more instruction per second, more Hz. This means that CPU performance will be better.
How does number of cores affect performance?
increase the number of chores the performance of a CPU is better
How does cache affect performance?
if Cache size increases more data can be loaded and stored so CPU can access data quicker which can increase performance
Levels of cache memory
Level 1- cache is extremely fast but small
Level 2- It is very fast, but a little slower than Level 1 cache
Level 3- cache is the slowest type of cache, but still faster than RAM. (can store more data)
Describe how the use of cache in a computer system can affect the
performance of the CPU.
Cache is faster to transfer data from than RAM .
The processor will first try to access data in cache.
Cache has different levels. The faster levels are tried first.Increasing the amount of cache will increase the number of hits which will increase the performance of the CPU.
What are buses?
A bus is a collection of wires through which data or control signals are transmitted from
one component to another.
Types of buses?
Address bus- Responsible for transferring theaddressof the
memory or device to be read from or written to.
Control bus- Carries control signals to coordinate the activities of the CPU
Data bus- carries data throughout the computer system
Embedded system
a single processor that includes, RAM, ROM and processor as one unit
Car embedded systems
Interior fans and temperature
Interior lighting
Other embedded systems
Security systems
Lighting systems
Vending machines
Opcode and operands
The opcode is the instruction and the operands are the values that the instruction works on
ACSII and Unicode
(American Standard Code for Information Interchange) has become the standard code, used worldwide
Types of primary storage
RAM (Random Access Memory)
ROM (Read Only Memory)
RAM
-RAM stores programs or data that are running
-It is directly accessed by the CPU
-RAM is volatile as it loses data if the power is off
ROM
- non-volatile (permanent memory)
- stores basic startup instructions for a computer, e.g. basic input/output system (BIOS).
- data contents can only be read; cannot be altered.
What is initially stored in the RAM
- Operating system
-When applications or programs are loaded, they are copied into RAM from the hard drive
What happens when RAM runs out of space?
Virtual memory is part of the hard drive used as an extension to RAM
An area of a hard drive / secondary storage is allocated to be virtual memory.
If more programs/data needs to be stored in RAM than there is space for some programs/data can be copied to virtual memory to free up space
Programs may then be swapped between RAM and virtual memory
Advantages and disadvantages of virtual memory
it is cheap and help with storage but is very hard and slow to access
Explain why increasing the amount of RAM will improve the performance of a PC.
It will be better because you can load more data to the RAM meaning the CPU can access more data faster
Secondary storage
Hard Disk Drive (HDD)
Solid State Drive (SSD)
Storage methods
Magnetic: Mechanical parts move over the disks surface to read and write data magnetically, or a drive head reads a magnetic tape
Optical: Lasers read and write data using light
Solid State: Data is recorded onto solid memory chips without any moving parts
advantages and disadvantages for Magnetic storage
Cheap, large storage capacities
Lots of mechanical parts, durability an issue, not very portable
magnetic storage work
- Data is stored on a platter (magnetic surface coated with iron particles) which are divided into tracks.
- The platter is spun.
- Have actuator heads that contain electromagnets.
- The actuator moves across the storage media.
Offline secondary storage
- CD/DVD/DVD-ram (optical storage devices)
- Blu ray disks
- USB flash memories.
- external HDD or SSD.
optical storage advantages and disadvaantages
Advantages:
Cheap, very easily portable, takes up little space physically
Disadvantages:
Less storage capacity compared to other types
Easily damaged / scratched, requires a CD reader
Slow write speeds
advantages and disadvantages of solid state storage
Advantages:
Highly durable, no moving parts, very fast read/write speeds, no noisy fan or drive arm, faster start up times
Disadvantages:
More expensive than magnetic hard disks, similar storage capacity as magnetic disks
Flash memory
Describe how a floating gate is used to store one bit of data.
- The floating gate stores data by trapping electrons inside it. This allows current to flow or not flow depending whether the electrons are trapped. If electrons are trapped a 0 is stored in the cell and if no electrons are trapped a 1 is stored in the cell
Describe how control gates are used to write a 1 to the memory cell.
-A negative voltage is applied to the control gate causing the electrons to be able to travel through the isolation layer. This results in no electrons in the floating layer. When no electrons are located in the floating gate the current is able to flow (from source to drain), which indicates that a 1 is stored in the memory
cell.
structure of flash memory
- control gate on top
-isolating layer
-floating layer
-isolating layer on bottom
cloud storage
Storing data on the Internet, remote storage provided by a company
scalability
The ability to easily increase the size of computing storage
redundancy
where multiple copies of files are stored in different locations
data centre
centralised collection of servers stored inside a building
Describe how cloud storage enables students to access their files.
Students would need Internet access to be able to access their files. To save a file, the file would be uploaded to the cloud storage provider. It will then be stored on a remote
server which is located at a data centre. The file may be replicated at a number of different locations for redundancy. To open the file, it will first need to be downloaded.
Explain two advantages of using cloud storage for students’ files.
Students will be access their files from anywhere with an Internet connection allowing
them to access resources when not in school.
Storage space can be increased without buying new servers / scalability.
Data stored in multiple locations / redundancy meaning that it is highly unlikely for data to be lost
Explain one disadvantage of using cloud storage for students’ files.
If the cloud storage provider had an outage / the Internet connection is lost to the school and students wouldn’t be able to access any of their files.
With many students trying to access files at the same time it may take a long time to download/access them leading to frustration and loss of time.
