Computer Science - keywords/definitions Flashcards
What is the Internet?
A collection of devices that are connected through a system of routers and servers.
What is the WWW?
A collection of websites and web browsers
What is HTTP & what does it do?
Safety protocol, it transfers data between a client and a server in plain text.
What is HTTPS & what does it do?
Safety protocol, it uses encryption to protect data as it transfers between a client and a server.
What is digital currency?
Money that only exists online
What is a blockchain?
A digital ledger that records every transaction made in a specific digital currency.
What is the concept of decentralisation?
When something is not controlled by central authorities.
What are cookies?
Small text files that store data.
What are the functions of the WWW?
1) to render html
2) record user history
3) to store cookies
Purpose of the CPU
To fetch, decode, and execute
Function of the MAR
stores the address of the data to be fetched or written to the memory
Function of the MDR
Holds the data that has been fetched or written to the memory
Function of the CIR
Stores the current instruction the CPU is decoding or executing
Function of the Program Counter
Stores the address of the next instruction to be fetched from the memory.
Function of the Accumulator
Temporarily stores the results of the calculations that have been performed by ALU (Arithmetic Logic Unit)
What is a register?
small amounts of high-speed memory that is contained in the CPU.
Function of the Control Unit
to send control signals to different components instructing them on what to do
Function of the ALU (Arithmetic Logic Unit)
Performs calculations that are required to do, in order to execute instructions.
Function of ROM
To store the instructions the computer executes when it is turned on.
Function of RAM
To store data, instructions, and software.
Difference between ROM and RAM
ROM is non-volatile.
How does a computer fetch, decodes, and executes instructions?
1) Program counter check for the address of the next instruction to be executed.
2) The contents of the Program Counter will then be copied into the Memory Address Register.
3) The control unit sends a memory read request to the main memory through a control bus.
4) The address is sent through an address bus from the Memory Address Register to the main memory.
5) The contents of the Main memory will be sent down through a data bus into the Memory Data Register.
6) The contents of the MDR will be then copied into the current instruction register.
7) The CIR then inspects and decodes the instruction.
8) The instruction is then carried out by the ALU performing a calculation or storing the information back into the main memory.
Primary storage
Storage that is directly accessible by the CPU.
What is primary storage made of
made of RAM, Cache, and ROM
What is Cache
small amount of memory that is situated near the CPU.
What is secondary storage
Storage that is not directly accessible by the CPU, used for permanent storage of data
How do Hard Disk Drives work
There are plates that spin at a high speed, a read or write arm is controlled by an actuator. The actuator head is moved towards the location of the data, and the data is written or read to by electromagnets.
How do Solid State Drives work
Made of transistors, uses NAND and NOR gates to control the flow of electrons
How do Optical storage (CD’S) works
A laser is shined at the disk and processing the reflection, an arm moves the laser across the disk. The laser burns the data into pits and lands. the laser is also used to read the data. When the laser shines where the pit changes into land or vice versa, this indicates a change in binary value.
What is virtual memory
secondary storage is used to act as RAM
What is Page Switching
Data than needs to be accessed by the CPU is switched by the operating system from virtual memory into ram and an inactive page from RAM replaces it in virtual memory.
What is Cloud storage
method of data storage where data is stored on remote servers.
3 types of Cloud storage
Public, Private, and Hybrid
What is public cloud storage
Customer and storage provider are different companies
What is Private cloud storage
Storage provided by a dedicated environment behind a company firewall, customer/company are integrated and act as a single entity.
What is Hybrid cloud storage
Combination of Public and Private: sensitive data will be stored privately, whereas less sensitive data will be stored in a public cloud storage provider.
NIC
connects a device to a wired/wireless network
what do NICS contain
MAC - generated at the manufacturing stage
MAC address
used to route frames on a local area network
2 features of MAC addresses
- address is unique to every NIC
- MAC is static
IP address
used to route packets on a wide area network
feature of IP addresses
not always static
Difference IPv4 and IPv6
IPv4 made of 32 bits and IPv6 made of 128 bits, so IPv4 cannot generate enough unique static addresses.
Router
Sends data between networks
2 jobs of a router
- use devices IP address to route traffic to other routers
- can assign IP addresses to devices on a local network.
Virus
simple program made to harm the user’s computer
pharming
malware being downloaded on a user’s device without the user knowing
Phishing
sending emails that appear to come from a reliable source and try to get a users confidential information.
Pre-condition loop
while loop - while a condition is true
Post-condition loop
Repeat….. until loop - repeats until a condition is true
Count-controlled loop
Repeats a loop a set number of times
Normal data
all values are accepted
Boundary data
Accepted -> upper and lower limits of the accepted range.
Rejected -> values outside of the range
Extreme data
Upper and lower limits of the accepted range
Abnormal data
Values that are outside of the range / different data type
Validation
when the computer checks if the data that has been inputted is reasonable
Verification
checking the data has been accurately copied from one source to another.
example of validation
Length check, validation check, type check
example of verification
when a user manually verifies the data.
why is it important for a programmer to use both validation and verification methods
Helps the programmer easily identify mistakes within their program.
