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What is binary?
A number system using base-2 that represents numbers with 0 and 1
What is a bit?
The smallest unit of data that a computer can store and process; a logical state with two possible values, commonly representing a binary digit.
How many bits are in a nibble?
4
How many bits are in a byte?
8
What is two’s complement?
A method of representing signed integers, indicating whether the number is positive or negative with the most significant bit.
What is a logical binary shift?
When the digits in a binary number move to the left/right.
What is an arithmetic binary shift?
When the digits in a binary number move to the left/right, preserving the most significant bit.
What is the most significant bit?
The leftmost digit of a binary number.
What is hexadecimal?
A number system using base 16 that represents numbers 0 through 16 using digits 0 through 9 and letters A through F.
Why is hexadecimal used?
To represent large numbers using fewer digits
What is ASCII?
American Standard Code For Information Interchange
How many bits does ASCII use?
7
How many bits does Extended ASCII use?
8
How many bits does Unicode use?
32
What is ASCII used to represent?
The characters of the English language
What is Extended ASCII used to represent?
Other miscellaneous characters(e.g. accents)
What is Unicode used to represent?
Characters from languages all around the world
Why are ASCII/eASCII/Unicode used?
To represent text using binary
What is stored program concept?
When both data and instructions are stored in main memory
What does the arithmetic logic unit do?
Perform arithmetic and logical(boolean) operations
What are the five registers in Von Neumann Architecture?
The program counter(PC), the accumulator(ACC), the memory address register(MAR), the current instruction register(CIR) and the memory data register(MDR)
What does the control unit do?
Manage the execution of instructions, data flow inside the CPU and the input/output of the CPU.
What are the components of a computer following Von Neumann architecture?
A central processing unit containing a control unit and an arithmetic logic unit
A primary memory storing data and instructions
A clock
A cache storing frequently used instructions
What is a bus?
A high-speed internal connection
What is the address bus?
A bus that carries memory addresses from the CPU to other components(e.g. the memory, input/output devices)
What is the data bus?
A bus that carries data to and fro the CPU, the primary memory and input/output devices
What is the control bus?
A bus that carries instructions from the control unit to the components of the CPU, the memory and input/output devices.
Outline the fetch step of the fetch-decode-execute cycle.
The PC holds the memory address of the next instruction to be carried out. It is copied into the MAR.
The memory address sent along the address bus to the memory. The data represented by the memory address comes back along the data bus and is placed in the MDR, which then copies it into the CIR. The instruction is finally copied over into the control unit.
The PC is then incremented by a signal from the control unit.
Outline the decode step of the fetch-decode-execute cycle.
The control unit decodes the instruction it receives.
Outline the execute step of the execute cycle.
The control unit executes the instruction it receives, making use of the ALU and ACC if needed.
What would an increase in clock speed do?
Increase the frequency at which the FDE cycle is carried out.
What are the three types of secondary storage?
Optical storage, magnetic storage, solid-state storage
How does optical storage work?
A laser burns little holes into the surface of a disc. These holes are called pits and represent 0s in binary. Light is reflected off the surface of the disc, and detected by a sensor.
How does magnetic storage work?
An electromagnet magnetises parts of a magnetic substance as north and south poles to represent 1s and 0s.
How does solid state storage work?
Solid state technology works by using a large electric current to force electrons through a barrier, trapping them in positions called “pools”. A full pool represents a 0 and an empty pool represents a 1.
Name an example of optical storage
CDs, DVDs, Blu-ray discs
Name an example of magnetic storage
Floppy discs, hard-disc drives
Name an example of solid-state storage
Flash drives
What are the advantages of optical storage
Portability, affordability and resistance to interference
What are the advantages of magnetic storage
High capacity
What are the advantages of solid state storage
No moving parts, portability, fast read/write speeds
What are processes?
Programs in the memory waiting to be executed
What is multitasking?
The ability to run multiple processes at the same time
What is a scheduling algorithm?
An algorithm that assigns the CPU’s resources to perform tasks
Name the three types of scheduling algorithm at GCSE
Queue/FIFO, Shortest job first, Round robin.
How does the OS allocate space?
Files are broken into blocks. They are more or less equal to the sector size of the hard drive.
Blocks are placed into sectors; a sector can only have one block at a time. If the sector is not filled, space is wasted.
What is the ceiling function?
A function that rounds a number to the next integer.
What are the different operations that can be carried out on files?
Create, save, edit, open, delete, rename
What are the four access permissions?
Read, Write, Execute and Delete
What is a peripheral device?
Additional hardware connected to the computer itself.
What are drivers?
Specialised pieces of software that provide an interface between the device and the operating system, so that they may interact.
What is the user interface?
The boundary between the user and the operating system.
What are the two types of user interface?
GUI(Guided user interface), CLI(Command line interface)
What is access control?
Identifying a user based off of their credentials and authorising the appropiate level of access to the computer once they are authenticated.
What is authentication?
Proving one is the account holder.
Describe some methods of authentication
User/password, biometric, one-off passcodes
What are the four types of utility software?
File repair, compression, disk defragmentation, backup
What is the purpose of file repair?
To restore damaged or corrupted files to functionality.
What is the purpose of compression software?
To reduce file size to save space or for a transmission.
What is the purpose of disk defragmentation?
To reduce the time it takes to access files and free up larger blocks of contiguous space.
What is the purpose of backup software?
To save a copy of the system in another place in case of hardware failure or attack.
What is application software?
Software that the user directly interacts with to perform functions.
What is utility software?
Software that performs specific tasks to enhance productivity or efficiency of a computer system.
What is the operating system?
System software that manages other pieces of software and provides a platform where the user can interact with software
What is a variable?
A named location in computer memory containing a changeable value
What is a constant?
A named location in computer memory containing a value that cannot be changed.
What is an array?
A collection of data all of the same type.
What is a record?
A collection of data of different types.
What are the data types at GCSE?
String, float, integer, boolean, character
What is a string?
One or more alphanumeric characters
What is a float?
A decimal number
What is an integer?
a whole number
What is a boolean?
true/false
What is a character?
A single alphanumeric character
