Computer Science Summer Mock

explain the term algorithm

a sequence of steps that can be followed to complete a task

explain the term decomposition

breaking a problem into a number of sub-problems which might itself be further subdivided

explain the term abstraction

the process of removing unnecessary detail from a problem

Describe the steps a linear search would follow

• Starting with the first value

• Checking all values in order

Describe the steps a binary search will follow to look for a number in a sorted list

• Select middle number (or left of middle as even number)

• check if selected number matches target number

• if searched number is larger, discard left half // if searched number is smaller, discard right half

• Repeat until number found or remaining list is of size 1 (number not found)

For Binary Search numbers must be ….

ordered

Linear Search is better … (compared to binary search)

Faster on small datasets and simple to understand

Linear Search is worse… (compared to binary search)

Slower on larger datasets and less efficient

Binary Search is better … (compared to linear search)

Faster on large datasets and more efficient.

Binary Search is worse… (compared to linear search)

Data must be in order and more complex to implement

merge sort is…

a sorting algorithm that divides a dataset into smaller sub-datasets and merges them back together in the correct order

bubble sort is…

a simple sorting algorithm that starts at the beginning of a dataset and checks values in 'pairs' and swaps them if they are not in the correct order

Merge sort is better… (compared to bubble sort)

Suitable for large datasets and performs well even on very unorganised data

Merge sort is worse… (compared to bubble sort)

Uses lots of memory and more complex to implement

Bubble sort is better… (compared to merge sort)

Simple to understand and implement

Bubble sort is worse… (compared to merge sort)

Slow for large datasets and inefficient

count controlled iteration code

for loops

condition controlled iteration code

while loops

selection code

if statements

subroutine

procedure or function

// name and meaning

DIV, gives whole integer of division without remainder.

%

MOD, gives remainder of division

equal to

==

not equal to

!=

greater than or equal to

>=

less than or equal to

<=

code to print uppercase, use variable name

print(name.upper())

code to print lowercase, use variable name

print(name.lower())

code to find length, use variable name

len(name)

code to find substring, use variable name find n to m

name[0:2]

concatinate Fname and Sname into variable FullName

FullName = FName + SName

code to convert ASCI letter A to numerical value and print it

print(ord("A"))

code to convert numerical value 97 to ASCII code and print it

print(chr(97))

What is casting?

converting one data type to another

import for random number generation

import random

code for random number generation of 1 to 10 with variable number

number = random.randint(1,10)

Explain the advantages of using subroutines in programs.

• Avoid duplicating code as they can be reused

• Improve the readability

What are parameters?

values that are passed into a sub program

What is a syntax error?

• an error that breaks the grammatical rules of a programming language and stops it from running

What is a logic error?

incorrect code that produces an incorrect output

What base is decimal?

10

What base is binary?

2

What base is hexadecimal?

16

Why do computers use binary?

To represent all data and instructions

Why is hexadecimal often used in computer science?

-Large numbers can be represented in fewer digits

-it is easier for humans to understand, write and check than binary.

How many columns on a nibble table?

4

How many columns on a byte table?

8

What does a small b represent?

bit

What does a big B represent?

byte

What is a bit?

fundamental unit of information

1KB/kilobyte is

1000 bytes.

1MB/megabyte is

1000 kilobytes

1GB/gigabyte is

1000 megabytes

1TB/terabyte is

1000 gigabytes

What is a character set?

A collection of characters that a computer recognises from their binary representation

What is ASCII?

a character set of 7 bit code that can hold 128 characters

What is Unicode?

a character set of 16 bit code that can hold 65,536 characters

Advantage of ASCII over Unicode

Takes up less storage

Advantage of Unicode over ASCII

Has more characters

Unicode uses the same codes as ASCII up to ...

127

What is hardware?

physical components of a computer system that you can touch

What is software?

the programs that control the hardware that cannot be physically touched

What is system software?

software that manages the computer system resources and acts as a platform to run application software

What is application software?

software that performs end-user tasks

2 Examples of application software:

social media application and gaming software

1 Example of system software:

operating systems

operating systems handle management of the:

memory, security and applications

State the purpose of an assembler:

To translate assembly language into machine code

State the purpose of an interpreter:

converts each high-level program statement into machine code and executes it line by line, helping with debugging

State the purpose of a compiler:

convert high-level code into machine code all at once, making programs run faster

Explain the role and operation of main memory

the computer's short-term storage for instructions and data that the CPU needs to access quickly

Explain the role and operation of arithmetic logic unit

performs arithmetic and logical operations and acts as a gateway between primary memory

Explain the role and operation of control unit

manages the execution of instructions by sending control signals to coordinate execution and controls FDE cycles and buses

Explain the role and operation of register

store small amounts of data that are needed during processing

Explain the role and operation of clock

to synchronise the computer's hardware components

Explain the role and operation of bus

a collection of wires through which data is transmitted from one component to another

Explain the effect of the following on the performance of the CPU:clock speed

the faster the clock speed the faster the the FDE cycles and CPU

Explain the effect of the following on the performance of the CPU:number of processor cores

the more cores the fore instructions can be processed in a given time

Explain the effect of the following on the performance of the CPU:cache size

the larger the cashe the less time the processor has to wait for instructions to be fetched

Understand and explain the Fetch-Execute cycle. FETCH

the next instruction is fetched to the CPU from main memory

Understand and explain the Fetch-Execute cycle. DECODE

the instruction is decoded to work out what it is

Understand and explain the Fetch-Execute cycle. EXECUTE

the instruction is executed

RAM

Stores programs and data currently in use

ROM

Stores start-up instructions for the computer

Cache

Stores copies of frequently used instructions to speed up execution

Register

Super fast storage of instructions, data or addresses that the CPU is working on

volatile

memory is cleared whenever the supply of power is lost

non-volatile

memory will continue to hold anything it was storing even if it is not receiving any power

Main memory

any form of memory that is directly accessible by the CPU

Secondary storage

any non-volatile storage mechanism not directly accessible by the CPU

advantages and disadvantages of solid state

portable and durable due to lack of moving parts, high cost

advantages and disadvantages of optical storage

low cost and portable as it is small, low capacity and susceptible to damage

advantages and disadvantages of magnetic storage

high capacity and low cost, data can be corrupted if exposed to strong magnetic fields

Explain the term cloud storage.

long term secondary storage of data that resides in a remote location

advantages and disadvantages of cloud storage

reliable and high capacity, inaccessable without internet and can lead to privacy concerns.

What are embedded systems?

Computers built into other devices

name 2 embedded systems

calculators and phones

name 2 non-embedded systems

computers and dedicated servers

Define what a computer network is.

two or more computers connected together for the purpose of communication

advantages and disadvantages of computer networks

communication can be made easy with emails and users can share files, increased security risk to data and malware can infiltrate the network