IB Computer Science - Exam 1 Review

CPU (Central Processing Unit)

processes and executes various instructions/programs sent by the end-user

CU (Control Unit)

controls the flow of data and regulates the processor while interpreting/decoding instructions

ALU (Arithmetic and Logic Unit)

responsible for calculation and logistic processes

Peripherals

any external device that provides input/output for the computer (ex. mouse or printer)

RAM (Random Access Memory)

volatile primary memory that temporarily holds data/results of executions connected to the CPU

HDD/SSD

secondary memory that permanently stores data

ROM (Read-Only Memory)

NONvolatile primary memory that holds data in order to boot computer and may not be modified

MAR

memory address register that holds the address of data sent to or from the RAM

MDR

memory data register that holds the data sent to or from the RAM

CPU Cycle

Fetch - instruction sent from RAM to CU Decode - instruction decoded and sent to ALU Execute - ALU executes code Store - ALU sends it to RAM for temporary storage

Clock Speed

amount of cycles per second that the CPU may execute (GHz) (hyper-threading allows for several computes at once)

Buses

physical connections btwn. components to send data/addresses/power/signals

Data Bus

sends data btwn. hardware

Control Bus

transfers control signals btwn. components to create a structure of communication

Address Bus

sends addresses to other components

System Bus

contains data/address/control buses (3 in 1)

Cache Memory

smallest yet most efficient memory that the CPU can directly access/synchronize with to improve performance

OS (operating system)

collection of programs that control the executes of software applications such as data mgmt. and I/O control

OS Security

user mgmt (password) / firewall / anti-virus / system of privileges

Bit

binary digit representing 0 or 1

Byte

8 bits (1024 bytes in 1 kilobyte)

Binary to Denary (decimal base-10)

positions from right to left calculating using 2 to the power of x (x representing position), multiplying it by the binary value and adding them all up

Binary System

base-2 system that is used in digital circuits

Hexadecimal System

base-16 system to simplify binary by representing 4-bit binary sequence, commonly used to describe colors

Binary to Hexadecimals

values above 9 in binary are representing in letters (A-F) to represent 10-15

0000 = 0 0001 = 1 .... 1001 = 9 1010 = A .... 1111 = F

Hexadecimal to Denary

positions from right, number/letter value multiplied by 16^x (x representing the position) (ex. 2A = (216^1) + (A16^0) = 42)

Decimal Values

multiply decimals by 2 till singular whole number, ones of mixed numbers used to represent 1's (1.375 (denary) = 1.011 (binary))

Denary to Hexadecimal

divide number by 16, remainder written as hexadecimal answer from right to left, keep dividing quotient till equal to 0.

650 = 28A

Direct Changeover

New System completely replaces old system in a short amount of time (ex. an entire law firm moves from one building to another in a day)

Advantages

• Cheap, Easy

• Efficient, short installation time

• Available Immediately

Disadvantages

• Compatibility Issues may arise

• No recovery available

• Employees may not like system

Parallel Changeover

New system started alongside old system and used with the same data (ex. 2 internet providers used at the same time)

Advantages

• If new system fails, old system runs backups

• Both systems may be compared to see if new system provides correct results

Disadvantages

• Takes significantly longer to do so

• Costly to keep both running

Pilot Changeover

New system tested on a small section alongside large-scale old system, once ironed out, new system will completely replace old system

Advantages

• Cost-Effective

• All features tested

• If it fails, then it will only effect a small number of people

Disadvantages

• Those in the pilot group will have a delay in work efficiency

• The pilot group may approve of the new system, but others may not

Phase Changeover

New system introduced in phases, slowly replaces old system in parts (ex. changing computers in a large school. classroom by classroom each day)

Advantages

• Allows people to get used to system

• Training of staff done in stages

Disadvantages

• 100% implementation will take much longer

Types of Data Loss

• Hardware/Systems malfunctions

• Human Error

• Software Corruption

• Malicious Software (Viruses)

• Natural Disasters

Ways to Prevent Data Loss

• Updates - fix problems found by people to prevent software corruption by fixing code, usually free

• Patches - small bits of code inserted into program for temporary fixes

• Human Error Prevention - keep liquids and magnets away, use a backup power supply (UPS), clean computers, and keep it safe from theft

• Removable Media - makes it easy to safely remove storage from computers to others

• Offsite Storage - a backup process external to an organization which is a physical copy

• Cloud Storage - backup stored on the internet which is done remotely

• Failover System - constant capability to automatically switch to a reliable backup system when the primary server fails

• Data Redundancy - same piece of data held in two separate places to offer extra layer of protection