cs paper 1

What are the 4 types of system change?

1. Direct Changeover: old system stopped, new started

2. Parallel: old and new run simultaneously

3. Pilot: system is tested on few people, bugs fixed

4. Phased: introduced in phases, old system slowly phased out

5 types of testing

1. Alpha testing: early development (internal)

2. Beta testing: testing with users

3. User acceptance: testing with audience, final check

4. Dynamic testing: making sure the output is right while code runs

5. Debugging: finding and resolving bugs

Data loss examples and how to prevent data loss

Examples: user error, malicious actions, virus, hardware malfunction, natural disasters

Prevent data loss: failover systems (systems that take over if one fails), data replication/backups, offsite, online storage

FDE cycle/machine cycle

1. Fetch: cpu retrieves instructions from pc

2. Decode: cpu interprets the instructions

3. Execute: cpu carries out the instructions, stores the result

cpu parts and their functions

• ALU (Arithmetic Logic Unit): performs arithmetic and logical operations

• Registers: supply operations to the ALU

• CU (control unit): Fetches instructions from memory, directs ALU operations

Types of memory and their functions

1. Primary memory/RAM: temporarily stores data and instructions to cpu, data is lost when turned off

2. ROM (read only memory): used to store permanent instructions like BIOS, setup instructions

3. cache: stores frequently used data so the cpu can access it quicker, L1 fastest, smallest, L2: slower, bigger

4. Secondary memory: additional storage facility added to computer

5. virtual storage: when ram is full, it’s sent to secondary temporarily

operating system and its roles

OS-a software that manages a computer’s hardware activities and resources

5 roles:

1. User interface: user interaction with computer

   • CLI (command lien interface): user type commands

   • GUI (graphical line interface): user clicks icons, buttons, menus

2. Memory management: keep track of storage, organize data, ram usage, virtual memory

   • paging: splits memory into pages and moves them between ram and storage

   • swapping: moves programs between ram storage

   • =both free up space so programs can run even if there isn’t enough storage

3. Multitasking: cpu usage distributed based on priority and time, each program gets a turn

   • interrupts: signal to cpu that an important event needs attention

   • polling: checking device in regular intervals

   • scheduling/time slicing: assigns task for cpu (depending on fcfs, importance)

4. Peripheral management: handles device drivers, bios

5. Security: user, file permissions

dedicated os: designed to run on a specific device

what is the internet and how is data sent/received

global network system, hosts www pages

packet switching: to send/receive data is split into packets, they take different routes but reach the same destination and are reassembled

what are networks and what are the types

systems that connect two or more computers or devices so they can share information, resources, and services

1. LAN (Local Area Network): connects devices in a small area, single building <1km

2. WAN (Wide Area Network): many LANs connected together over long distances, ex. internet, cellular

3. VLAN (Virtual Local Area Network): type of LAN, divides network into separate segments, reducing congestion, increasing security

4. WLAN (Wireless Local Area Network): devices connected using waves, a type of LAN, ex. wifi

5. SAN (Storage Area Network): network of storage devices, LAN type

6. PAN (Personal Area Network): connects to a users device, hotspot, bluetooth

7. P2P: 2 or more computers share data, no central point-each acts as a server and client

8. VPN: type of WAN, connection encrypted, using tunneling to hide IP

intranet vs extranet

Types of private networks

intranet: private network using www

extranet: intranet, but accessible to external parties using a portal

protocols and OSI model

Role of protocols: set of rules for data transmission

• maintain flow integrity

• prevent deadlock and errors

• flow control

OSI model: theoretical model of how data moves through a network

• 7 layers: media layers: 1-3 (hardware part) host layers: 4-7 (software part)

what is encryption and types

Encryption: encodes data, involves a key, can be read by sender and receiver only, prevent man in the middle attacks

Types:

1. WEP (wired equivalent privacy): hexadecimal password-insecure

2. WPA (wifi protected access): older method, vulnerable to some attacks

3. PSK (pre-shared key): common for securing wireless networks

4. User ID: username+password

MAC address (Media Access Control): used to identify devices, can control which devices are allowed on network

Firewalls: controls incoming and outgoing traffic by analyzing data packets

algorithmic thinking types of searches and sortings

algorithm: set of steps used to complete a task

Type of searches:

1. Sequential search: checks every item one by one

   • good for small data sets, inefficient for big

2. Binary search: divides the list in half and compares the target with the middle element

   • on sorted lists

Types of sorting:

1. Bubble sort: swaps pairs until list is sorted

2. Selection sort: simplest way to sort from low to high

HLL and types of translators

HLL (Higher Level Language): needed because low level or machine can take long and are hard to understand, closer to human thinking

Types of translators:

1. Compiler: translates high-level code into machine code before it’s run

2. Interpreter: translates high-level code line by line at runtime

3. Assembler: converts assembly code into machine code

virtual machine: runs programs anywhere or runs OS inside your main one

static vs dynamic data structures + types

static: size, memory fixed during execution-arrays

dynamic: size can change during execution, allows for flexible memory allocation-linked lists, trees

Types:

1. Arrays: matrix used to store data

2. Stacks: LIFO data structures, push: add new at the end, pop: remove the last

   • ex. back button, undo key, browser history

3. Queues: FIFO data structure, enqueue: add at the back, dequeue: remove at front

   • ex. print jobs, task in CPU

4. Linked lists: data structure made up of nodes, where each node contains data and a link, singly, doubly, circular, circular doubly

5. Trees: each node contains data, left and right child

   • breadth first, pre-order, in-order, post-order

what is bandwidth and what are computer types

Bandwidth: max amount of data that can be transmitted over a network

types of computers:

1. Mainframes: one big computer, many processors, used for reservation systems, weather prediction

2. Server Farms: many computers, servers linked together, used for data centers, cloud hosting

Control system components, types of feedback

Control systems: A device that manages behavior of other devices

Components:

• microprocessor: chip containing CPU functions

• sensor: detects or measures physical properties

• actuator: converts inout signal to move something physical

• transducer: converts one form of energy to another using sensor and actuator

Feedback: out put is returned as input to help systems adjust, improve

1. Open loop system: Doesn’t take feedback into account ex. TV remote, toaster

2. Closed loop system: Adjusts based on output

• Negative feedback loop: reduces fluctuation, stabilizes (ex. airplane)

• Positive feedback loop: amplifies fluctuation (ex. speaker amp)

div and mod

div: division keeping only whole number part

• ex. 7 div 3 = 2

mod: remainder after division

• ex. 7 mod 3 = 1