Comp Sci Exam 1 2025

What does a computer system consist of?

A computer system consists of hardware, software, people working with it or using it, and the immediate environment. 

What are some methods of data gathering?

Interview (structure/unstructured), questionnaire(open/closed), document collections and observations.

What are the 4 types of cloud computing?

IaaS – Infrastructure as a Service (raw computing power)

PaaS – Platform as a Service (frameworks for developers)

SaaS – Software as a Service (e.g. Kognity, ManageBac) (hosted online apps like Google Docs)

NaaS – Network as a Service (virtual networking services)

Advantages of SaaS

Low initial cost and requires few investments in installation, maintenance, and upgrading.

Can be scaled dynamically. (e.g. It can be used in a 10 people workshop, or it can be scaled up to a 1000 people school)

Disadvantages of SaaS

Slow performance - depends on internet

Data loss risk

Hard to integrate with other solutions is hard 

Legacy Systems: Meaning, Reasons for use, Risks.

• Old technology, hardware, computer system, or application program still in use

• Used because:

  • Can’t convert data to newer formats

  • Can’t upgrade application

• Risks:

  • Incompatible

  • High maintenance cost

  • Security issues (easily exploited)

Outdated web server. (e.g. IIS 4.0)

Outdated operating system (e.g. Windows XP)

Outdated web browsers (e.g. IE 6)

On-Premise (Local) Software

On-premises software is installed and runs on computers on the premises of the person or organization using the software, rather than at a remote facility such as a server farm or cloud.

Pros: Security, Backups can be controlled, Legacy software, Software+Feature control

Cons: Cost of hardware, Technical support, Lack of collaboration. 

Changeover

Changeover: In organizations, sometimes we changeover our systems. It is the process of putting the new system online and retiring old ones.

Choice of implementation (conversion, changeover) method includes following four methods:

Parallel: Both systems work in parallel for a short period of time. 

Pros: low risk 

Cons: training period is extended, adoption of new system takes longer, higher cost due to the maintenance of two separate systems 

 

Direct (immediate/Big bang): Plugs in new system and unplugs the old one at the same time. 

Pros: less cost 

Cons: risky, dangerous when new one is not working,  need to be trained properly 

 

Pilot: New system is introduced in one of the sites and extended to other sites over time. 

Pros: low risk, pilot sites serve as models for the rest 

Cons: only work with multiple sites 

 

Phased: Converts one module of the system at a time. 

Pros: low risk 

Cons: Training period is extended, Adoption of new system takes longer 

Data Migration

🔁 Data Migration

• Moving data between formats/systems

Risks:

• Data loss: Data may be lost or not transferred due to incomplete data transfer or errors during the process. 

• Security: ensure all the data is securely encrypted before migration 

• Compatibility: Incapability of moving the information due to parameters such as incompatibility. Data may also be misinterpreted due to incompatibilities. e.g. Change OS and unexpected file formats 

• Long Transfer Times: Connection speed or hardware restrictions 

• Unexpected Higher Cost: improper planning  

Testing Types

Alpha Testing is done before the software product is made available to the general public. (Labratory - Developers) 

Beta Testing includes comments and suggestions of the users. Unlike Alpha testing, users outside the company are involved in the testing. Their feedback is valuable and can be used to fix defects anderrors that were missed.

Black-box: Tests inputs/outputs, not code

White-box: Tests with access to internal code

User acceptance testing: Testing any new/updated system with its ultimate end users to see if it meets their expectation is very important.

User Documentation

A user documentation usually involves: 

• Minimum hardware and software requirements 

• Installation guide 

• How to start the system 

• How to use different features of the system 

• Screenshots explaining main features of the system 

• Example inputs and outputs 

• Explanations of error messages and troubleshooting guides 

• Information to contact the developer of the system if an undocumented question arises 

Methods of Delivering User Training

• Self-instruction: Users read a manual or watch a tutorial, or randomly do something in the system to figure out how it works. This type of training is only suitable for experienced computer users.

• Formal classes: Users sit in a classroom, listen to an instructor who shows and explains how to use the system. This type of training is useful to train large amounts of staff as it is effective and relatively cheap, but if the size of the classes is too big, there is little time to deal with individual problems and questions.  

• Remote/Online training: An instructor trains a single user either by being in the same room or by some kind of remote connection (Skype, chat). This is the most effective way of training as it can be suited to user's needs and abilities but is very expensive compared to other. 

Common Causes of Data loss

• Human Error 

• Viruses & Malware 

• Hard Drive Damage 

• Power Outages 

• Computer Theft 

• Liquid Damage 

• Disasters 

• Software Corruption 

• Hard Drive Formatting 

• Hackers and Insiders 

• Software and Development 

Data Loss prevention techniques

Back up: By copying all sensitive information on to a different medium than the one used in the system, like a second hard disk or CDs, chance or information loss can be reduced significantly. By storing these media physically separated from the system, data loss due to malicious activities can be prevented as well.

Hard Copies: In some cases, information can also be printed out to be archived, like books, texts, important contracts or scientific papers. However creating hard copies can be expensive and take up a large amount space. Hard copies are also liable to data loss, as in the case of print outs getting burned in fire

Strategies for managing releases and updates 

Automatic updates: The system checks automatically for updates over the internet from time to time. If updates are available, they are downloaded and installed automatically. 

Advantages: 

• Updates get installed automatically. Inexperienced users have an easy chance to get the updates. 

• No need for software manufacturer to contact every user about the new software. 

Disadvantages: 

• Users miss updates if they are not connected to the internet. 

• If updates bring a major change of system functions, users might not be informed about it. 

 

Manual update: The software manufacturer contacts every user about the new update and supplies the installation package to him to be installed. 

Advantages: 

• Users have more control what updates they want to install 

• Users get to know if an update brings major changes to how the system works 

Disadvantages: 

• Users might miss an update fixing security issues 

• Users might not know how to install the update 

• Users might harm system by wrongly installing update 

• Users might lose medium containing the update 

Prototype

Prototypes are abstract representations of the system, often focusing on only one or two key aspects of the system. They are important in testing as each component of the system can be tested before implementing, and to illustrate the working of the future system to the client. (early versions of the system)

Benefits: 

• Attracts the attention of the client, since it encourages them to use it and "get a feel for it“ 

• Provides just enough of the concept for the investors to decide if they want to fund the full production or not 

• Encourages active participation between users and developers 

• Gives an idea of the final product 

• Helps in the identification of problems with the efficiency or the design 

• Increases system development speed 

 

Accessability

Accessibility refers to the potential of a service, product, device or environment to serve and meet the needs of as many individuals as possible.  

A system characterized by high accessibility can meet the needs of many people, while a system with low accessibility presents barriers to specific groups of people. 

Frequently, accessibility is studied in parallel with disabled people (people with special needs) and the use of various assistive technologies. 

 

Types of Processing

Ergonomics

designing and arranging things people use for users to interact most efficiently and safely.

Usability

Usability refers to the potential of a product, application or website to accomplish user goals.  

Usability relates to effectiveness, efficiency and satisfaction in a specified context of use. 

Usability is the property of a system that determines how easy and  self-explanatory the use of the system is for unexperienced end-users. It usually measures ergonomics and accessibility of the system. 

Methods that can be used to improve the accessibility of systems

• Touch screens 

• Voice recognition 

• Text-to-speech 

• Braille keyboards 

• Braille printers 

• Simpler interface with fewer buttons 

Common Usability Issues

• Complex navigation

• Poor feedback

• Inconsistent design

• High cognitive load

• Bad error messages

• No accessibility

• Slowness / crashes

• Confusing interface

• Overcrowded design

• No help section

👉 All People Seem To Need Data Processing

That’s the 7 layers, in order:

1. Application

2. Presentation

3. Session

4. Transport

5. Network

6. Data Link

7. Physical

Why layers matter:

• Easier to manage

• Manufacturers can make compatible stuff

• Tech updates can happen in one layer without breaking others

5. Protocols (Communication Rules)

What is a protocol?
A set of rules that governs:

• What is sent

• How it’s sent

• When it’s sent

Examples to memorize:

• TCP: Sends data reliably (e.g. websites)

• FTP: File Transfer Protocol

• SMTP: Email sending

3. Types of Networks

Just know these terms and what they stand for:

• LAN: Local area (e.g. school)

• WLAN: Wireless LAN

• VLAN: Virtual LAN — divides network virtually

• WAN: Wide Area (e.g. internet)

• SAN: Storage network

• VPN: Secure connection over internet

• PAN: Personal (e.g. Bluetooth earbuds)

• P2P: Peer-to-peer (no central server)

A hub consists of multiple ports. When a network device wishes to send data to some other device on the network, it sends the data to the hub. The hub then copies the data and sends it to all devices connected to its ports. The device waiting to receive the data accepts the data. All the other devices just ignore it. 

A switch is also the connection point for multiple devices on a single network. However, unlike a hub, the switch can identify which network device is connected to which part. This allows the switch to transmit data to the exact port and network device for which it is intended. 

Router is a more sophisticated device than both a hub and a switch. Its use is to join multiple networks and serve as an intermediary between these networks so that data can be exchanged effectively and efficiently between network devices of those networks.