System Fundamentals

System Fundamentals

• New systems are needed when old systems are inefficient, outdated, or unsuitable.
• A new system can increase productivity, improve quality, and minimise costs.
• The extent of a new system update is determined by time, software, hardware, personnel, and environment required.
• Implementing a new system might require training, firing employees, acquiring more hardware, and changing the server location.
• Project viability is determined via consideration of compatibility, mergers, data migration, hosting, and installation issues.
• Technical feasibility: Determines if technology is advanced enough.
• Economic feasibility: Determines if the new system is cost-effective and if there are sufficient funds.
• Legal feasibility: Determines if there are conflicts between the system and laws/regulations.
• Operational feasibility: Determines if existing organizational procedures support maintenance and system operation.
• Schedule feasibility: Determines the time it will take to implement.
• Change management involves shifting people/departments/organizations to the desired state.
• Maximising benefits and minimising impacts results in stakeholder acceptance.
• Plan the system to resolve issues and inform users of features.

Compatibility Issues

• Compatibility issues may arise from business mergers involving incompatible systems.
• Communication issues and different interpretations due to language differences cause incompatibilities.
• Software incompatibility occurs when different software/systems cannot operate on the same computer/network.
• Legacy systems: Use of old tech (hardware/software/computer systems/programs) is continued if sufficient, data conversion is impossible or applications cannot be upgraded.
• Strategies for merging include keeping both systems, replacing both, or combining the best of both.

Using Client Hardware vs Hosting Systems Remotely

• Locally hosted systems: Software is installed and operated on client's hardware/infrastructure.
• This amounts to buying the software package and owning it.
• Best for large, complex systems.
• Only pay once, excluding maintenance costs.
• Control data in secure data centre, less risk of data loss.
• Remote hosted systems: A Software as a Service (SaaS) solution, where hardware is elsewhere and centrally updated.
• Users can access data and operate software from the cloud, paying via subscription.
• Lower initial cost.
• It is easier to predict the overall cost.
• Excellent if the organisation lacks hardware.
• Don't have to maintain the software yourself.
• Data is secured within a data centre.
• Third-party reliance introduces risk of data loss or provider shutdown.
• Legislation may be weaker in another country.
• Generally has lower performance than on-premise solutions.
• Time zone differences and internet dependency can cause inconvenience.

Installation Processes

• Implementation/conversion involves online and retiring systems.
• Parallel installation means both systems run parallel to each other to compare outputs until satisfied and terminating old one.
• If the new system fails, can revert to old one, lower risk and ideal for critical systems.
• Higher cost and inefficient if systems have different input/outputs/ process.
• Direct/Big Bang installation means setting up and terminating old systems at the same time.
• It is preferred if the system is not critical.
• Riskier, but less costly.
• Pilot installation means introducing the new system in one of the sites (pilot site/group) then introduced to others if successful.
• Less risk, but requires worker training
• Phased installation means converting one module at a time.
• Requires training and a longer implementation period.

Problems with Data Migration

• Data migration involves transferring data between formats/storage types/computer systems when switching/changing/upgrading/merging.
• File format incompatibility in the new system could result in incomplete or incorrect data transfer.
• Non-recognizable data structures, formats result in data mismatch in locations.
• Data can be lost/corrupted during transmission due to faults/lack of adequate storage.
• Data misinterpretation occurs due to conventions in different countries, e.g., date, measurements, currencies.
• Different validation rules between companies can lead to inconsistent/incorrect results.
• Data might not be usable during the transferring process, especially if large.

Types of Testing

• Testing identifies problems/areas for improvement and if a system/software meets requirements.
• If not done properly, the system is inadequate with issues like low productivity and increased costs.
• Alpha testing involves offering an early development version to developers for feedback.
• Beta testing involves providing a version to a select group/the public for real-world feedback.
• The user report is not always of the best quality in this case.
• User acceptance testing is the last stage, to ensure the product satisfies its target audience.
• Debugging involves systematically finding and correcting bugs/errors.
• Some programs do it automatically and faster/cheaper.

User Focus

• User documentation helps users understand/use the system, allows them to quickly adapt to software/system, improves efficiency.
• Documentation includes requirements (attributes, characteristics, functions), technical details(installation and configure), end-user manuals(support staff and system administrators details), marketing(how to market, analysis of market demand).
• Documentation methods include cheap/accessible help files, online documentation, and manuals.
• Online documentation has easier searchability, can be updated, but has limited internet access.
• Manuals are accessible any time regardless of internet access/installation status, but cannot be updated.

User Training

• Self-instruction uses resources to learn (manuals, websites, etc.) and are easy/cheap/flexible.
• Formal classes involve classroom settings with free discussion.
• Remote/online training has a variety of courses, is cheap/easy to set up.
• Skills may not be as effective.
• In general, new systems are implemented faster to reduce costs and minimise inefficiencies.

System Backup

• Data loss can occur due to user error (accidental deletion), natural disasters, malicious activities, computer viruses, and power failure.
• Consequences include lives at risk (hospital), financial loss, damaged reputation.
• Regular backups are on disks/magnetic tape/online or removable media for fast backup and storage.
• Offsite storage means backups are stored in different geographical locations.
• Firewalls protect against viruses.
• Failover systems switch in case of hardware/software/network failure.

Software Deployment

• Users install updates to fix bugs/errors and benefit from improvements.
• Organizations with different locations can face incompatibility from different versions.
• Patches fix known bugs and vulnerabilities, but may introduce new ones.
• Updates fix bugs and have minor functionalities.
• Upgrades fix bugs with new major functionalities/characteristics which require additional payment.
• Releases are final, working applications that are gone through testing.
• Cookie alerts user on software installs.
• Email alerts user by sending registered user a download link.

Computer Components

• Hardware comprises physical, tangible elements (CPU, HDD).
• Software is a set of instructions for the CPU.
• Peripheral devices connect to and communicate/work with the computer.
• Human resources make up the workforce of an organization/business sector/economy.
• The human resources function is sometimes combined into software.
• A client piece of computer hardware/software that accesses services available by server, by sending requests to server.
• A server hosts computers that fulfill requests over the network and shares information.
• An email server transfers messages from one computer to another in a network.
• A DNS translates web addresses to numeric IP addresses.
• A router connects networks and forwards data packets between networks, deciding on forwarding.
• A firewall controls network data traffic based on a preset of rules, necessary to protect integrity.

Ethical/Social Issues

• Security: Protecting hardware, software, peripherals, data, and networks from unauthorized access.
• Privacy: Controlling data access and usage, protecting ID, but anonymity raises cyber bullying issues.
• Censorship: some information may be inappropriate, network managers block websites.
• People and machines: Easier communication, more efficiency, but can cause addiction, real-life neglect, lack of sleep, health issues.
• The digital divide causes inequality regarding computer system use/access, leading to unequal information and education access.
• Surveillance involves monitoring people for enforcement/traffic control and causes ethical privacy concerns.
• Globalization/cultural diversity spreads information, reduces boundaries, and diminishes traditional culture.

Practical Issues

• Reliability indicates consistent function, minimal failure to avoid data/time/revenue loss, injury, etc.
• Data integrity & consistency requires complete, up-to-date unaltered data.
• Standards/protocols: Rules include industry/proprietary standards.

System Design and Analysis

• Stakeholders have an interest/investment in a project.
• System analysts collaborate with stakeholders (clients/end-users).

Obtaining Requirements

• Interviews: Face-to-face conversations that are structured/unstructured.
• Questionnaires: Can be closed/restricted (yes/no, box checking) or open/unrestricted (free response questions)
• Direct observation of current procedures

Evaluating Requirements

Interviews:

• Talk directly to users, observes non-verbal behaviour = more reliable, valid data
• Unstructured interviews can reveal more questions, detailed reports
• Data is harder to summarise/evaluate/analyse
• Detail depends on interview type, structured interviews less useful
• Time consuming to get detailed results

Questionnaire:

• Time/cost efficient to get info from large groups
• Closed questions easy to compare
• Open questions= more detailed reports
• Detail depends on question type, closed questions don't give opportunity for clarification
• Stakeholder misunderstanding can invalidate answers

Observations:

• Highlights aspects, more detailed reports

• More reliable than interviews because see people in reality

• Time/expensive, need to observe cycle

• People act differently if watched = unreliable

• A prototype is an early sample/model to test and gather feedback, allowing clients to follow development and see changes.

• Iteration (iterative design): Solutions/prototypes are designed, developed, tested and evaluated in repeated cycles to add features until fully functional.

• Failure to involve user in the design process limits feedback, and adversely affects productivity and efficiency.

• Flowcharts show flow of data through the program.

• Data Flow Diagrams display data storage and movement.

Usability

• Usability: The ability to accomplish user goals making the application more efficient and quick to learn.
• Accessibility: The ability of system/ device to meet needs of individuals.

Usability Problems and Examples

• Learnability refers to ease of accomplishing basic tasks for first-time users.
• Efficiency refers to how quickly users can perform tasks.
• Memorability refers to how easily users can establish proficiency after not using it for a period.
• Error refers to how many errors, the severity, and how easily users can recover.
• Satisfaction refers to how pleasant it is to use the design.
• All these things are affected by complexity/ simplicity, readability/ comprehensibility, or other factors.
• Usability issues with mobile devices include size of the screen, size of keys, and battery life.
• Accessibility/usability problems can be solved for disability or impairment.

Solving Accessibility/Usability Problems

• Visual impairment uses braille, speech recognition, color changers and magnifiers.
• Hearing and speech uses subtitles and visual effects.
• Cognitive problems use word processors.
• Mobility uses eye typer, puff and suck switch, foot mouse, speech recognition.

Computer Organisation

• Computer architecture: Central Processing Unit (CPU): Component of a computer system which interprets/ processes and executes program instructions.
• Control Unit (CU): Fetches data/ instructions from memory, decodes it into commands and controls transfer of data/instructions among other units of CPU.
• Arithmetic Logic Unit (ALU): Performs arithmetic and logical calculations/operation
• Registers: Small, very fast circuits that store intermediate values from calculations or instructions inside the CPU
• Memory Address Register (MAR): Stores address of next instruction to be decoded and executed, Connected to RAM through Address Bus
• Memory Data Register (MDR): Stores data of instruction most recently taken from RAM, i.e. instruction about to be executed. Connected to RAM through Data Bus

Instruction/Machine Cycle

• The basic operation cycle of computer taking place within certain time period is where instruction is fetched, decoded, executed and stored.
• Addresses of instructions are stored in MAR (through Address Bus)
• Using location, data is stored in MDR
• CU decodes the instruction
• ALU executes the command
• Output value is stored in accumulator if needed
• Processed data stores back in main memory.

Storage

• Primary: Storage directly accessible by CPU eg RAM

• Secondary: "Auxillary storage that is slow but high capacity

• Random Access Memory (RAM): Stores data and instructions currently being run.

• Volatile, data instructions deleted once there's no power.

• Read Only Memory (ROM): Stores permanent instructions and data of programs used for boot and operation and are non-volatile.

• Cache memory: Memory type smaller and faster than RAM, stores data and instructions the CPU accesses.

• Secondary memory: Relatively slow with a higher capacity than primary memory, non-volatile.

• Data and instructions copied from secondary storage to RAM before being executed by CPU.

• Virtual memory: Uses part of secondary memory as if main memory.

Operating and Application Systems

• Operating system: Software set that controls hardware resources and provides services for programs.
• Roles of an Operating System:
• Peripheral communication: Provides hardware interface for applications.
• Memory management: OS allocates memory sections in each process.
• Data management: Provides accessible and reliable data.
• Resource allocation: Time sharing, and memory management.
• Security: Provides access measures for safety, logs activity.
• Application software: eg, Word processing, spread sheets, database management systems, web browser, email, CAD, graphic processing etc.
• The graphical User Interface or GUI allows user to interact with CLI; this includes toolbars, menus and dialogue boxes.

Binary

• Represent info through 1s and 0s
• Positional systems include binary, decimal, hexadecimal
• 104(base 10) is decimal, 84(base16) is hexadecimal

Data Representation

• Integers: 265 values represented by 8 digit numbers
• Characters: Standard Code for Information Interchange (ASCII) encodes characters
• Strings: eg UTF-8 codes
• Colors: Through hex pixels that represents red green blue

Logic Gates

• AND gate: will output TRUE only if inputs 1 and 2 are TRUE

• OR gate: will output TRUE if either inputs, input 1 or inpt 2, is true

• NOT gate: output is the inverse of the input

• NAND : NOT AND gate; the output is inverted, so when both inputs are TRUE, output is FALSE

• NOR : NOT OR gate; opposite of gate.

• XOR if either input true, output = TRUE. Except for when both inputs = TRUE, then output = FALSE.