Basic hardware categories, include: input (keyboard, mouse, microphones, ect.) processing (CPU, RAM, video cards, ect.), output (user interface screen, printers, speakers, ect.), and storage (external drives, USB, DVDs, ect.).
Binary digits (bits) are
- Used to represent data
- Bit is either 0 or 1
Sizing Computer Data
- 8-bit chunk equals 1 byte
- Size of main memory and storage devices
How does a computer work?
CPU (central processing unit)
- Transfers program/data from disk to main memory
- Moves instruction from main memory via data channel or bus (keeps frequently used instructions)
- Small amount of fast memory called cache (larger cache, faster but expensive)
- Contains program instructions
- Contains operating system (OS) instructions
Cache and main memory are ‘volatile’ (content lost when power is cut), while Magnetic and optical disks are ‘non-volatile’ (content saved when power is cut).
Operating system (OS)
- 4 main OS are Windows, Mac OS, Unix, and Linux
- Program that controls computer’s resources
- Large, complex program that controls computer’s resources
- Functions: read/write data, allocate main memory; perform memory swapping, start and stop programs; respond to error conditions, facilitate backup and recovery; create and manage user interface.
- Run only on particular types of hardware
- Must conform to instruction set of CPU
Memory swapping: when the main memory is too small (resulting in slow processing many programs or large files) to hold all programs and data, CPU loads programs from memory in chunks:
- Places new program into unused memory
- If none available, the operating system will remove chunk being used and replace with requested data
- It slows down the computer processing time
- Expressed in hertz (Hz)
- Classified as 32-bit or 64-bit
Needs more CPU if handling large spreadsheets or database files (such as client computers, for web, email, database, ect.) Dual processors for PCs or quad processors for servers. Servers provide service to clients (Faster, larger, more powerful, and simple video display, if any).
- Large collection of coordinated servers
- Receive and process 100s or 1000s of service requests/minute
The sever (email, ect.) -> internet (public/private) -> client
- Network of computers operating as one computer
- Companies lease time on grid
- E.g. Used for intensive arithmetic computing
- Computing network on the internet, e.g. Facebook
- Form of hardware/software leasing
- Firms get server resources from vendors who specialise in server processing
- Server time and resources leased are flexible and can change dynamically/dramatically
- Pay only for resources used
- Multiple organisations use same computing infrastructure
- Works as cloud vendors harness power of virtualisation (multiple operating systems share same hardware)
- Its design determines whether the client, the server, or both, process it
- Written to use particular operating system
- Programs perform specific user tasks/business function
- General purpose (Excel), Specific purpose (Quickbooks)
- Categories: Horizontal-market application software (provides capabilities common across all organisations and industries, off-shelf software, e.g. Excel); Vertical-market application software (serves the needs of a specific community, altered/customised by vendor or qualified consultant, e.g. tracking system); One-of-a-kind application software (for specific need, e.g. ATO taxes); Dual category software (CRM software for large customer base, configured/customised).
- Software acquired (i) Off the shelf, (ii) Off the shelf with alterations, (iii) Custom-application software (developed in-house or outside developer, risky/difficult last resort, and unique competitive advantage.
Client-server applications require processing on both client and server, thin preferred to thick clients?
Thin client (no installation/administration of client software e.g. shopping trolley, client OS not a complication, and only requires browser)
Thick client (installation/administration of client software e.g. Excel, more features on client computer, and expensive maintenance for new versions.
Open-source movement: Richard Matthew Stallman, father of movement, 1983, developed a set of tools for creating a free Unix-like operating system. GNU general public licence (GPL) agreement. Linus Torvalds, 1991, used Stallman’s tools to write Linux.
Open-source projects include: Open Office, Firefox, Apache, and Android.
Open-source software, e.g. Linux, MySQL
- Source code (human readable) made available, usually without charge
- Additions/amendments made by anyone with skills
- Provided to community for others
- Software developers not paid for work
Closed-source software, e.g. Microsoft Office: Only machine-readable code provided, original developer can make changes, depends on license sales.
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