Chapter 1 Notes: Types and Components of Computer Systems

A computer is a device that can follow a set of instructions to carry out sequences of arithmetical and logical operations.
The instructions to be followed are called a 'program'.
There are two main parts of any computer system: the hardware, and the software.
Hardware refers to the physical parts you can touch; software refers to programs and data that run on the hardware.

Internal hardware: components fixed to sockets on the system board or motherboard; connected by thin copper traces on a printed circuit board (PCB).
External hardware: peripherals connected to the computer from outside (examples listed below).
Central processing unit (CPU): the processor that interprets all instructions in programs and executes them.
Memory types: internal memory used to store program instructions and data that the processor is working on.
Dedicated expansion cards: graphics card (for the monitor), sound card (for speakers/headphones), network interface card (NIC) to connect to a network.
Storage: RAM, ROM, hard disk drives (HDD), solid state drives (SSD), optical drives.
Peripheral devices (input/output): keyboard, mouse, monitor, speakers, printer, camera.
Examples of internal hardware components include:
- CPU
- Motherboard
- Graphics card
- Sound card
- NIC
- Internal memory
- RAM
- ROM
- HDDs
- SSDs
- Optical drives
All components are fixed to sockets on the motherboard and interconnected by copper traces on the PCB (the system board).

Software controls the operations of a computer or processing of electronic data.
There are two main types of software:
- Applications software: end-user software that enables daily tasks and activities on the computer.
- System software: includes the operating system and utilities; essential to keep the computer working.

Examples and purposes:
- Word processing applications: produce letters, reports, and memos.
- Spreadsheet applications: calculations or graphs and charts.
- Database management programs: store and retrieve information.
- Presentation applications: create slide shows.
- Graphics editing software: create artwork or edit photos from a digital camera or scanned image.
- Video editing software: produce and edit videos.
- Computer aided design (CAD) packages: produce detailed technical designs and plans.
Audio and communications:
- Audio production and editing programs: high-quality music production and editing.
- Communications software (browser and email): access the internet and send/receive email.
Other app types:
- Control software: used to control devices such as fire alarms and mechanical devices.
- Measurement software: used to capture and log data from sensors (e.g., temperature, pressure, light intensity).
- App (short for application): a small program that can perform one or a few simple tasks, usually on mobile devices.
- Applet: an even smaller program that performs a single simple task.

System software includes program/software that allows the hardware to run properly and enables communication with the computer; it includes utilities and the operating system.
Without system software, a user has no starting point for giving the computer instructions.
Major components:
- Compilers: translate high-level language into machine code.
- Linkers: take one or more object files produced by a compiler and combine them into a single runnable program.
- Device drivers: software that controls a specific hardware device; without drivers, hardware (e.g., printers) cannot work with the computer.
- Operating system: collection of programs that manage resources and run applications.
- Utilities: designed to carry out specific tasks (e.g., creating folders, copying files, antivirus, disk repair, file management, disk defragmenter).

Analogue data: a continuous signal representing physical measurements that change over time; denoted by sine waves.
- Examples: sound waves from speech (human voice), sensor data, analog electronic devices.
Digital data: discrete time signals generated by digital modulation in binary form; denoted by square waves.
- Examples: software, documents/files, computers, CDs, DVDs, and other digital devices.

Analogue:
- Values change smoothly and gradually.
- Quality can be lost during storage/transmission.
- Needs to be converted to digital to be used in digital devices.
- Easily manipulated.
Digital:
- Values are limited (0s and 1s).
- Quality is maintained during storage/transmission.
- Needs to be converted to analogue to use in analogue devices.

Analogue data can be captured by an ADC (Analogue-to-Digital Converter) to become digital data.
The ADC converts the analogue signal to digital form; the sound card is an example of an ADC in this context.
The computer receives the converted digital data for processing.

Purpose: Analogue data must be converted to digital data so that it can be processed by a computer.
Process: The ADC takes samples of the analogue signal and converts them to binary code.
Trade-off: The sample rate and a higher number of binary digits (bits) lead to a more accurate representation of the original signal but require more storage on secondary storage.
Notation (conceptual):
- Let f_s denote the sampling rate (samples/second).
- Let b denote the number of bits per sample.
- Higher f_s and higher b improve accuracy but increase data size.
- Resulting digital data rate roughly scales as $R \,=\, f_s \cdot b.$ (conceptual relation; used for intuition in class)

Purpose: Digital data must be converted back to analogue data so that it can be used to drive real-world devices.
Process: The DAC converts discrete digital values (0s and 1s) back into a continuous analogue signal.
Quality: The quality of the analogue signal after conversion depends on the original sample rate and the number of bits used in the digital data.
Conceptual relation: Higher f_s and higher b in the digital data generally yield a smoother, more accurate analogue output.

Emerging technologies are impacting many aspects of everyday life; this section notes the broad relevance of hardware/software concepts to real-world advances and applications.