Computer System

The software required to make a computer functional is system software, especially the operating system. It is needed because hardware alone cannot work by itself.

Its two primary services are:
1. To provide services for building and running application programs — it loads programs into memory and allocates the CPU for execution.
2. To provide an interface to the user — it allows the user to interact with the computer through commands, icons, touch, voice, etc.

A computer understands a program written in a high-level language only after it is translated into machine language. This translation is done by a compiler or an interpreter.

- The source code is the program written in a high-level language.
- The translator converts it into object code or machine code.
- The machine code is then executed by the computer.

The execution time of machine code is less than that of source code because machine code is already in the form directly understood by the computer.

Source code must first be translated into machine language by a translator, which takes extra time. After translation, machine code can be executed directly by the CPU, so it runs faster.

RAM is needed to store the program and data temporarily while the computer is working. The CPU loads the required program and data into RAM before processing.

Difference between RAM and ROM:
- RAM is volatile: its contents are lost when power is turned off.
- ROM is non-volatile: its contents remain even when power is turned off.
- RAM is used for temporary working storage, while ROM stores rarely changed permanent instructions such as the boot loader.

The need for secondary memory is to store data, instructions and results permanently for future use.

Primary memory has limited capacity and RAM is volatile, so data would be lost when power is switched off. Secondary memory is non-volatile and provides larger storage for files, programs and results.

Different components of a computer communicate with each other through bus lines.

A bus is a set of physical wires used for data transfer between components. The three buses are:
- Data bus
- Address bus
- Control bus

Together they form the system bus.

The primary role of the system bus is to transfer data, addresses and control signals between the components of the computer system.

- The data bus is bidirectional because data may need to move both ways: CPU to memory for writing, and memory to CPU for reading.
- The address bus is unidirectional because the CPU sends only the address of the memory location it wants to access; the address does not travel back to the CPU.

Freeware is software that is freely available for use, but its source code may not be available.

Proprietary software is software that must be purchased from the vendor who owns the copyright.

Examples:
- Freeware: Skype, Adobe Reader
- Proprietary software: Microsoft Windows, Tally, Quickheal

So, freeware can be used free of cost, while proprietary software is copyrighted and sold by the owner.

The main difference is that a microcontroller is a small computing device with CPU, RAM, ROM and peripherals embedded on a single chip, whereas a microprocessor has only the CPU on the chip.

Smart home appliances use a microcontroller instead of a microprocessor because:
- they are designed for specific tasks only,
- their size and cost are smaller,
- they can work as an embedded controller inside the appliance,
- they are suitable for automatic and repetitive operations.

While browsing the Internet, we deal with different types of data such as:
- text
- images/graphics
- audio
- video
- documents
- web pages

These may be structured, semi-structured or unstructured depending on how they are organised.