Ch 1Computer System — Class 11 Computer Science, concept-first.

A computer is an electronic device that can be programmed — it accepts data as input, processes that data according to instructions, and produces a result as output.

The Central Processing Unit (CPU) is the electronic circuitry of a computer that carries out the actual processing of data.

Input devices are the devices through which data and control signals are sent into a computer. Whatever a user wants the computer to work on — text, clicks, images, sound — must first enter the system…

An output device is a device that receives data from the computer system and presents it to the user — on a display, as a physical printout, as sound, and so on.

Computing devices have travelled, in a relatively short span of time, from simple mechanical calculators to today's powerful data processors.

A computer system needs memory to store the data and the instructions it is going to process. Nothing can be computed until both the program and its data are held somewhere the CPU can reach.

A computer system stores and processes everything using binary numbers — sequences of the digits 0 and 1. The units in which memory is measured are therefore built up from the binary digit itself.

Human beings memorise many things and recall them to make decisions — but we do not rely on memory alone; we also make notes and store important information in notebooks, manuals, journals and documen…

Processing constantly moves data around inside a computer: between the CPU and primary memory, and between primary and secondary memory.

In earlier days, a computer's CPU occupied a large room or several cabinets. Advances in technology have shrunk that same functionality onto a single microchip.

Microprocessors are classified and compared on the basis of a handful of key features: chip type, word size, memory size, clock speed and cores.

A microcontroller is a small computing device that has a CPU, a fixed amount of RAM, ROM and other peripherals all embedded on a single chip.

A computer exists primarily to process data. From the computer system's point of view, everything is data — instructions, pictures, songs, videos, documents, all of it.

A computer system receives raw data — facts, concepts, instructions — through its many input devices. Internally, everything is stored in binary form (0s and 1s); but externally, data can be entered i…

Before data can be processed it has to pass through a life-cycle: it must first be captured (input), then stored in a file or database for future use, and finally retrieved from that store whenever pr…

One of the biggest threats to digital data is its deletion — and deletion can happen in several ways:

Everything studied so far — CPU, memory, buses, storage, input/output devices — is the hardware of the computer system: its physical components. But hardware on its own is of no use.

The sole purpose of software is to make the computer hardware useful and operational. Hardware is inert circuitry; software is what brings it to life.

System software is the software that provides the basic functionality to operate a computer by interacting directly with its constituent hardware.

To get work done by a computer, we must give it instructions to apply to the input data. Computer languages exist for writing those instructions.

System software provides the core functionality of the computer system — but different users need the computer for different purposes.

Software also differs in how it is released and licensed — whether you can see its source code, whether you must pay for it, and what you are allowed to do with it.

An operating system (OS) is best thought of as a resource manager: it manages all the resources of a computer — the hardware, including the CPU, RAM, disk, network and the other input-output devices —…

Operating systems offer several different kinds of user interface, each providing a different way for the user to give commands.

Behind its user interface, the operating system performs the management services that keep the computer running.

- A computer is an electronic device that can be programmed to accept data (input), process it, and generate a result (output); together with its hardware and software it forms a computer system.