Ch 2Encoding Schemes and Number System — Class 11 Computer Science, concept-first.

Every key you press on a keyboard is in a form you can recognise — letters, digits, symbols. A computer, however, works only in the binary language of 0s and 1s (as seen in the previous chapter).

In the early 1960s, computers could not communicate with one another: each machine represented the keys of its keyboard in its own way, so text produced on one computer meant nothing to another.

ASCII covers English only — so how do we use Indian languages on computers? To make that possible, a common standard for coding Indian scripts, called ISCII — Indian Script Code for Information Interc…

By the time computers had spread across the world, there were many encoding schemes, each covering the character set of a different language.

So far we have seen that each key of the keyboard — a character, a special symbol, a function key — is internally mapped to an ASCII code by an encoding scheme, and that this code is then converted to…

The decimal number system is the one we use in day-to-day life. It is known as the base-10 system, because it uses 10 digits — 0 to 9.

Why do computers count in 0s and 1s at all? The answer lies in the hardware. The ICs (Integrated Circuits) inside a computer are made up of a very large number of transistors, which are activated by t…

As the value of a decimal number grows, the number of bits (0/1) in its binary representation grows with it.

Like octal, hexadecimal numbers are used for a compact representation of binary numbers — and they compress binary even further.

Where does hexadecimal actually get used? Two everyday places: memory addresses and web colours. Both are cases where humans must read long binary values, and hexadecimal makes them manageable.

We now know the four number systems used in the context of computers. The natural next step is learning to convert a number from one system to another, which is essential for understanding how numbers…

One single procedure converts a decimal number into any other number system — binary, octal or hexadecimal. Only the divisor changes: it is always the base value (b) of the target system.

The reverse journey — from binary, octal or hexadecimal back to decimal — uses the positional-value idea from Section 2.2.

Converting between binary and octal/hexadecimal never needs division or positional sums — it is pure grouping and substitution.

All the conversions so far dealt with whole numbers. Numbers with a fractional part need one extra set of techniques — and there are three cases to master.

- An encoding scheme maps text into codes, which is what makes communication among computers possible — every key pressed is mapped to a unique code value, which is then converted to binary.