Computer language

1 Computer Language

How Computers Work

	Keyboard Each key represents a number of electrical signals (a stream of electrons and spaces)
	To input data A key is depressed
	For each key depressed A number of electrical impulses (signals and non-signals) are sent to the computer
	Silicon chip The circuits on the silicon chips are activated
	Signal A corresponding signal is sent to the screen (composed of signals and non-signals)
	Image formation When an electron interacts with the screen the screen fluoresces When there are no electrons it does not fluoresce
	Example image of a letter T
	111111
	001100
	001100 Where 0 = no electron and 1 = electron
	001100
Decimal System	• To base 10 • Each column represents an increase by a factor of 10, e.g. ten (10), hundred (100), thousand (1000), etc. • This system is too complex for computers to handle in this format
Binary	• To base 2 • Each column represents an increase by a factor of 2, e.g. two (2), four (4), eight (8), sixteen (16), thirty two (32), sixty four (64), etc.
	A 64 32 16 8 4 2 1 = Decimal numbers
	B 1 1 1 0 1 1 0 = Binary number
	C 0 1 0 1 0 0 1 = Binary number
To Change Binary to Decimal (This can be done automatically by using a computer’s Scientific Calculator)	Example 1
	• Take row B above and read off the corresponding numbers in row A • = 64, 32, 16, 4, 2 • Add the numbers together = 118 • Therefore 1110110 = 118
	Example 2
	• Take row C above and read off the corresponding numbers in row A • 32, 8, 1 • Add the numbers together = 41 • Therefore 0101001 = 41
To Change Decimal to Binary (This can be done automatically by using a computer’s Scientific Calculator)	128 64 32 16 8 4 2 1
	Example
	To change 118 to Binary

• 118 is smaller than 128 therefore = 0

• 118 is larger than 64 therefore = 1 (118 – 64 = 54)

• 54 is larger than 32 therefore = 1 (54 – 32 = 22)

• 22 is larger than 16 therefore = 1 (22 – 16 = 6)

• 6 is smaller than 8 therefore = 0

• 6 is larger than 4 therefore = 1 (6 – 4 = 2)

• 2 is the same as 2 therefore = 1 (2 – 2 = 0)

• 0 is smaller than 1 therefore = 0

The binary number is therefore 01110110

Bit
(BInary digiT)

• The smallest piece of information that a computer can handle

• Represented by a simple electrical signal

• Which is either ON or OFF

• 0 represents OFF

• 1 represents ON

Byte

• Equals 8 bits

• Can represent numbers 0 to 255 inclusive

• Which is 256 different combinations of ON and OFF

• The main use for the numbers 0 to 255 is in the ASCII code (The American Standard Code for Information Exchange) to designate numbers, characters and symbols used on the computer keyboard

Example[Decimal] [Character] [Character]115 01110011 s34 00100010 ″68 01000100 DHexadecimal System

• To the base 16

• Using numbers 0 to 9 and letters A to F

• Therefore representing large (decimal or binary numbers) with fewer characters

• Conversion can be done automatically by using a computer’s Scientific Calculator up to a maximum of 16 digits using Qword option

Table 1.1 Comparison of decimal, hexadecimal and binary number systems 0–20

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