Computer language

Published on 12/06/2015 by admin

Last modified 22/04/2025

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1 Computer Language

	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 s
	34 00100010 ″
	68 01000100 D
Hexadecimal 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

Decimal	Hexadecimal	Binary
0	0	0
1	1	1
2	2	10
3	3	11
4	4	100
5	5	101
6	6	110
7	7	111
8	8	1000
9	9	1001
10	A	1010
11	B	1011
12	C	1100
13	D	1101
14	E	1110
15	F	1111
16	10	10000
17	11	10001
18	12	10010
19	13	10011
20	14	10100

Silicon Chips

Components

• A rectangle of silicon (the wafer), forming the base and part of the electrical connection

• 4 or 5 square centimetres (cm) in size

• A layer of active components – containing up to one thousand million transistors

• A layer of passive components – wires

• Round the edge are pads of metal – forming connections

• The layers (or features) are 65–90 nanometres (nm) thick

The Silicon Chip (Microchip)

• Microchips are printed, using a form of photography, through a photo-resist (light sensitive material) and directly onto the chip material

• The final resolution of this process is produced by reducing a large negative to a microscopically small size

• Originally used ultraviolet light as the printing light: giving a final resolution of 1/1000 of a millimetre (mm)

• If beams of electrons are used the resolution is doubled

• Heavy ion imaging produces finer detail and permits ‘ballistic transfer’ of electrons, on a very small chip

Ballistic transfer means that the distances within the chip are so small that the electrons travel like bullets to their destination, without even atoms intervening into their path

• The resultant changes in the photo-resist are removed by a solvent

In a Positive photo-resist the parts exposed are removed

In a Negative photo-resist the unexposed parts are removed

Computer Languages

Machine Code	Historically
Machine Code	• Computer inputs and outputs were on paper tape • Involved calculations • Instructions were turned into binary arithmetic (machine code)
High Level Languages	• A language in which each instruction or statement (in almost plain English) corresponds to several machine code instructions • The most common of the high level languages has become BASIC, initiated by Microsoft • BASIC has many dialects, therefore a program written in one dialect of BASIC will not run on another dialect of BASIC
BASIC Reserve Words (Examples in BOLD)	To enable any computer to RUN it must have some form of language for it to be able to LOAD a program. You may wish to SAVE the program onto disk or tape. It may also be necessary in the program for the computer to READ a set of DATA and, from time to time, GOTO various sections of the program to be able to LIST certain variables which have been turned into STRINGs.
	You may also have to WAIT WHILE the computer WENDs its way through very long CHAINs of numbers before it can RESTORE itself and RETURN to the program and allow you to INPUT more information before it will PRINT out the name you wanted to DELETE. Eventually the program will STOP, END and finally CLOSE.
	• Give a computer specific instructions as to what to do • The Universal language among home computers, mainly due to the simplicity of programming • Unsuitable for large scale programming as, it is very slow as all the instructions have to be translated into machine code by the computer • Programs, written in BASIC are not portable, i.e. they will not run on a different machine
Syntax (Programme construction or rules)	• When programming, exact reserve words and punctuation must be used or the program will not run, e.g. GOTO can only be entered as GOTO, not GO TO • A comma (,) a colon (:) or double quotes (″) are also used
CP/M (A standard ‘business’ computer language)	• Any computer capable of running CP/M is capable of running any program written in that language
DICOM (Digital Imaging and Communications in Medicine)	This is a communications protocol to enable standardisation in medical data files produced and updated by the National Electrical Manufacturers Association (NEMA).
	Aim
	• To integrate information and management systems so that clinical information can be communicated among all specialities and providers • Allow images and data to be exchanged between computers and hospitals • Any doctor will eventually have access to a wide range of tests and images, on computer • The primary concern is patient confidentiality
	It is essential that:
	• Passwords and security systems are regularly reviewed • A system of monitoring the access to each piece of information and producing an audit trail of when the information is accessed, for how long and by using which password is used • All new systems are checked to ensure that they are using DICOM and can be updated DICOM Standards are updated four or five times each year Re-published at least every 2 years
The Problems	Image files
The Problems	• Contain coded data for each pixel that forms the image • Contain a header file, which Contains instructions on how to decode the image This file must be recognised by the system originating the image and the one receiving it If the file is not recognised it cannot be read
Standard File Formats	• The computer language the file is written in should be a standard language • Tagged Information File Format (TIFF) is one of the most common formats • Therefore a TIFF file can be reliably read by most software
Computer Operating Systems	• Include systems such as Windows or DOS • Problems occur if an optical disk is written by equipment from one manufacturer and cannot be read on the system of another manufacturer • DICOM introduces standard operating system protocols to reduce this problem
Networks	• Computers on the same network can transfer files • Problems can happen when trying to transfer files to another network • DICOM introduces standard network protocols to prevent this problem • File transfer protocol (FTP) tends to be the protocol of choice
The System	• Identifies a set of standards • Used by all DICOM compliant manufacturers • Systems from different manufacturers can communicate with each other • The system is made up of fields • Each system has specific information attached as an Application Entity Title (AET), e.g.: Specific hospital Imaging system (MRI, ultrasound, CT, etc.) • Information associated with each image file and how it is formatted is specified • Information objects specify how images from different modalities communicate with each other, e.g.: Outlines what information is contained about the patient (given name, surname, etc.) Object class definition explains the reason for the file, e.g. patient information • Network operations deal with networking protocols
The Manufacturer	• Has to produce a compliance statement for each piece of equipment; this should be available to anyone purchasing that equipment and includes: How the system interacts with communications from a third party Determines the DICOM capabilities of the equipment
Service Classes	• Service classes contain protocols for linking with other systems, e.g. Electronic Health Record Systems or Radiology Information Systems (RIS) with regard to: Producing images Processing images Image display Image retrieval Sending images Image printing Image storage Image queries • Service class users (SCU) Send out information specific to that equipment • Service class providers (SCP) Store images specific to that equipment
Advantages of DICOM	• Allows the integration of network hardware, servers, scanners, printers, workstations from different manufacturers • Better access to images • Time saving – information has only to be entered once • Allows different manufactures equipment to ‘talk’ to each other • Can link with other medical systems (pathology, dermatology, etc.) non-imaging modalities and information systems
Disadvantages of DICOM	• Not all manufacturers fully support DICOM