Exam (elaborations)
COS1521 Summarised Study Notes
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- University Of South Africa (Unisa)
COS1521 summarized notes for exam preparation. for assistance. All the best on your exams!!
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COS1521NOTES
,Chapter 1 - Introduction
Chapter 1 - Introduction
Key Terms
• algorithm - An ordered set of unambiguous steps that produces a result and terminates in a finite
time.
• arithmetic logic unit (ALU) - Where calculation & logical operations take place.
• computer languages – Any of the syntactical languages used to write programs for computers,
such as machine language, assembly language, C, COBOL and Fortran.
• control unit - Controls the operations of the memory, ALU, and input / output sub-system.
• data processor – An entity that inputs data, processes it, and outputs the result.
• digital divide – A social issue that divides people in society into two groups: those who are
electronically connected to the rest of society, and those who are not.
• input data – User information that is submitted to a computer to run a program.
• instruction – A command that tells a computer what to do.
• integrated circuit – Transistors, wiring, and other components on a single chip.
• memory - Where programs and data are stored.
• operating system – The software that controls the computing environment and provides an
interface to the user.
• output data – The results of running a computer program.
• program – A set of instructions.
• software engineering - The design & writing of computer programs, following strict rules &
principles.
• Turing machine – A computer model with 3 components: tape, controller, and read/write head, that
can implement statements in a computer language.
• Turing model – A computer model based on Alan Turings' theoretical definition of a computer.
• von Neumann model – A computer model consisting of memory, arithmetic logic unit, control unit,
and input/output subsystems, upon which the modern computer is based.
Page 2 of 48
, Chapter 1 - Introduction
Summary
The idea of a universal computational device was first given by Alan Turing in 1937. He proposed that all
computation can be performed by a special kind of machine, now called a Turing machine.
The von Neumann model defines a computer as four subsystems: memory, arithmetic logic unit, control unit,
and input / output. The von Neumann model states that the program must be stored in memory.
We can think of a computer as made up of three components: computer hardware, data, and computer
software.
The history of computing and computers can be divided into three periods: the period of mechanical
machines (before 1930), the period of electronic computers (1930 – 1950), and the period that includes the
five modern computer generations:
1st 1950 -1959: Bulky, used vacuum tubes, affordable only by big organizations;
2nd 1959 -1965: Used transistors, affordable to small & medium sized corporations, FORTRAN &
COBOL were invented;
3rd 1965 - 1975: Integrated circuits reduced size & cost of computers. Software packages
became available, new software industry was born;
4th 1975 -1985: Appearance of micro-computers. Emergence of computer networks;
5th 1985 -> Appearance of laptop and palmtop computers, improvements in storage
media (CD-ROM, DVD), the use of multimedia and virtual reality.
Computer science has created some peripheral issues, the most prevalent of which can be categorized as
social: (dependency, social justice, digital divide), and ethical issues: (privacy, copyright, computer crime).
With the invention of computers a new discipline has evolved, computer science, which is now divided into
several areas.
--ooOoo--
Page 3 of 48
, Chapter 2 - Number Systems
Chapter 2 - Number Systems
Key Terms
• base – The number of symbols in a numbering system.
• binary digit (bit) – The smallest unit of information (0 or 1).
• binary system – A numbering system that uses two symbols: 0 and 1.
• bit – Acronym for binary digit.
• decimal digit – A symbol in the decimal system.
• decimal system – A method of representing numbers using ten symbols: 0 to 9.
• hexadecimal digit – A symbol in the hexadecimal system.
• hexadecimal system – A numbering system with base 16. Its digits are: 0 to 9, A, B, C, D, E, F.
• integer – An integral number, a number without a fractional part.
• number system – A system that uses a set of symbols to define a value.
• octal digit – A symbol in the octal system.
• octal system – A number system with base 8. Its digits are: 0 to 7.
• place value – The value related to a position in positional number system.
• positional number system – A number system in which the position of a symbol in a number
defines its value.
• radix (base) – The base in a positional number system.
• real – A number with both integral and fractional parts.
Page 4 of 48
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