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Summary Computer Science: An Overview, Global Edition (all chapters)
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Summary Computer ScienceContents
Chapter 0: introduction .............................................................................................................2
Chapter 1: Data Storage .............................................................................................................2
Chapter 2: Data Manipulation ...................................................................................................7
Chapter 3: Operating systems .................................................................................................15
Chapter 4: Networking and the internet .................................................................................19
Chapter 5: Algorithms ..............................................................................................................26
Chapter 6: Programming languages ........................................................................................31
Chapter 7: Software engineering .............................................................................................37
Chapter 8: Data abstractions ...................................................................................................40
Chapter 9: Database systems ..................................................................................................42
Chapter 10: Computer graphics ...............................................................................................44
Chapter 11: Artificial intelligence (AI) ......................................................................................46
Chapter 12: Theory of computation ........................................................................................50
1
,Chapter 0: introduction
Algorithm = a set of steps that defines how a task is performed.
Program = a representation of an algorithm.
Programming = the process of developing a program, encoding it in machine-compatible
form, and inserting it into a machine.
Software = programs and the algorithms they represent.
Hardware = the machinery itself, presenting the software.
Internet = the ability to connect individual computers in a world-wide system.
Abstraction = the distinction between the external properties of an entity and the details of
the entity’s internal composition. Abstraction allows to ignore the internal details of a
complex device (e.g. computer) and use it as a single, comprehensible unit.
Chapter 1: Data Storage
1.1 Bits and their storage
Bits (binary digits) = computer information is encoded as patterns of 0s and 1s (the digits are
called bits). Bits are symbols whose meaning depends on the application at hand. Patterns of
bits are used to represent numeric values or sometimes they represent characters in an
alphabet and punctuation marks, images or sounds.
Boolean operations = operations that manipulate true/false values. Basic Boolean operations
are AND, OR, and XOR (exclusively or). They combine a pair of values to produce a third value.
- AND is designed to reflect the truth or falseness of a statement formed by combining
two smaller, or simpler, statements with the conjunction and. For instance, P AND Q.
Where P represents one statement and Q another. The inputs to the AND operation
represent the truth or falseness of the compound statement itself.
- OR is based on compound statements of the form P OR Q. Statements are true when
at least one of their components is true.
- XOR produces an output of 1 (true) when one of the inputs is 1 (true) and the other is
0 (false).
2
,Gate = a device that produces the output of a Boolean operation when given the operation’s
input values. Gates are constructed by gears, relays and optic devices.
Input values entering one side and the output exiting.
Flip-flop = a fundamental unit of computer memory. It’s a circuit that produces an output
value of 0 or 1, which remains constant until a pulse (a temporary change to a 1 that turns to
0) from another circuit causes it to shift to other value.
As long as both inputs in the circuit in 1.3 remain 0, the output
(whether 0 or 1) will not change. Temporarily placing a 1 on the upper input will force the
output to be 1, whereas temporarily placing a 1 on the lower input will force the output to 0.
Purpose of flip-flop circuit:
1. It demonstrates how devices can be constructed from gates. The flip-flop is only one
of many circuits that are basic tools in computer engineering
2. Flip-flop provides an example of abstraction and the use of abstract tools. Flip-flops
can be build in several manners.
3. It is one storing means within a modern computer
Very large-scale integration (VLSI) is technology that allows millions of electrical components
to be constructed on a wafer (called a chip), is used to create miniature devices containing
millions of flip-flops along with their controlling circuitry.
Stream = a long string of bits
Hexadecimal notation = to simplify the representation of bit patterns; a shorthand notation
1.2Main memory
Main memory = a computer contains a large collection of circuits (e.g. flip-flops), each capable
of storing a single bit. This bit reservoir is knows as the machine’s main memory.
3
, Cells = a computer’s main memory is organized in manageable units called cells, with a typical
cell being size being 8 bits (a string of 8 bits is called a byte. Thus, a typical memory cell has a
capacity of one byte).
- High-order bit / most significant bit = if the content of the cell were interpreted as
representing a numeric value, this bit would be the most digit in the number
- Low-order bit / least significant bit = the rightmost bit
To identify individual cells in a computer’s main memory, each cell is assigned a unique
“name,” called its address. To reflect the ability to access cells in any order, a computer’s main
memory is often called Random Access Memory (RAM). The RAM is constructed by using
analogous, but more complex technologies that provide greater miniaturization and faster
response time. DRAM = Dynamic RAM or SDRAM = Synchronous DRAM. SDRAM is used in
reference to DRAM that applies extra techniques to decrease the time needed to retrieve the
contents from its memory cells.
1.2 Mass storage
Mass storage (or secondary storage) = additional memory devices, which most computers
have, including magnetic disks, CDs, DVDs, magnetic tapes, and flash drives.
- Advantages: less volatility, large storage capacity, low cost
- Disadvantages: requirement of mechanical motion – costing more time to store and
retrieve data and more prone to mechanical failures
Magnetic disk / hard disk drive = a thin spinning disk with magnetic coating used to hold data.
Track = the circle traversed by a read/write head placed above the disk when it spins.
Sectors = the arcs in which a track is divided.
Measurements to evaluate a disk system’s performance:
1. Seek time (time required to read heads from one track to another)
2. Rotation delay or Latency time (half the time required for the disk to make a complete
rotation, this is the average amount of time required to rotate around to read head
once the head has been position over the desired track)
3. Access time (sum of seek time and rotation delay)
4. Transfer rate (rate at which data can be transferred to/from disk)
Flash back memory system = bits are stored by sending electronic signals directly to the
storage medium where they cause electrons to be trapped in tiny chamber of silicon dioxide,
thus altering the characteristics of small electronic circuits.
Flash drivers = flash memory devices, with capacities of hundreds of GBs, are available for
general mass storage applications.
1.3 Representing information as bit patterns (binary notation)
American National Standards Institute (ANSI) adopted the American Standard Code for
Information Interchange (ASCII). This code uses bit patterns of length seven to represent the
upper- and lowercase letters of the English alphabet, punctuation symbols, numbers 0 to 9.
1.4 binary system
4
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