CSC 1100 Lecture 2: CSC1100-DanO-Session02Notes-2019-0110
19 Feb 2019
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1 of 8
CSC 1100 – Problem Solving and Programming
Session 2 Notes – 10 January 2019
Administrative
Today’s session
Chapter 1 (continued)
– Software and categories
– Computer language (binary)
– Binary units
– Binary, decimal, and hexadecimal number systems
– Data encoding
– Algorithms and pseudo code
Homework 1
Session Topics
Software and categories
● Software is that part of a computer system that you cannot touch.
● Software represents instructions and data.
● There are tens of millions of applications.
● The two primary software categories are:
✓ System software – basic input-output systems (BIOSs), operating
systems, drivers, etc.
✓ Application software – end-user software.
● In the mobile application world, here are the app counts by app store as of March
2018, according to Statista:
Store
OS
Titles (millions)
Google Play
Android
3.8
Apple App Store
iOS
2.0
Windows Store
Windows Phone
.67
Amazon Appstore
(all)
.43
Blackberry World
Blackberry
.23
● The first programmer was thought to be Ada Lovelace. She wrote an algorithm
for Charles Babbage’s Analytical Engine to calculate a series of Bernoulli
numbers.
Computer language (binary)
● A bit is the smallest unit of information processed by a computer.
● Its value is either on or off, 1 or 0, or true or false.
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2 of 8
CSC 1100 – Problem Solving and Programming
Session 2 Notes – 10 January 2019
● This corresponds to an electrical component that may either be on or off, or at
low or high voltage.
● The electrical components of a computer lends themselves to using the binary
numbering system.
● A computer gets all its instructions, and reads and writes all its data, in the
form of bits:
101001101011111110101010101010101010101111101011101
● Since a computer only understands bits, and humans understand characters on a
screen or a page, a conversion is required when the two communicate.
● To enable this communication, every instruction and datum we need processed
by a computer is assigned codes.
● Software automatically:
✓ Encodes our instructions and data in a form the computer can understand.
✓ Decodes data and instruction results from the computer in a form we can
understand.
● For example:
✓ When we type a key on the keyboard, it is converted from a mechanical
signal, to an electrical signal, and then to a stream of zeroes and ones that
encodes the instructions and data we need processed by the computer.
✓ When we print a document, the computer sends out a stream of zeroes and
ones that are converted to electrical signals, and then to mechanical signals
that control where the ink is placed on a page.
Binary units
Data unit
Description
Possible values
bit
Basic unit of data
21 = 2
byte
Group of eight bits
28 = 256
Sample bit
string
0
1
1
0
1
0
0
1
8 bits
bit
bit
bit
bit
bit
bit
bit
bit
1 byte
byte
Metric prefixes
● Metric prefixes enables us to describe large multiples of bytes.
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3 of 8
CSC 1100 – Problem Solving and Programming
Session 2 Notes – 10 January 2019
● There is sometimes confusion when using metric prefixes: sometimes people
mean multiples of 1,000; other times they mean multiples of 1,024. The computer
industry typically means multiples of 1,024 (powers of 2).
Metric prefix1
Approximate size
Actual size
kilobyte (KB)
~thousands of bytes
210 = 1,0241 = 1,024 bytes
megabyte (MB)
~millions of bytes
220 = 1,0242 = 1,048,576 bytes
gigabyte (GB)
~billions of bytes
230 = 1,0243 = 1,073,741,824 bytes
terabyte (TB)
~trillions of bytes
240 = 1,0244 = 1,099,511,627,776 bytes
petabyte (PB)
~quadrillions of bytes
250 = 1,0245 = 1,125,899,906,842,620 bytes
exabyte (EB)
~quintillions of bytes
260 = 1,0246 = 1,152,921,504,606,846,976 bytes
Binary, decimal, and hexadecimal number systems
● Binary numbers can be more readable by converting them to decimal or
hexadecimal numbers.
● Here are the three number systems often used in computing:
Number system
Base
Digits
Binary
2
0 1
Decimal
10
0 1 2 3 4 5 6 7 8 9
Hexadecimal
16
0 1 2 3 4 5 6 7 8 9 A B C D E F
Converting binary to decimal
● To convert a number from binary to decimal, multiply each binary digit by a
power of 2 and add the results together:
Position
…
4
3
2
1
0
Decimal weight
…
24 = 16
23 = 8
22 = 4
21 = 2
20 = 1
Binary digit
1
1
0
1
0
Calculation
(weight x digit)
1 x 24 =
1 x 16 +
1 x 23 =
1 x 8 +
0 x 22 =
0 x 4 +
1 x 21 =
1 x 2 +
0 x 20 =
0 x 1 =
Result
16 +
8 +
0 +
2 +
0 =
26
● So binary 11010 equals decimal 26.
1 The International Electrotechnical Commission (IEC) and other standards
organizations defined a new set of prefixes to directly symbolize multiples of
1,024.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Software is that part of a computer system that you cannot touch. There are tens of millions of applications. System software basic input-output systems (bioss), operating systems, drivers, etc. In the mobile application world, here are the app counts by app store as of march. The first programmer was thought to be ada lovelace. She wrote an algorithm for charles babbage"s analytical engine to calculate a series of bernoulli numbers. A bit is the smallest unit of information processed by a computer. Its value is either on or off, 1 or 0, or true or false. This corresponds to an electrical component that may either be on or off, or at low or high voltage. The electrical components of a computer lends themselves to using the binary numbering system. A computer gets all its instructions, and reads and writes all its data, in the form of bits:
