CMSC 104, Section 301, Fall 2002
1
Lecture 03, 9/09/02
Operating Systems and Using Linux
Topics
•Review Number Systems.
•Go over Homework 1 Solution.
•CSHC Hours of Operations.
•What is an Operating System?
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
The Number System
Position Number System
•The same digits have different meaningdepending on their position in the numeral.
•The value of a digit depends on the digititself of its position.
•Binary, decimal, hexadecimal are allposition number system.
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
The Number System (con’t)
•Example:4410
101 100
4 4
------------
4 x 10 + 4 = 4410
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
The Number System (con’t)
Binary Decimal Hexadecimal Binary Decimal Hexadecimal
0 0 0 1010 10 A
1 1 1 1011 11 B
10 2 2 1100 12 C
11 3 3 1101 13 D
100 4 4 1110 14 E
101 5 5 1111 15 F
110 6 6
111 7 7
1000 8 8
1001 9 9
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
Converting From Hexadecimal to Decimal
•Example: Convert 1A5F16 to decimal.
1 A 5 F
163 162 161 160
4096 256 16 1
Recall: A16 = 1010 and F16 = 1510.
= 1 x 4096 + A x 256 + 5 x 16 + F x 1
= 1 x 4096 + 10 x 256 + 5 x 16 + 15 x 1
= 4096 + 2560 + 80 + 15
= 675110
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
Converting From Decimal to Hexadeciaml
•Perform successive divisions by 16, placing theremainder (0-9, A-F) in each of the positions from right toleft.
•Continue until the quotient is zero.
•Example: Convert 14310 to hex.
143 / 16 = 8 rem = 1510 = F16
8 / 16 = 0rem = 8
Done answer = 8F16
To Check: 8 x 16 + 15 = 128 + 15 = 14310
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
Example of Equivalent Numbers
Binary: 1 0 1 0 0 0 0 1 0 1 0 0 1 1 12
Decimal: 2064710
Hexadecimal: 50A716
Notice that the number of digits neededis smaller as the base increases.
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
Homwork Solution 1
Go over homework solution 1!
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
Operating Systems and Using Linux
Topics
•What is an Operating System?
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
Computer Science Help Desk
• CSHC (Computer Science Help Center)is staffed by student tutors.
• Help with homework and projects.
• Text editors and Linux questions.
• ECS 332A – Hours of Operations:
• Monday – Thursday 12 - 8 PM
• Friday 12 – 4 PM
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
What is an Operating System (OS)?
• A computer program
• Performs many operations, such as:
• Allows you to communicate with the computer(tell it what to do)
• Controls access (login) to the computer
• Keeps track of all processes currently running
• At this point, your main concern is how tocommunicate with the computer using the OS.
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
How Do I Communicate With the ComputerUsing the OS?
• You communicate using the particular OS’s
user interface.
• Graphical User Interface (GUI) - Windows
• Command-driven interface - DOS, UNIX,
Linux
• We will be using the Linux operating system,
which is very similar to UNIX.
CMSC 104, Section 301, Fall 2002
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Lecture 03, 9/09/02
How Do I Communicate With the ComputerUsing the OS? (con’t)
• When you log in to the Linux system here, a user
prompt will be displayed:
linux#[1]% _
where # is the number of the Linux server that you haveconnected to. You may use any of the Linux servers.
• The number in the brackets will change as you work. It is
the “number” of the command that you are about to type.
• If this prompt is not on the screen at any time, you arenot communicating with the OS.