1.1
bit: binary digit is either one of two digits, 0 or 1
boolean operations: operations that manipulate true/false values are called. AND, OR,
and XOR.
gate: a device that produces the output of a Bollean operation when given the operation’s
input values.
Inputs
AND
Inputs
0
0
1
1
Output
Inputs
Output
0
1
0
1
OR
Inputs
0
0
1
1
0
0
0
1
0
1
0
1
Output
Output
0
1
1
1
NOT
Inputs
Output
XOR
Inputs
0
0
1
1
0
1
0
1
Output
Input
Output
0
1
1
0
Inputs
0
1
Output
1
0
bits were stored in computers using small donut-shaped rings of magnetic material, called
cores, threaded on wires.
capacitor: consists of two small metallic plates positioned paralled to each other with a
small distance between them. charged or discharged. Tend to dissipate on their own,
even while the machine is running. The charge on a capacitor has to be replenished
regularly by a circuit known as a refresh circuit. “dynamic memory” “DRAM”
chip: millions of ting capacitors along with their related circuitry on a single wafer.
hexadecimal: notation: a shorthand notation to represent bit patterns.
example:
10110101 = B5
1.2
RAM (random access memory): main memory: large collection of circuits, each capable
of storing bits. Arrangeed in cells or words. 8 bits = byte. Used to hold data for
processing purposes.
kilobyte = KB = 210 = 1,024
megabyte = MB = 220 = 1,024KB = 1,048,576
gigabyte = GB = 230 = 1,024MB
each cell is assigned a unique name, called its address.
read: asking for the contents of a certain address
write: requesting that a certain bit pattern be placed in the cell at a particular address
left, high-order or most significant bit
right, low-order or least significant bit
1.3
mass storage systems: magnetic disks, CDs, magnetic tapes. less volatility, large storage
capacities, ability to remove the storage medium, greater response times compared to
RAM. Used as a permanent depository for data.
on-line vs offline
CD-ROM can store @ 650MB uses Pits and Lands
CD-R uses dye
WORM = write once read many
DVD can store @ 10GB uses small pits
logical records correspond to natural divisions within the data
physical records correspond to the size of a sector
buffer: a section of main memory used to “unscramble” data retrieved from mass storage
systems.
1.4, 1.5, 1.6, 1.7
ASCII: 7 and 8 bit encoding schemes.
2’s Complement Notation: most popular system for representing integers within today’s
computers
Excess Notation: Another method of representing integer values.
overflow: the problem that occurs when the value to be represented falls outside the
range of values that can be represented.
truncation error or round off error: part of the value being stored is lost because the
mantissa field is not large enough.
nonterminating expansions: values cannot be accurately expressed regardless of how
many digits are used.
Type Name
char
int
short
long
unsigned char
unsigned
unsigned short
unsigned long
enum
float
double
long double
Storage Size
1 byte
2 bytes
2 bytes
4 bytes
1 byte
2 bytes
2 bytes
4 bytes
2 bytes
4 bytes
8 bytes
10 bytes
See “The Binary System”
Range of Values
-128 to 127
-32768 to 32767
-32768 to 32767
-2,147,483,648 to 2,147,483,647
0 to 255
0 to 65,535
0 to 65,535
0 to 4,294,967,295
0 to 65,535
Approx 3.4E-38 to 3.4E+38 with 7 digit precision
Approx 1.7E-308 to 1.7E+308 with 15 digit precision
Approx 3.4E-4932 to 1.1E+4932 with 19 digit precision